Lithium Cells in Float Charge. Will it destroy your battery?
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- Опубліковано 29 вер 2024
- Can you float charge lithium batteries? Should you float charge lithium batteries? What are the best settings for your charge controllers? Will float charge destroy your cells?
I played around with a lot of solar charge controllers trying to understand and find the best absorption and float charge settings. It can be very confusing and it's a bit hard to fit this all in one video. Please let me know if you want to see more details about a specific setting and how this works out in reality. I will break this down and make a separate video about that then...
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Another great video. You explained it well. I tend to think of the float voltage as mainly keeping the cells at a pretty high state of charge, and allowing you to run loads off the solar power when you have good sun. As you said, if you use either no-float (my CC does provide a 2-stage with no-float) or a really low float, you are missing out on using the sun when you have it.
Late to the party here, but here is a perspective you may have missed, and that is charge current... So I want my batteries to charge to 3.4V, however when I set my charger to this voltage as we approach this voltage the current in the battery will start to drop, eventually reaching 0A at 3.4V when the battery is fully charged. This will take a long time. So I set my boost charge to 13.8V so that I can make maximum use of available charging power and keep the current high even at the desired 13.4V. Yes it means I am "over charging" my batteries past my target for a few hours, but at least I charge as fast as possible. Then when we switch to float charge, my loads will bleed off the excess charge and we will then reach my desired 13.4V and solar will kick in an supply the load. This way I get my batteries charged as fast as I can to take advantage of available sun.
Nice video. Lithium batteries have been around for decades now so there's no excuse for these charge controller companies not to have a lithium battery setting that ELIMINATES all the old lead acid terminology and just uses the correct lithium battery parameters. Then you could simply edit them per your particular lithium battery manufacturer's recommended settings. All this "float", "boost", and "bulk" stuff is useless and misleading.
no. the terminology is still correct. only the electric physic is important to management of the battery. if you reason by terminology or name of algorithms, then you dond understand the basic of electricity, like ohm laws
@@fc436 Nope, he is correct. Terms like float do not work with LFP so should be avoided. They only confuse things. If the voltage drops under the treshold then the charging should start.
Good video mate :-)
I have run my offgrid LFP bank (nearly 8 years ) in pretty much the same way.
There is some research suggesting that the "mini" charges that the "float" setting does detracts from the cycle life more than if you could do one or two top up charges per day.
So if the Charge controller, after bulk ("Top Up") charge cycle, could just supply make up current so the battery was not getting discharged - (but at the same time not charging the battery). .Then either at a lower threshold voltage or time (3PM in Brisbane) , the "Top Up" cycle could recommence.
This will be the way I'll do it in the next incarnation of my system.
Thank you simplified for us novices.
Thank you for this very comprehensive explanation. It is very helpful in setting the right parameters for my new 16s2P liFePO4 battery bank. Nowhere else I could find such a good explanation.
I have 2 6volt golf carts at 12v and wanted to add 16s lifpo4 in series par 12 volt . so sounds like 12.4 trickle is ok am i getting this right thanks in advance
Great info. It's the exact video I needed to watch. Very important to know this about float voltage. Thanks, man.
No problem! Thank you.
If you have an active system with an inverter running 24/7 with intermittent loads like a fridge the idea of float could be revisited. It depends on your application as to whether float could be used.
How exactly would it differ? I ask because that is my case.
@@XcarecaX the reason for float is to replace the charge in the battery as it falls below the set point. With a lead acid battery this mean the battery is fully charged when the sun goes down. Before I put my lithium batteries into service this seemed like a desirable feature. However I’ve found that the lithium batteries work a lot like a power tool battery. They are fully charged and then the charger is removed allowing the batteries to be used until they need to be charged again. I’m still running a refrigerator, separate freezer, water pump and several little chargers no problem. In a days time I use about one hundred amp hours of three hundred in the battery bank. This has actually worked out very well for me. I didn’t like the idea at first but now accept it as the proper way to use lithium. So…. I no longer see the benefit of trying to float the lithium batteries.
@@jamespayne8781 That approach is good, but depends on having enough battery to pull it off and/or having a reliable charge source that won't go away. In my case my battery bank will only run my fridge for 2 days, even less in hot weather. So I don't want to be wasting sunshine and solar power just to optimize the abundant battery cycles. I need my panels to be powering my fridge and to end the day with a full-ish (not 100% unless it just got there) battery bank in case it's the last sun I'll see for a while.
@@ceeweedsl I think most of us are still sorting out the truth about lithium cells and how to charge them and use them. There’s a lot of information and miss information on UA-cam and the internet in general. I’m still looking into the idea of floating lifep04 batteries though I don’t really need to currently. I read on the Battle Born site that you can float them. There’s considerations though. One consideration is there needs to be a constant draw on them as in my original thinking. You wouldn’t want to float fully charged cells.
@@jamespayne8781 Sounds right. I think the biggest take away in this video is that no current is actually entering the battery in float mode UNLESS it drops below Vfloat. So, one could say it's in float mode, but it's not actually getting any current into the battery, so it's more of a standby there to power loads. The undesirable part about floating is pushing current into the battery after it's been brought to full. But if the voltage is set low enough, there's zero to nominal actual current pushing into the cells. That's my understanding.
What I'm trying to point out is that your cool power tool analogy/ approach is probably optimal IF you've got plenty of battery to spare and can afford to sacrifice storage capacity available at the end of the day. Then you can just charge to full, ignore any further sunshine and start draining.
If your storage is closer to what you need to run things, then it's different and you need to make use of that sun to power things while it's out and save the most capacity possible for after dusk. I can't fit any more battery into my van! Gotta milk what I've got for what it's worth! Good to know that I'm not really abusing the cells to keep float at resting V.
So based on this video, what setting should I use among this once this inverter/charger has no other option?
1) 14.0 - 13.7
2) 14.1 - 13.4
3) 14.6 - 13.7
4) 14.4 - 13.6
5) 14.4 - 13.8
6) 14.8 - 13.8
7) 15.1 - 13.6
Thank you!
Good information! I will set my two Epever 40A controllers accordingly. Another great video! I might get a Victron. I would like one or two 150V controllers.
Thank you. I still have to try the Epever but al reviews are very positive.
Hi Peter, also look into Outback Power MPPT's. I have had 2 x 80 amp units running for over 10 years in the Qld summer with no problems. Oh except replaced a cooling fan in one.
@@ElectricCarAustralia Yes, I've heard great things about Outback. Thank you!
how to set the control parameters EPEVER? Which entries do I have to make for OverVoltDisconnect, OverVoltDeconnect, BoostChargingVolt, FloatChargingVolt, BoostReconChardVolt LowVoltReconnectVolt. I have 16s 3.2V 48V Lifepo4 200A = 10kW
Video davvero bellissimo e molto interessante, ti ringrazio della spiegazione. Complimenti sei davvero molto preparato.
great work as this is the same system i need. can we see the frog ???
