How To Connect and Setup the BMS on LiFePO4 | Sailing Wisdom
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- Опубліковано 3 жов 2024
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BMS stands for Battery Management System and is a critical component in building a safe and reliable LiFePO4 battery. This video will teach you how to connect the BMS and how to program it. This video is part of a series:
▸ Building a LiFePO4 Battery: • How to build a Waterpr...
▸ Top Balancing Video: • Top Balancing a Lithiu...
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Good job. Looks like that crimper has seen better days though..😅
Thanks you're videos has a lot of information.
👍
Great job on all this stuff. I've been told though that the charge under temp should be somewhere between 3Ç and 5C. The reason I was told was that a portion of the battery away from the temperature sensor might be below freezing. Additionally the cells themselves can't take the rated C rate for charging near freezing temps. Low C rates I hear can be charged below freezing, but why take the chance. My JK BMS has an integrated heater port where I have silicon mats inside the wooden case. On my older batter sets I used a device to trigger the pads.
Great job, Herby! Thanks. 👍👍👍
Seems a whole lot better than the dahlgren BMS I used a couple years ago when i built the cells on our bus.
Your to good at this! Ya know what i mean!❤ Are y'all going to the boat show and bring Jr.?
This is brilliant
I still have to make my battery, but one important detail that I have read/seen somewhere else is that is very important that the cables are exactly the the same length (positive to positive and negative to negative respectively, because the cable itself has a resistance) and to not make loops with them (to prevent it heating anything metalic inside le loop, like in a induction forge).
That’s a good point. The amperage flowing through them will generate quite the magnetic field!
Do yourself a favor and search for “off grid garage”. You’ll get much better information from that channel about lifepo4.
@@RiggingDoctorwhat gauge cables are on the bms?
Indeed, this also becomes critical on long runs for the cable. Voltage drops and increased amp passing through can compound issues. For short runs like these, being similar in length is good enough.
Nicely done video. I'm not quite following what determines Most, and Least negative/positive. I follow how the series connections step up the voltage, but the most vs least is confusing. Also, would conductive loctite make sense on the internal blot threads, seems like heating and cooling might cause the to loosen. Really informative series.
When you follow the series from start to finish, the negative and positive ends of the series is the most positive and negative.
-/+.-/+.-/+.-/+
↑most neg ↑most positive
Good point about the heat cycles and the threads. I haven’t seen or heard of an issue, but I’m sure it wouldn’t hurt to do on future builds!
Ok so it’s the only negative terminal not connected and the only positive terminal not connected to another battery. Makes perfect sense.
Such an educational video detailed explained ,dear friend I I have bought lifepo4 batteries four of them 3.2v 300Amps and I'm going to connect them as 12volts what BMS do I need? Is a BMS 300amps important ? Or it depends on how much power the batteries will be charged from solar panels thank you
The 300amp BMS would only be necessary if you are going to be drawing 300amps from the battery in an instant. If you draw only 100amps for 3 hours, you would still draw the 300amp hours from the batteries but never reached the current of 300a.
Figure out what your peak load would be and then size the BMS to be able to support that load. Most house loads on a boat won’t exceed 30a total, so a 100a BMS will be more than sufficient.
Thank you for the fast response,most appreciated
Nice descriptor of these type of serial (internal) BMS-“just an interruptor switch.” This is one reason these are not well suited for alternator charging: when they are full, or detect a fault-they stop charging without warning and the alternator fries. (Wanted to say “explodes” but it really is just releasing the magic smoke😂)
How do you feel about some of your busbars not being flush onto the posts/pads? You could easily solve this by putting the “serial” busbars on top of the “parallel” busbars. You might try a thermal heat camera to monitor the heat distribution around the posts under heavy load.
You don’t mention, but what is the number of paralleled 12v batteries with this BMS? How about number of serial connected batteries? (Number of batteries with BMSs, not cells)
What was the purpose of the switch you chose not to use or install?
I do not really know, which is part of why I don’t mess with it.
It is the “remote switch” which I believe let’s you turn the BMS on or off, but you are able to perform that task via the app, hence why I don’t bother with it.
This 2p4s setup is rated at 200ah right? Bms is 120a. Meaning it can charge and discharge at a rate of 120a. Correct?
That is correct. It can charge or discharge at 120a but it holds 200ah. At full speed, it would take a little under 2 hours to fully drain or charge the battery pack.
I would always suggest to work with isolated tools and to cover the metal connectors (Sorry, i´m not a native speaker/writer)
You have it on 3.55v and 28.4v? Thats correct? I want to fix and my bms
That is correct
Thanks for the useful info. What’s your opinion on putting an AGM battery for engine starter with a DC-to-DC charger for house lithium battery? As opposed to going all lithium.
That is an option since starting can chug the amps. The dc-dc converter will keep the starter battery charged up.
I would suggest turning the converter in selectively so that the AGM doesn’t drain the lithiums down as it discharges naturally. The AGM will be full charge at a lower voltage than the lithium so make sure the dc-dc converter is set to the right voltages to keep both happy.
Basically, the AGM is a capacitor to start the motor and the boat runs on lithium.
To be fully lithium, you will need a massive bank so that it can supply the huge load to start the motor.
AGM / lithium is a much easier setup to start with.
@@RiggingDoctor Actually the dc-to-dc charger is for charging the house lithium from starter AGM. It turns on only when alternator is running. Apparently this is needed so lithium doesn’t kill the alternator by demanding too much current. Then, like you said, the AGM is needed to handle the demand by engine starting, which protects the lithium bank.