Sure...
This is hilarius in Chile because we have some viral video about "dirty frog"
Victron, sehr gut! Hab hier den EPEver, warte aber noch auf meine Batterien.
I thought you were supposed to let your batteries discharge by using them until they reach a certain lower level and then they will automatically start charging again. From everything I’ve heard you don’t want these batteries to stay for all the time they are meant to be drained and recharged so what’s the real deal
I am faced with a similar situation, have a low capacity solar input with a max Ipv of 0.33A in full sun. I want to float my LIFePO4 cell bank to capture all the PV energy when needed to keep the cell pack fully charged. But there is no need to capture excess PV energy after the pack is fully charged. The pack is an 8S configuration. using 6AH cells. It runs an driveway gate and its controller. The gate motor draws about 2-3A for 25 seconds a few times a day and the controller about 10mA continuous. The battery data is silent on float voltage but full charge is listed at 3.65V and max at 3.7V. Very little data exists on floating (not in the lead acid sense) for LIFePO4 cells, found only a couple of references to floating at 3.40 to 3.45 per cell. What I discovered in testing the cells, was as the cell voltage approached 3.45V the current flow into the cell reduced to zero. My bench supply was set to 3.45V per cell with a current limit set to .33A. Thus at the 3.45V the power supply is running in a constant voltage mode. The implication of no current flow suggests the charge voltage of 3.45V exactly matches the cells chemistry emf value. Thus I can't see any reason why the cell could not remain in this state indefinitely without harm. If the battery becomes discharged to a point the terminal voltage is below the 3.45V then current will flow into the battery again to replaced the used energy. I believe you need to be accurate with your voltages and pay attention to voltage changes with temperature. In my case I decided to use an accurate shunt regulator to set the PV array output voltage to 3.45V/cell. With this setup the charging will be CC (constant current) limited by the PV max output of .33A (.05 C) when the cell voltage is below 3.45V and switching to CV (constant voltage) when the battery absorbed charge current drops below the PV output current.
What I think would be really bad for the cell would be to trickle charge the cells like a LA battery, using a constant current source set to low amperage.
Would be interested to see some definitive data about the issue.
Yeah... float charging is a bit of a misnomer in this case, because there is so little voltage deferential, the pressure keeping something afloat with a trickle current, wind in the sail, or whatever analogy you might prefer. Maybe it should be called loft charging, due to it having a set level even when there is insignificant current? 🤔
in lead batteries the floatimfg is used for 3 things
1) avoid self-discharge when using a buffer
2) complete the last 1% of charge that cannot be reached in the absorption phase
3) balance the cells
In lifepo4 batteries there is no need for the floatimg voltage to continue charging.
But it is only needed so that the generator in parallel with the battery (solar, alternator, wind, grid) can power the loads without discharging the battery uselessly.
In the typical solar example in a camper, where the lifepo4 battery is already charged at midday.
There MUST ABSOLUTELY BE A FLOAT VOLTAGE THAT PREVENTS THE BATTERY FROM DISCHARGING WHEN THE SUN IS PRESENT.
This float voltage must be identical to that of the charged open-circuit battery. In this way there will be no chemical charging activity or current input to the battery. But the solar generator will power any load as long as it has enough current to maintain that float voltage. Afterwards, when the current is not sufficient, the battery will begin to contribute.
Otherwise, people who think like you argue that a lifepo4 battery in a solar cycle must start to discharge as soon as it is finished charging, even if there is enough sun for the loads. and do a thousand small charge and discharge cycles every day.
The equalization voltage is used to balance the cells in LA batteries. You basically overcharge the battery to achieve that and top balance them. They won't balance in float mode, the voltage is not high enough.
yes
@@OffGridGarageAustralia
Excellent! You provided exactly what I was looking for. Thank you.
All correct info however factory built lithium battery with bms has a top or bottom balance system so if you keep the hi voltage to low the cells go out of sink witch is not good
Hi , what should I set my Epever controller to for my lithium batteries , does it have a lithium setting 🤔
So how do you tell when a LifePo4 battery is fully charged? Is it when it reaches 13.5v, when it has settled at 13.5v after removing it from the chrager? My 200ah Voltax battery says its charge voltage is 14.6v but it seems to want to return to around 13.5v when it is removed from the charger. I have a Victron 100/20 charger and that did what you did when set to 13.5v does that mean the battery is fully charged? why does it say the charging voltage is 14.6v does that mean you are meant to set the victron to 14.6v in the Lifepo4 setting?
So we have a sailing boat. It has a AGM battery to start the engine and a LiPo4 for the house supply. The engine is fitted with an alternator controlled by an external (adjustable) regulator. There is also a small solar array with mppt controller. Power from the alternator goes through a diode splitter to charge both batteries. Where should the mttp output be connected? Can it be connected before the diode splitter as per the alternator output. What voltage parameters should be set? Should the regulator be set the same? Of course the desire is to maintain the AGM and recharge to lithium to to provide best capacity.
QUESTION; I assume you can charge a LifePO4 with a standard charger, but understand it will not charge to full capacity? I plan to have 2 x 230 amp hour batteries, what kind of stand alone charger do you recommend?
I’m rather confused, my new kings 200amp lithium batteries says that the maximum charge voltage is 14.6 v
Float charge is 14.4v
What should I be setting my victron settings to??
Hi Andy...I have following question. My battery pack is 24v/ 400ah. Can you advise me what is the best bulk and floating charge voltage I have to set at my charge controller
With a 24V LiFePO4 battery I would use
Bulk Voltage 27.6V (also start balancing here)
Float Voltage 26.8V
Brilliant. So thorough, so helpful!
Andy, my lifepo4 with Victron 100/30 restarts a bulk charge every morning while the voltage is still on par with float.
I do not understand why. It doesn't need to try bulk and start absorb (20min as per my settings). I only use it in weekends at the off-grid cabin this is 5x needless absorb started. Why does Victron do that?
The MPPT resets every night and always starts a new cycle in the morning. Set the Absorption to 55.2V (1h to allow balancing, no tail current) and float to 53.6V, re-bulk to 1V.
This will keep the battery happy and balanced.
Hey, not too new but still a great video. Do you have any experience with AliExpress's chinese Liitokala batteries? It says that balancing starts at 3,5v. So should i set absortion to 14v, and let it balance for a couple hours before it starts floating at 13.5v?
Thank you for sharing your experience. They are very valuable. I have Victron Multiplus 12/3000 Inverter-Charger and there's a "storage" charging cycle. Is this the same as float charge? The refrigerator on my boat works off 12v after the smart shunt. So the Inverter-Charger keeps sending current to the shunt because the refrigerator is consuming power. Should Absorption be 13.4v and float/storage be 13.2v ? Thanks so much.
As long as the floating voltage is at or below the 100% state of charge it will not change the batteries beyond that point, if you have set up your batteries to stay between 20 - 80% state of charge floating your batteries is absolutely fine and will keep them topped up if you intent to leave them alone for a long priod of time, and really you shouldn't be charging your batteries to 100% SoC and discharging them to 0% SoC basically ever, you should always leave at least like 10% and charging to 100% should only be done rarely to top balance the cells.
If your not working with raw cells and are working with a high quality server rack battery, powerstation or drop in replacement lithium car battery the BMS will generally at least limit you to 10% SoC and may even limit you to 10% and 90% or for batteries with a stated cycle life of 5000 cycles or more without the caveat of 20 - 80% SoC they will limit you to cell charge states of 20 to 80% to achive that 5000+ cycles to 80% capacity.
Most cell manufactures recommend that you only charge to 80%. It will greatly increase you charging cycles.
Well, that is only true for Li-ion cells though. The problem is not the SOC but the voltage you run the batteries on. The higher the voltage, the higher the degradation. We can charge LFP cells to almost 100% with a low voltage and enough absorption time. You cannot do this with Li-ion cells as they will just stop charging.
Wow so correct, no current demand from fully charged lithium at the fully charged voltage = no charging current simple as that, the only reason lead acid floats is its internal resistance make it demand all the time even when it hits full voltage.
Is 13.4v really about 80% as he claimed?
Everything I've seen states that 13.4v is more like 99% and it reduces the life of the cells.
Is this a difference between charging voltage and a settled voltage after a while without charging or loading?
I take from your video that LiFePO4 batteries will just stop drawing current when it reaches a particular set voltage. However, I have a travel trailer I upgraded to LiFePO4. When the RV is plugged in at home or at a campground, I must provide a constant (12v) voltage to power lights, refrigerator, etc... So the batteries are receiving a constant float voltage for long periods of time. In the long term; weeks to months, will float voltage damage the batteries?
Hey! Please help me with something. I whant to put in parallel and series 4 pieces Agm 120 amp each and 4 pieces lipo4 200 amp each. A sistem with 24 or 48 volts. Charged from solar panels. I have a mppt. And olso pwm. But you know how will be toghether Agm and lipo4?
Question for the expert: I have a sunsynk inverter (3.6kW) and two Tesla 5.3kWh batteries connected in series. There is no BMS programme for the Tesla batteries in the sunsynk library, so I have connected it as an AGM battery (as they advise). According to the manufacturers specification the maximum voltage for the 2 batteries in series is 50.4 volts, however when there is power flowing from the pV panels the battery easily reaches 50.4V and keeps accepting charge. Should I limit the charge voltage on the inverter to 50.4, or can I just let it keep charging until no more power flows? Or will that wreck the batteries or blow them up? They have been working for 4 months now no problem, but I can only input 6.2 kWh so I am not using the full capacity. Thank you for your help because if you cannot help me who can?
Thank you.
Test the elejoy 600 watts it has a set voltage
If MPPT does not charge battery because of low float setting the energy will directly to the inverter correct?
Yes, that is correct, the power from the solar panels goes directly into your load if needed there.
The MPP isn’t floating like you’re saying… we are using our batteries with inverters connected and item running using power and the MPP is maintaining a set float voltage because are using and draining those batteries
Great video, I'm learning a lot from them all, thank you for all the time and effort you put in. Sounds like for Li batteries the 'float' is essentially a 'minimum threshold' and the absorption is the 'maximum threshold' you want your batteries to be at? I wish I had a more direct charge controller on my laptop!
Yes, that is correct. At least with most charge controllers. The JNGE seems to work differently
Sir if I connect Lifepo4 in normal inverter with float charge. That will not damage the battery and work fine. As per your video I guess so. Pls clarify
What voltages are you operating with? What kind of battery voltage and controller voltages have you set?
@@OffGridGarageAustralia sir it's having the voltage set of 13.6v (2.2v/cell) as maximum and then cut off automatically by bms in 12V system. It's a lead acid based ups so it will start charging the battery as low as 10.8 (1.8v/cell). Is the range is fine? And if we give higher voltage in bms what will happen it will cutoff or charge the battery (i.e charge 12.8v Lifepo4 with 18v eleminator)
My inverter dont have lifepo4 battery option, can i set it on agm? Is it good or bad?
Thank you. So can you set float charge to 100% (14.3 or 14.4 whichever) rather than just the 75% (13.3v) which you did in your experiment. Then the battery always returns to full charge.
I'm still sorting this out after years of running my system but I'd say no, don't set float much above 13.5 At some point you are forcing your battery too stay too high. They don't really like to sit at 100%.
Would a lead acid smart charger set to gel would that be safe no solar
what do you set the generator settings to?
What generator settings?
Can you set the charge to 14 volts
Constant charge...? For Lithium LiFePO4 batteries
And is this a bad Idea...?
Just a side note, once you've charged a LiFePO4 (and I think other lithium types too) up, say up to 13.8V or 14.0V and then stop applying voltage, the battery voltage will actually drop down to around 13.6V fairly quickly (well, probably closer to 13.55V). It remains fully-charged, that's the just the natural stable voltage for 4 x fully charged cells. So don't be surprised if you charge the battery up higher that you see it drift back down to that voltage. It just doesn't take a whole lot of current for the voltage to almost instantly drop back to around 13.55V. It can happen fairly quickly (depending on the BMS's vampire draw) even if no load is attached.
So, for absolutely definitely sure, never set the float voltage above around 13.55V... that will cause the charge controller to apply a little current quite often due to the battery wanting to return to its stable voltage... and that is bad for the battery. And, of course, as the battery ages, even 13.55V will cause a constant current. Hence you probably shouldn't set the float above 13.4V or so regardless... and lower values are even safer. Up to a point.
Remember to use the discharge curve, NOT the charging curve, to figure out what float settings you want.
This means that, in fact, if you charge the battery up to 100% and start discharging it with the float set to 13.4V, the battery will still remain at least 90% charged as the charge controller starts matching amps below 13.4V against the load. However, if you discharge the battery sufficiently and the charge controller does not go back into BULK mode, then the battery's charge level will probably sit at just below 90%.
So, to figure out the worst case charge level for the battery, you want to look at the discharge curve and at the voltage point where the charge controller switches back into BULK charging mode. So lets say float is set to 13.20V and the charge controller flips back into BULK mode at 13.10V. Thus, 13.10V on the discharge curve is the worst case charge state that the battery will ever be left in... lets call it 50%. Definitely NOT ideal.
--
This creates a conundrum. If you set the float TOO low, the worst case state of charge that the charge controller might leave the battery in will be too low. Things can get iffy below 13.2V, so my recommendation is that the float be set at roughly 13.4V in order to ensure that the charge controller goes into bulk at a reasonable voltage (say, 13.3V, depending on the charge controller). This way if the voltage only drops to 13.31V and the charge controller stays in FLOAT, the battery will still be at around an 80% state of charge.