However, sailboats typically have a relatively small inboard which needs ~400 CCA. You can even buy little hand held starter lithium batteries for starting engines. I thought a sizable bank ~200Ah could handle starts, and protecting alternator without AGM is another question.
I have 912AH 12v of lifepo4. I also have an AGM starter battery. My externally regulated alternator (100 amp) charges my Lifepo4 bank and a dc to dc Victron charger that charges the starter battery from the lifepo4 bank. I also added a switch at the helm so I can turn on and off the alternator if I need it or not.
@@ericblackburn9829 my understanding is your setup has a risk that if the lifepo4 battery mostly discharged and engine is running at low rpms (under powering alternator) this puts a strain on alternator that can burn it out. Maybe you never put it under this strain or maybe your bms or alternator has built in protection. Something to consider.
@@airgapmachinethat’s why my alternator has an external regulator. It’s a balmar mc-614. It throttles down the alternator before it overheats. No problem. With this setup you get the most out of your alternator. With a dc to dc you’re limited to the dc to dc output. I have a 100 amp alternator. If I use a 30 amp dc to dc charger I’ll only get 30 amps in to my giant Lifepo4 bank. With my setup I get around 60-80 amps depending on ambient temperature. I’m thinking about adding a blower to pull the hot air away from the alternator to see if I can get a bit more.
Hi Rigging Doctor(s), I live on a small (25ft) boat and am going to be moving to Maryland next year. I need a cheap residential address, so I'm looking for the cheapest possible mooring rental (no marina amenities, just the mooring ball and address). Do you all have any advice about where/how I should look for that in MD, and do you know what the usual rental requirements are (e.g., is liability insurance usually required)? Thanks
I always lived aboard in marinas so I’m not familiar with where you can live and get an address with a ball, but I have seen a good sized mooring field near Hartge Marina (spelling?) in the West River. The marina has liveaboards so if the balls belong to them, that would be a good option.
Alternatively, you are allowed to have up to 3 mooring balls in Maryland for free. I don’t know if this would satisfy the address requirement though. Would a PO Box suffice?
@@RiggingDoctor Thanks for the recommendation. Unfortunately, due to the federal Patriot Act and Know Your Customer (KYC) laws, investment banks, the MVA, and similar places don't allow one to use PO Boxes or commercial PMBs (e.g., at the UPS Store or Anytime Mailbox) as one's residential address, because one can't live in a mailbox. There are a few boating and RV-friendly states (FL, SD, and TX) that have campground mail forwarding companies (e.g., Escapees) that do qualify as residential addresses, but I'm poor and can't afford health insurance in those states (because they're conservative-majority states that haven't expanded Medicaid to the general population). No liberal-majority states in the US, as far as I know, have campground mailbox companies -- hence, my search for a cheap mooring with an address. I've seen people in California do this (e.g., see the Sailing Emerald Steel channel on UA-cam), but I need to stay on the East Coast for family reasons. Marinas often don't have very informative websites, so I guess I'll have to call around.
The Overkill 120Amp 4s BMS has been out of Stock for ages. What's the deal?
What do you mean? That’s my favorite BMS 😭
Looks like overkill is going to have a replacement soon
@@RiggingDoctor hope so
Temperature sensor should be in the middle of the pack, because thermal runaway starts here.
Very good point!
how much can we save by building a 200 aH LiFePO4 battery by ourselves?
About $800 for 200ah.
They cost about $1000 for 100ah, so $2000 for store bought.
The materials cost $2400 for 2x200ah, so $1200 for each 200ah battery.
@@RiggingDoctor thanks!
Umm, I think the battery is 200AH but when you were setting the maximum discharge rate I got that you said you were setting it to 1C at 100A. I am thinking that 200A would be wrong as well because you derated the battery slightly less than 200AH further up. (Its hard to keep all these numbers straight in my head so maybe I misheard) However, you had switched to battery1 so maybe it is only 100AH? (that doesn't make sense if they are a pair) Or you had purposely set battery1 to discharge only to 0.5C and said 1C by mistake. That would of course mean that max charge was 0.35C or so.... 0.5C discharge would be perfectly valid for most house systems (200amps from two batteries of 400AH total). Maybe perfectly valid for motor use too as I can't think of many people who want to motor no more than 2 hours max. Anyway, it was still quite well laid out and I found it helpful. We are currently running LA but will be switching lifepo4 when these wear out.
I misspoke, good catch.
The battery is 200ah and discharging at 100amps is only 0.5C, with both in parallel they will be working at 0.25C so these batteries will have a cakewalk of a life :)
😀👍👍👍❤
Overkill solar is far from the best bms. Why don’t you talk about balancing current? In my opinion the muller bms with 5amp active balancing from muller energy is the best bms. It’s good when the cells are new and fairly balanced and great when the cells get a little older and begin to drift during heavy deep discharge. Most any bms looks great in the beginning when the cells’ internal resistance is similar. But over time, the typical 1 mA passive balancing is just not enough. Ask me how I know after years of owning Daly, JBD, and yes overkill solar bms’s.
I like how their safety features really work. To me that is the most important part! Setting up the battery pack properly then circumvents any downsides that it may have in the balancing department.
You’ll see in a few years as your cells degrade. Your balancer will not overcome the imbalance caused by uneven cell degradation and you will inevitably enter the world of active balancers. When that day comes, reach out and I’ll help you.
@@ericblackburn9829 I have had my Lifepo4 bank on my boat for almost ten years with no active balancing. they are still within .06 volts of each other
Again with the fire threats. Cya
Filmed them all at once, there’s one more after this 🫠
Fire: ua-cam.com/video/07BS6QY3wI8/v-deo.htmlsi=iCobW7jdAmJFPmmv