You can safely set the FLOAT voltage to anything under 13.55V for a new battery, but to deal with battery aging you should consider not setting it higher than 13.45V or so. If you want to be conservative, then use 13.3V or 13.35V. I would not recommend 13.2V for the float because that means the battery could be seriously discharged before the charge-controller decides to go back into BULK mode. The state of charge drops precipitously enough below 13.3V that you just can't depend on setting the float below that voltage.
This is why the Victron's Float is set at 13.30V. Its a good conservative value that will deal with battery aging but isn't too low to cause the battery to be left in too-low a state of charge when it could be charging.
Now Bulk and Absorption are a different matter. In order to charge the battery, voltages in excess of 13.6V are required. 14.0V is a typical target voltage for BULK. Absorption is basically irrelevant... so set the voltage to something inbetween Float and Bulk Target and then set the absorption time to 0. HOWEVER, on some (most?) Victrons, the Absorption *IS* the bulk target voltage. Therefore, you should set Absorption to 14.0V (for roughly 80% charge) and set the absorption time to 0. If the Bulk target (or Absorption, depending) on the Victron is set too low, and the battery is being charged up from a low state of charge, it will probably never reach even 50% charge before the charge controller decides it is done.
Once LiFePO4 reaches the target voltage during charging (Bulk target of 14.0V or so for 80% charge), the charge is done. The battery will remain at 80% charge even as its voltage slowly drops back down to 13.55V, and the percent-charged during discharge will head south from there on down. When you are discharging the battery, you should refer to the discharging voltage curve and not the charging voltage curve.
This target voltage is really what you are comfortable with. Most people use 14.0-14.2V. Use 14.6V only if you want to actually charge the battery to 100% (most people do not as this reduces the life of the battery).
This is my understanding.
-Matt
Thanks so much Matt. These are the comments we need with good, easy to understand explanations and examples. Great.
I have planned to set the absorption to around 3.35V-3.37V and the floating just a tiny bit lower. As there will be more batteries following in the future, I'm not planning to charge them to 100% on a regular base. Maybe once in a while to do a test or so but I try to keep them between 85-90%. The same at the bottom, going below 3.1V is almost pointless, there is almost no capacity left und voltage will decrease very quickly under 3V anyway.
@@OffGridGarageAustralia Yup. Maybe even slightly higher. The exact setting will depend on the device's voltage measurement error. This might be why identical settings in the two charge controllers you tested yielded different results.
The voltage sensors used by charge controllers, BMSs, etc, particularly cheap ones, typically have around a +/- 1% error factor. So the settings on one charge controller verses another may not manage the battery to the same exact targets. 1% is massive. e.g. at 13.0V the error is +/- 0.13V. Very significant. Higher quality equipment might cut that error in half, and if really done properly the equipment will be factory-calibrated and the firmware will temperature-compensate readings to get the voltage sense error below 0.3%.
The balance lead voltage sensors are usually a bit more accurate but even so we're still talking 0.5% or so (0.016V @ 3.35V). On a cheap BMS even these are probably only 1% accurate. They can still balance the cells because the same inaccurate circuit is typically round-robined across each pair of balance leads, so the error winds up being the same for each pair.
But in terms of relying on absolute voltage readings, you need to take some care when dialing in settings.
How to get a more exact voltage reading? Difficult. A typical Multi-meter is usually calibrated to 3.5 digits or so... roughly 0.5% accuracy. Getting higher accuracy gets expensive real quick.
--
Hence why it is a good idea to do a real capacity test with your charge controller settings to make sure its doing what you want it to do. These are longer tests (I'm specifying for LiFePO4).
(1) Discharge the battery to 50% or lower, charge it up with the charge controller, then do a full discharge capacity test to the low voltage cut-off. Record the resulting Wh.
(2) Charge the battery up with the charge controller, then apply a current-limited 14.6V to the battery with a power supply (limit current to 0.5C) and watch it like a hawk until the current begins to drop off to see how much more the battery could have taken. Record the resulting Wh that was additionally charged.
And from those two results you will know what the charge controller is actually charging the battery too.
-Matt
@@OffGridGarageAustralia One other thing to keep in mind is that there is a voltage barrier somewhere in the 3.35 to 3.40V range. If you are below the barrier, the battery will basically not charge much at all, as you noted in your reply. More importantly, if you are above the barrier for long enough, even slightly, the battery will eventually get to around 90% charge without further intervention (albeit with ever-dropping current).
The key word is 'eventually'. If you set your charge target too low and the charge controller then cuts off the voltage the instant it hits that target you could easily end up with a battery that is only 20% charged.
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This is perfectly fine for a 'Float' voltage set below this value, e.g. to 3.3V for example (remember, the discharge curve is very different from the charge curve!). But it is NOT fine for a Bulk or Absorb voltage set below around 13.8V (3.45V per cell or so).
Anything below a Bulk/Absorb of 13.8V (3.45V per cell) or so is going to give you inconsistent results with a charge controller. Your Bulk/Asborb really needs to be at least 13.8V to get any sort of consistent charge percentage on the battery. The reason is as stated above... its because you aren't holding the voltage there. The charge controller is immediately dropping the voltage once it hits that target.
You can dial-in your Bulk/Absorp voltage. Between 13.8V (unknown but usually at least 50% charged) and 14.6V (95%+).
13.8V (3.45V/cell) - usually at least 50% but wiggles around a lot. (charge to target voltage and then stop).
14.0V (3.5V/cell) - usually around 70% charged. (charge to target voltage and then stop).
14.2V (3.55V/cell) - usually around 80% charged. (charge to target voltage and then stop).
14.4V (3.6V/cell) - usually around 90% charged. (charge to target voltage and then stop).
To get to 100% charge requires holding a charging-level of voltage (typically 13.6V or higher) for a period of time before ending the charge. The battery will continue to charge up to 100% or close to it. Faster with higher voltages, slower with lower voltages. Basically until the Cell stops accepting current (goes below 0.1C in current draw). With a charge controller this can be accomplished by setting the Absorption time to some value larger than 0. Of course, most people do not want to charge a lithium battery to 100%.
(And again for other readers, never set the Float voltage that the charge controller drops to above the cell's nominal voltage of 13.55V or so or you will over-charge the battery. 13.3V is still an excellent setting for Float).
This is also why, when testing, you have to start with the cell fairly significantly discharged... discharge it 50% or more. If you do not discharge the battery prior to testing, your will get a false result from your charge controller bulk charge test.
-Matt
Matt, you're saying:
"Anything below a Bulk/Absorb of 13.8V (3.45V per cell) or so is going to give you inconsistent results with a charge controller."
But if I charge to say 3.4V only and have a long absorption time, this result should be fairly accurate and repeatable. I can set the Absorption time as well as a Tail Current in the Victron to end Absorption and switch to Float. So if either the Absorption time runs out OR the current goes under the Tail Current threshold the controller switches to Float.
I've done this before and could observer that it won't take longer than ~1h (if the sun is out) to drop the current from 20A to under 1A at 3.4V CC charging. That would mean the cells have fully absorpt at this voltage of 3.4V. And I should be able to get back to this exact point with the next cycle.
@@OffGridGarageAustralia At lower target voltages, the current drops off very quickly, even before the battery gets much above 50%. At 3.40V you could easily see the current drop off to close to zero with the battery only 50-70% full (its a very wide range). If you trickle-charged it forever at 3.40V the battery would eventually get up to probably around 90% full, but the problem is that the time required is completely indeterminate.
So the issue with using 3.40V for you is that you could wind up leaving quite a bit of your solar array's power sitting on the table unused due to the current drop-off. Now the question is... how much? And the answer is I don't know because your charge-rate is already really low so you might actually be putting most of the array's power into the battery through a good chunk of the current drop-off. I just don't know the answer with regards to how much solar power you wind up wasting during the current drop-off period.
You will need to determine just how much the state-of-charge shifts around with target settings that low. My expectation is that even with the low charge rate, 3.40V/cell target could result in a battery bank that shifts around between 50% and 75% of full at the point the charge controller thinks it is done, depending on starting conditions.
I think you would probably get more deterministic results with a 3.45V/cell target. At least I, personally, would not use a target lower than that even if I were trickle-charging at an ultra-low C-rate.
The other issue still remains as well... small differences between cells will get magnified around 3.40V due to the voltage/current curve around that voltage, resulting in more out-of-balance cells. Another reason to have your charging target be at least 3.45V.
-Matt
What you are talking about is not really self-discharge. You are talking about the surface charge going away which is a product of battery internal resistance. A fully charged flooded lead-acid battery is fully charged at 12.8V and some AGM Lead Acid batteries are fully charged at 13.0V. So the float voltage for most charge controllers will be slightly above that to keep the voltage high enough to prevent sulphation while also keeping the voltage low enough to reduce water loss. Most quality lead-acid batteries will lose about 5% per month due to self-discharge. So a 280Ah FLA or AGM battery will have a self-discharge rate of about 20mA @ 12.8-13V.
When you charge most lithium chemistries they will still have a small amount of surface charge but they have lower internal resistance and also a lower self-discharge rate at about 0.5-2% per month. The self-discharge rate of your 280Ah cells will be about 2-8mA. Your lithium batteries will still draw power to match their self-discharge rate at whatever voltage you charge them to but your meter is likely not accurate enough to show the current at that rate. The reason you don't float charge your lithium batteries with the same settings as lead-acid is that the charge curves are different enough that you can use a differential instead and prevent the lithium battery from staying at a high charge state when you are trying to get the maximum number of cycles out of the cells. You typically try to cycle most lithium battery chemistries between 10% and 90% state of charge to get the maximum cycle life while also taking into account the trade-off with calendar aging.
Thanks for your great explanation.
@@bobby1970 Can you point me to a credible source that states that doing a discharge down to 10% capacity even one time will irreversibly damage the cells?
Every cell type and manufacturer generally quotes their charge cycle life at 100% DoD to 70%-80% capacity. So a typical NMC cell can do 300-1000 cycles at 100% DoD. A typical LiFePO4 cell is can do 1500-2500 cycles at 100% DoD. The only reason people stay in the middle 80% of the capacity (so between 10% and 90% SoC) is that the cycle life improves enough to hit the sweet spot between calendar aging and cycle life while still having most of the capacity. Staying between 90% and 10% SoC will generally net you 4000-6000 cycles to 80% original capacity (this varies a bit between manufacturers, batches and battery chemistries). This is 11 to 16 years of service being cycled once each day in a typical solar installation use. Most of the information available states the calendar life of LiFePO4 cells to be around 10-15 years. The point here is that these cells will degrade at a specific rate over time even if they are being stored on a shelf at a storage charge for their entire life.
@@bobby1970 : You are referring to Lead acid chemistry, NOT LiFePo4. LiFePo4 can discharge 100%.
Watching the younger kid demonstrating charge cycles, he was saying you can get beyond 10,000 cycles if you stay between 75% down to 35%. That is over 30 years. Now, I understand conditions would have to be most ideal ..like temp of the battery and ambient temps which can minimize battery life but damn.. that is j credible. Even this fellow is bulking to about 75%. For me.. with 1450 watts solar tied into my Victron 150/100 charge controller. Theoretically , I can charge back to 75% or 13.4 volts using solar, then use solar on whatever I’m discharging, unless it exceeds that 1450 watts.. then at night discharge three 300 Ah batteries to the 40-50% only to bring it back up to my set high end parameter at 13.4 volts or 75% of maximum. Right now, I am running eight 125 Trojans six volts set in four pairs. I have a residential fridge too. This winter, I’ll sell my 8 batteries.. which are in excellent shape and two years old, go to three monster lithium batteries and call it a life.
This was very helpful. Thanks for uploading! / Thumb up off course ...
Thank you very much!
I am glad I found you, here on UA-cam. I just am in the process of switching my solar system from lead acid to lithium and I am finding the charging algorithms to be completely confusing - that is, until I found your channel. Now, things are starting to make sense! Thank you for sharing your knowledge.
Very very interesting discussion on float charge. I would be very interested to see your experience with the EPEver Tracer AN. This is what I have for my Skoolie (School Bus RV conversion) and I'd love to know what to set my settings... Any advice would be welcomed!
Me too!
I have found your observations to be spot on, especially for EPEVER charge controllers, which many think are faulty, or don't work with Lithium batteries. Their default settings are way too high for LIFEPO4, and the gap between boost and float create the challenge exactly as you mentioned. Your video was the most informative and educational one I have seen, and rectified what I thought was an issue with my 3 different EPEVER Charge controllers in my off grid setup.
Thanks a lot for sharing and your kind feedback. That is great that you could understand the problem and finally fix it.
I have had a persistent problem across various models of Epever charge controllers. When battery is at a near full charge with FLA batteries or anything above ~13.x Volts on my recent LiFePo batteries the charging suddenly ‘drops out’ to only a couple amps or so. In good sun it will not recover to ‘normal’ charging until the following morning (darkness having occurred overnight) OR if I happen to be home I can turn off the panels, turn them back on, and it immediately tracks mppt and begins charging at 25, 30, 38A or whatever the sun position can muster.
This occurs and has occurred on a 3210AN, one older tracer 4210AN and a newer triron 4215AN, a 5415AN, and a 6420AN.
This does not occur /has not occurred with my MPP Solar AIO hybrid, nor with my 30A P30L PWM controller. Only the Epevers.
I was about to sell everything Epever but I am going to attempt again with 14.2 boost and float and see how it goes. Seems a bit ridiculous that these otherwise excellent mid-shelf products have not been able to work dependably. Others on forums report similar issues so I’m not alone and would love to solve this.
Any update did you fin the problem
are you controlling the EP charging parameter with the MT 50 meter? Just getting into this EP brand, setting it up next week. Hope you can respond
Best video I've seen on this topic.
yes and simple enough for a dummy like me to understand.
If you want to shorten the life of your battery follow his advice. Setting the float and absorption so close is foolish. It will cause charge microcycles and shorten the lifespan of the battery. You should really just stick with the preset settings of the victron. When the sun's out I might be getting 800 watts going. My voltage might be showing let's say 27v once a cloud rolls over it immediately drops to 26.5. this proves that the cells aren't really at 27 volts. Their actual voltage is much lower. So if I was having my absorption at 27 volts I might only be utilizing 50% of my potential capacity. I might as well just go buy some lead acid batteries if I'm going to only use 50%. What is this guy trying to leave his cells to his great-grandchildren?
@@farmerjhemp yeah we will have to wait and see 10- 15 years from now. Im not going to hold my breath lol
Hands down best explanation
Great way to explain. Thanks.
The frog sound is better than any free music used in youtube videos. :)
Chicken could bring some more rythme. :D
Excellent explanation and visual on a subject that many dont understand.💥🤘
My goodness, I actually understand this now.
Thank you.
The frog is fast becoming a star!
The frog is telling you "If you love your LiFePo4 Battery bank..Keep the Victron Controller" 🐸
Think one of his battery was croking out.
Always Victron, so much more quality, saving you money in the long run ;-)
@@HansKeesom , no doubt, Victron seems to be the best. It's one of the few charge controllers that have Bluetooth. I just got my Victron controller, and I love it, especially with all those settings that I can customize.
@@HansKeesom have you tried to call them for technical advice ? Hopeless
@@copperknob1971 Technicall support for Victron products........... what are you talking about, you don't need technicall support for Victron products once you have a basic understanding of solar systems.
Why does the battery voltage immediately drop on a lead-acid when removed from the charger? Because the resting voltage of a lead-acid is 12.7v, not 13.4v. It's not due to self-discharge (that will happen over time). The charging voltage is always higher than the resting voltage, otherwise, the battery will not charge.
True for every chemistry
what is the resting voltage for lifepo4? is it 14.0v or 13.6v?
3.6v per cell, so 14.4v for a 4s battery.
More of an issue with lead acid as there is a higher differential between charge and resting voltages.
Excellent video explaining why float shouldnt or cant be used with lithium.
You made it more clear than my battery manufacturer and solar componant supplier, both of whom did ok but not as well as you. Thanks for the effort.
Glad to see you escaped from that tiny box.
> explaining why float shouldnt or cant be used with lithium
I'd say it explains that "float" for Pb and Li means different things, and the Vfloat setpoint is used for different purposes.
Nice job! Thanks for the information. I would like to see the epever in use if possible, waiting on batttery order to upgrade my system. Thanks again! Happy New Year!
@Glen Osborne I don't think so, never saw one.
wow .... literally years of being confused and 20+ minutes clears all the fog !!!
Thank you
Now revisiting your video two years later: on my Victron the Lifepo settings are bulk 14,2V and float 13,5V. That makes perfect sense because like you said in another video the voltage from a fully charged battery drops to 13,5V after a while no matter what if you charge it with 14.2V or 13.8V (13.5 is 100% from my mfg's handbook). When the charger hits float, you must restart it to start a new cycle.
Can't wait to see the EPEver video as I have the BN series and a 120Ah Lithium Iron Phosphate battery. New Subscriber :)
Welcome aboard!
what I understand in this video is in my case. I have a motorhome then I want that my LiFePO4 stay always at 100% so, I need to configure is : absortion and float 14.2v and then I have my battery ready for the night. Is it true? thanks.... and god job!!!
YES PLEASE DO AN EPEVER VIDEO WITH USING THE EXTERNAL GUAGE/CONTROLLER.
As I read the info from Epever, the external controller cannot set Lithium
@@michaelbouckley4455 It can, but you have to set the battery profile to " user" and then input the parameters manually.
Thank you very much for addressing the setting parameters relative to the chemistry of the battery. That is the fundamental feature that need to be look at first ,before embarking on the charge/discharge of batteries.
What % of battery capacity would you recommend for long term storage? I have heard 50% a fair amount of time but, interestingly, when I talked with Battle Born they told me they recommend fully charging their batteries for long term storage. So, what is one to do?
I have an off grid cabin that is not used for months at a time and this is in a cold weather climate.
You like to keep your batteries at 80% max charge it looks like. I assume this is for longevity of the battery. Mostly I have heard about preserving battery longevity one should stay between 10 and 90% of capacity. Are you just taking extra precaution or do you have data that might reveal 20 and 80% window for discharge is actually optimal??
Thanks for this and other videos. Very informative>
I have question ...if a lithium battery has a certain number of charge cycles ..let's say 2000... would the constant "little charges" back up to maximum severely reduce your number of cycles and lessen battery life ?
Check how well the lithium battery in your cell phone works after 700 cycles or two years :)
There are good batteries and poor batteries, so battery quality will be the first criteria, however, a complete cycle is between two voltage thresholds so micro charging will have a lesser chemical effect and less degradation
When a battery lists a cycle life of 2000 cycles, it usually means you can expect the battery to survive 2000 full cycles of the battery
So if you discharge and charge it 10% a day, you complete 1 cycle in 10 days
This doesn't take into account damage from overvolting, undervolting, or discharging in the cold or heat. So long as you keep your battery in its normal voltage and temperature, little charges shouldn't significantly impact cycle life count
@@andrewallen9993 the battery in your phone is not lifepo4.
I was wondering the same thing because I know on my Milwaukee M18 5 amp battery that's rated for 1000 minimum cycles. I spoke with a representative about lithium ion or cell phone batteries and he had stated that every time you charge a battery no matter what battery it is or what kind or how large or small that count as a charging cycle because you've discharged a little bit and recharged a little bit Which is technically a charging cycle.
Well done Andy , these setting need to be correct and to be setup for each appreciation to maximise battery SOC selected , as a discharge will always be there as add components (inverters, fridge, online monitors) are consuming power at different times and condition. Cheers
I need to do more testing once the whole system is setup to confirm all this. From what I could experience so far, this seems to work the best.
Thank you for posting this, I am running a 24v hybrid system and have set the back to recharge voltage at 25.5v and the float charge at 25.1v. I have learned so much from you. Thank you again for your good work.
Re Lithium.. just turn off the float charge ... in the options list
Great video!!
I love all my victron products, alittle pricey but they seem to just work and have great software to boot.
There you are mid summer, and we are expecting a foot of snow tonight or tomorrow! Ha-ha!!
I also have the Victron MPPT and i love it. I hope this company wil make a serious balancer WITH leds AND software... smart system 👍👍👍
That would be nice indeed, I spoke with Victron about that but there are no plans for that, it would make the whole Lithium story with Victron equipment a lot easier
@@habana7638 okidoki.. yes exactly it wil make it way easyer.. it falls out of their warranty scope i guess.. too bad.
Very good company tough. Al respek. Very much thanx for the Venus open source RPI project.. I hope there is more to come. A proud 12/1600/70 owner.
You could use the absorption voltage to help the BMS balance the cells every day with solar and then float at a little higher than nominal. Since LiFePO4 has a flat voltage curve, balancing requires going closer to maximum voltage.
Also, love the frog.
If you connected all the cells to each other in parallel and maintained them for an extended period at some mid point like 3.300V, would you consider them to be perfectly balanced? Or does the nature of the chemistry result in perfectly capacity-balanced cells possibly having slightly different voltages?
Is mid balancing impractical just because of the difficulty of resolving the small voltage differences by the circuitry, or that they actually may have different voltage targets per cell?
@@wingerrrrrrrrr, they will eventually become balanced even at 3.2Vdc but it's easiest to just feed them 3.5Vdc for example until the current is more or less zero. The specsheet for these large cells do state to charge to 3.65 until 0.01C current or something and then stop charging. But, with a balancer or balancing BMS, just bringing the voltage of the series to above nominal will help the balancer do it's job because of the steeper voltage curve above nominal. If there is great imbalance, it will be hard for the balancer.
Rename this channel: off-frog-garange
Hahaha, they are here only if it rains though...
Thank you! This info worked just fine for me right here in sunny Jamaica🇯🇲
You're a life saver Andy. I just finished wiring up my DIY battery pack and solar inverter and was so confused on what to set for bulk and float charge values. There's no absorption option in my inverter and this is exactly what I needed. Its all working smooth as butter now. Thank you so much. Love from SL
Min. 1:25 , i am so confused .... ,
There is so many wrong or incomplete information in the internet .
I thought (because i have read so ) "stand-by use" is the charge voltage for batteries used in backup-systems or systems that rarely power up , but can use a lot of power on occasion.
And that "cycle-use" is for regular use , especially for heavy "machinery" like motors ...., that draw a lot of current on a regular basis ....
Min. 2:40 , i saw some youtube videos of a person that after charging and balancing LiFePo4-Batteries ...., he let them sit for 14 Days in order for the batteries to settle , or even out ....
All this things you are doing , you are taking care so much ...., like charging only to 80% in order to maximize battery life . I think you should show somebody what you are doing ...., else one day ..., maybe in 5 , 10 , or 20 years somebody is going to come and abuse your batteries ... , because he did not know how much you are taking care ... , and you did not explain to your sons or daughters ... .
I am sure you well know how much work is it to be a self-thaught learner with out a teacher ... , i think you dont want your kids to start from zero as far as solar tinkering is concerned .
Even if you tell them charge the batteries only to 80% in order to last a long time .. ,
then they would likely have to investigate again ... , how much charge or what voltage is 80% charge for LiFePo4 - Batteries ...
Mostly Datasheets dont really show this kind of things for an average person ... , if there is a datasheet at all ... (Voltage Chart)
You are correct there is (and needs to be) very little continuous float current into Li-Ion battery at a given state of charge voltage. Li-Ion cells have no safe way to dissipate excess charging. Excess charging Li-Ion cells dissipates excess charge by detrimental electro-chemical side reactions, like breaking down electrolyte which is prime cause for bloating of cells. Trick is you want a float voltage that has almost no long term current pushed into battery and gets your desired amount of capacity on battery array. If you take float to 3.65v or higher you will see some signifcant continuous current pushed to battery that is detrimental for LFP battery long term longevity.
You can go up to about 3.400v per cell and achieve an acceptably low continuous push current during float that will not be detrimental to cells. UPS continous float LFP battery systems typically set per cell float to 3.35v which gives 95% capacity capability to battery array. You have to allow some voltage tolerance margin for charger and cells balance matching which is why 3.35v is a safe number.
13.2v floating is too low for most folks as it gives you 3.300v per cell which represents an open circuit rested state of charge for LiFePO4 of close to 50% capacity. If you are comfortable living with 50% capacity available this is good for less stress on cells yielding longest longevity for cells.
wouldnt it be easier to use a battery bms
Wow. I've been using LFE for some years and just started studying settings more to understand better. After tracking a few different YT thinkers on this, your few paragraphs manage to coordinate are relate some apparent conflicting ideas on float that this video did not quite clear up for me. Thanks! Your explanation now primary in my charging notebook. I'm gonna keep bulking at 14.2 because I need capacity and floating at 13.5 which Any led me to and you help me understand. I need all the sun power running my fridge etc that I can get but don't want to abuse the cells in the meantime.
@@dantronics1682 A bms is not a substitute for charge controller parameters. It's protection against damage from extremes
I think the concept of float current as implemented by technology is to deliver float current only when the battery voltage is lower than the float voltage. This means if lifepo4 will not self-discharge below float voltage then float current will remain zero.
That is absolutely correct. LFP will stay at 3.35V naturally and charging will turn off completely at this point.
I've been struggling for 3 days with charger settings for my lithium battery. Found useless contradictory info all over the internet, until I stumbled on this video. Great advice. Looks like I have now set my charger correctly. Only if I had seen this video sooner
Same here , longer than 3 days
Thanks a lot for your kind feedback, guys! Much appreciated. I felt the same when I started, reading through endless forums and found information which did not make much sense.
The inconsistencies are astounding!
Respected sir
If you can ...please make a video that how can we get a maxmium life span of our lifepo4 battery .....
What should the dod and soc ❤❤❤
Wow, glad YT recommended your video, this cleared up a lot. Recently on a forum where people adamantly said not to float Li batteries. Even a representative from a certain inverter/charger company said Li should not be floated. As a solar newbie, I was confused by this. Looks like Float for lead and Li are two different things entirely. My battery manufacture even recommends a float voltage for their Li batteries. I set my batteries up per my manufactures recommendation including float, and all seems fine.
And what floating voltage did they recommend olvs its full capacity!?
@@tradingtechautomation693
I have 48v EG4 LP4 batteries. From their spec sheet:
Charging Voltage (Bulk/Absorb) 56.2V (+/- 0.2V)
Float 54V (+/- 0.2V)
So there not all the same it seems.Battle Borns Green Dragon says to shut off float.And bulk or absorb ,don’t remember because I can’t do it with this Jamboni mppt.Learning and will upgrade mppt.
I think keeping the same setting for bulk and float is a good way to go if you have a have some kind of load most of the time. I am not sure it would be good if you aren’t applying a load most of the time. This is something I have no clue about.
I use to think the idea of having solar was to power something and not just to charge the battery. wasnt the batteries there to fill in the gap when there is no solar?
@@dantronics1682 For me, yes. Depends on if you have loads you need to power. If not, charge up and done.
Correcto Andy la curva decreciente irá disminuyendo la corriente e intentado mantener la tensión para no sobrecargar la bateria
I have a more complex facility in a boat.
There is also a alternator and sometimes a shore charger. I understand and agree with what you said about settings in MPPT.
My problem is that when I run the engine for a while before I arrive in port, the BMS has turned off due to SOC = 100% and I have no charge at all from the solar panels. I then have to wait for SOC to go down to 95% where BMS reconnects charging.
It usually does not happen until the sun has set and I then have a starting position for the night with -10Ah, SOC = 95%
I want the alternator to charge as much as possible during the short moments I drive for the engine but still not get to SOC = 100% and BMS turned off charging.
How should I achieve that? Change the BMS or change the charge from the alternator?
Victron MPPT is set to 13.8 and 13.7V. I always have consumption in the form of refrigerators etc. so MPPT quickly restarts with BULK
If your alternator is like a modern car's you are probably sending 14.4 to 15V to the LiFePO4 battery which is the upper limit or above. Most BMS will cutoff at least14.7V I am surprised the BMS does not disconnect from overvoltage.
To force stop the charging at leas than 100% (14.4V) you must remove the cable from your alternator to the house battery and install a DC to DC charger. I use a KISAE DMT1250 and I set it at 13.4V so that's when charging from the alternator stops. I can also adjust the max. charging current in 5A incrememnts from 5-50A.
Or get the Enerdrive 40+ which is the Australian version.
Note that charging the LiFePO4 to 100% versus to only 75-80% reduces the battery's lifespan by almost half. 20%-80% SOC is the sweet spot.
@@judgedredd8876 Now days i have two DC/DC parallell. And BMS i set in ”critical mode” wich means it not turning of at SOC=100% as it used to do. Now it only turn off att critical states. DC/DC is tuned so all work well.
@@judgedredd8876LFP has such good cycle life even at full cycle charge/discharge. For some, it's worth it to get 25% more capacity for 2500 cycles than have insufficient power but battery lasts 5000 cycles. Depends on usage, space etc.
Can someone tell me if a charge controller that will work for a lithium-ion (not LiFePo4) 36v nominal? I don't mind if it's mppt or pwm. The battery is 21Ah.
The Victron MPPTs can be set to 36V systems.
off-grid-garage.com/solar-charge-controller/
Thank you and god bless
Video very helpful Thanks
Thanks a lot, John!
Perfect demonstration. I've been using the same method for 3 years.
is it ok if my mppt parameters is 13.8v Boost and 14v Float? is this fine?
Well done Andy on explaining the differences using practical demonstrations. This stuff needs to be right otherwise people will wreck their solar/battery gear.
I am working on this exact issue with my new Victron SCC. Your theory is perfect for a constant user of all available sun power…. One just needs to decide how high you want to keep it charged and then what voltage numbers to plug in so as to not waste the sunshine.. It would seem one would not not need a tail current enabled ( ? ) … or perhaps very low (1 amp) .. you didn’t state that …what do you say on the tail current if your ending abs at the same value of float.? "………BTW Great vid ,thanks..
Hi Andy, wish I had came across your video earlier. I just finished my first campervan power distribution build and found out during testing the cheaper BCDC charges all have the same issue you have explained in your video e.g no float charge. Therefore losing the top part of your battery capacity. Not a major issue but definitely something ill take into consideration for future builds. Thanks for taking the time to explain everything, I will definitely be looking at buying a more expensive BCDC charger for future builds with a float charge / setting as to primarily cover the connected loads when charging power is available.
I have an Axpert King 5kw and upgraded to a Dyness Li batt. The float phase causes flickering of some devices like the fridge light or downlights. Unfortunately the software of the Axpert is crap compared to Victron. So i simply manually switch off the power supply to inhibit float. If anyone knows the settings for Axpert King to stop float I would be glad to hear it. Finally the comms between Axpert King and Dyness doesn't work and Axpert website has no software upgrade; so the comment below is correct. btw for the frog problem i suggest a French chef.🤓
Update: the same guys that installed my 5kw Dyness came back to add another 5kw dyness in series, this time for the Axpert I had the pdf for the model with ALL the settings as the installer reconfigured the Axpert...he commented: "...wow, that is the full set of config items". Axpert working fine now. No flicker! So, it was a configuration issue. This cheapo Chinese made inveter and MPPT charge controller is working like a charm with 10kw of storage and the puniest 5 PV panels from 15 yrs ago producing 1kw at peak of Summers day. All water heating is solar....been off grid for a weeke and a half as an experiment including running the pool pump for hour a day.
Very happy to see you got a Victron controller for your main battery bank. Its a quality piece of equipment that actually works like it should. Keep those beautiful cells safe, so you get many years of use. Love watching you test all the different electronics and cells. Looking forward to seeing everything set up and also looking forward to the solar gate project. Good luck!
Thanks a lot. It is very exciting for me to test all this equipment and see what works and what does not so much.
@@OffGridGarageAustralia Testing is also my favorite part of the build. It just so much fun trying different configurations and figuring out the best combination for your needs. It makes for great content as well. Looking forward to the next videos.
I didn't understand why it was bad to set to 13.2V. If 13.4V, you said you're at 95% SoC, but I thought you wanted to max your LFP to 80%.
Well, it is not possible to use just the voltage to charge to a certain SOC.
In later future, we have found the information on how to charge these cells correctly.
For lithium you use the same voltage in all parameters bulk absorption and floating 👍🏻👍🏻👍🏻👍🏻
This does not work with all controllers though I think. I'll try it out...
That is correct. LiFePO4 cells are full at 3.65 volts. 3.65x4=14.6 volts. It is absolutely OK to hold the charger at that voltage indefinitely. The current the battery will take at that voltage declines to almost exactly 0 amps. But if the charger backs off to 13.4 or so, that's OK too. The battery will lose almost no charge, and if it does drift down (which might take months) it will still be at ~98% full.
@@jimmurphy5355 "It is absolutely OK to hold the charger at that voltage indefinitely." - This is not the case. A LiFePO4 battery kept at full charge all the time will sustain damage. Furthermore, when the battery is full you must disconnect the charger, because the battery voltage will then settle to around 3.5V - keeping it at 3.65 will cause damage, and you can actually overcharge. There are several resources you can find, e.g. from Nordkyn Design that show this. Normally you stop charging when the charge current reaches 5% to 10% of the Ah rating of the battery - if you cannot stop absorb based on current, you'd pick e.g. two hours, but then disconnect.
@@upnorthandpersonal Well, the battery I built is charged up by my solar charge controller to 3.65 volts per cell every day. And it holds there for a few hours until I use the battery in the evening. My usage runs it down to about 20-23% most days. The coulomb meter the monitors the charge has not shown any detectable reduction in capacity after the first 300 cycles. There was about a 2% reduction capacity in the first couple week, but nothing I can detect after that.
@@jimmurphy5355 Holding it for a few hours and then cycling it back down to 20% daily is fine. Keeping it at 100% (or near) state of charge for prolonged periods of time is not. It's the same reason why for long term storage (months) you store LiFePO4 at ~50% state of charge. Even though I would still recommend not holding it at 3.65 for too long (normally based on current flow dropping to 5% to 10% of the Ah rating) for best cell cycle life.