I don't see why not. Just keep in mind that the two batteries will have different BMS's. They could possibly have different settings for low voltage and high amperage shutoff. If you keep the bank between 10% and 90% most of the time you will be just fine! Thanks for the comment.
You can use different amp hour capacity batteries together, the problem is when you are discharging them in parallel. Each batteries different amp hours will kick off the lower amp hour batteries when the BMS turns off on your lower amp hour batteries. And that can cause strain on your other higher amp hour batteries. Also when you charge all your batteries together it can get out of balance on all your different battery cells. Best to keep batteries same amp hour rating and voltages together. They will balance better and drain better without their BMS turning them off.
Interesting experiment. I suspect the voltage differences and the varying amp push/draw might be due to each pack having cells made by different manufacturers, that there may be some variances in those that affected how they took in charge and their voltages, and how their voltages dropped when taken off charge. Might also be some differences with the BMSs causing some unexpected variances as well.
@@OffGridBasement Ah yeah! The wiring inside might make a little difference too, didn't even think about that. I find all these videos I've found on this topic lately to be great - everything I'd read up to this point has been "no no, can't parallel different capacity packs, don't do it!" and... well...
This was a cool series of videos. Thank you for sharing. I've been too scared to try this due to the long-time warning of keeping safe size and brand of battery.
Exactly what I wanted to see. It proves that all batteries will eventually charge completely. Also the gauge of wire isn’t a factor since during the final charging there is such a low current.
I'm glad you got something out of it. As long as you split the wiring from a busbar to each battery you just need to calculate the max amps divided by the number of batteries. Wiring and breaker from the busbar to the inverter needs to be sized to the output of the inverter. Thanks for the comment.
Guys that fly FPV often charge different amperage lipo batteries with a parallel board all the time. However using lifpo4 with bms can be scary on drawing high amperage out. RV draw OK, but larger draw like cabin or house you are asking for trouble.
You need to leave the charger connected for 30 minutes per 100 Ah of capacity. This will give the BMS time to balance the cells, this is the absorption cycle. You will notice during this time a small charge going to the battery. If this is not done the cells will soon be imbalanced affecting performance. Once absorption finishes they should be close to 14.2 volts.
The length of the cables must be the same to have a perfectly balanced system, and I doubt that dissimilar batteries can ever be balanced. I would expect differences in charging and discharging between them which would likely cause some to fail sooner than others. I like your experiments!
What you find very strange at 6:45 I found to be completely expected. You connected the cells together when they were somewhere down the SOC curve but there is no way to know where each is because the curve is so flat. The 100Ah was obviously at a lower SOC when connected and it doesn't really matter how long they are connected, they will not get close until you take them to near 100%SOC. I would also say that your wires are too small and all the same gauge. You would be better off by connecting paralleling wires between the three + and three -. I connect my paralleled batteries with 4/0 cables so that they are all at the exact same voltage. Your system was always going to have different voltages on each of the batteries and that is not really parallel. To be parallel, all batteries must be at the exact same voltage and that is only done by having interconnecting wires big enough to not produce voltage drops to each battery. As for your tester. Those usually have less than 180w for the max draw. You said that your three batteries have a total capacity of 425Ah so at a nominal voltage of 12.6v that comes to 12.6v x 4250Ah = 5,355W. at 180w discharge max that will come to about 30 hours for the test.
I'd never have considered charging different amperage batteries in parallel, like this. Theoretically it should be fine! They all have Control Modules, which should be fine, "theoretically". I think you have just provided evidence it works in practicle application. So long as all the batteries together do not draw more current than the charger provides. I thinnk, Right? The question is, how do they survive long term in such an configuration. Also, would the results be the same (or similar) using a solar array? Good test.
Thank you. This setup does work in practice, but I'm unsure about how it would work in the long run as well. I plan on continuing with the setup for a while to see the long term effects of battery balancing. I really don't know how the setup would react to a solar charge controller. The fluctuation of the amperage might really mess things up, but I'm not ready to test that yet. Thanks for the comment.
Yo need to use atleast 8 awg gauge wires. Keep in mind you need to use fuses that are rated a little higher than your amp hour battery. So if you have a 50ah battery then you can use a 70 amp fuse, if you want to be safe you can use minimum 50 amp fuse. But fuses need a little leeway for amp draw. You use 12 awg gauge wire for anything lower than 30 amps. Any amp loads that are higher, such as your lifepo4 battery, use higher amp fuses and lower gauge wire.
I bought it from Amazon. Here is the description and link. Ardroit 14.6V 30A LifePO4 Battery Charger Trickle Charger Smart Charger and Maintainer for 12V LiFePO4 Lithium-Iron Deep Cycle Rechargeable Batteries & Battery Desulfator amzn.to/3gznwFg
I'm thinking that you are going to be limited by the battery with the lowest "full charge" voltage. With that battery, if you charge it to more than that, it is going to drop down to that once you disconnect it from the charger. The battery with the higher "full charge" voltage will then be charging the lower voltage battery, but the lower voltage battery will not stay at that level, thus the charge is wasted. This will continue until the higher "full charge" battery is at the same level as the lower "full charge" battery. Another way to visualize this would be like water flowing into tanks... Let's say you have two open top tanks, each 13.7" tall, but one of them being 10" wide and the other being only 5" wide. Let's also says that you have a water supply hooked up to both that will allow you to fill each up to the 13.7" level. Let's also run a small diameter line interconnecting the bottom of the two tanks so that they seek equilibrium. And lastly, let's add a small overflow hole near the top of each tank -- at the 12.5" level on the smaller tank and at the 13.4" level on the larger tank. These overflow holes might not even be the same diameter which would thus simulate different discharge rates. You fill the two tanks up to 13.7" which causes the water supply to be shut off. At this point, but tanks are leaking water out the overflow holes. The larger tank is going to get to it's overflow level and the water will stop coming out of it. If the smaller tank has not reached this level yet, then it will continue until it reaches the level of its overflow hole. But since the two tanks are connected and the smaller tank has a lower overflow hole, the water from the larger tank is going to flow into the smaller tank through the interconnect line. This will raise the level of water in the smaller tank above the overflow hole which will cause the water to go out it. This is going to continue until the larger tank is at the same level as the smaller tank. With a battery bank, this energy has go go *somewhere* and it is most likely dissipated as heat due to that whole "Conservation of Energy" thing that we *should* remember from high school Physics class...
I had a lot of questions on this on the subject of hooking up batteries with different mah but same volts in parallel. I have about 15 18650 batteries all with different mah and few have no label to know the mah of the battery, so I was wondering what would happen if I hook them all up, but I think your video has shed more light on that (i.e they all even out) And while charging, it all depends on how dumb your charger is to not figure out that one of the batteries is fully charged. Am About moving to the part three. please can u make a video to show an EASY way to check the mah of batteries
I'm happy the video helped shed some light on the subject. Once all the batteries are in parallel you can't really find the mah of individual cells if they are different capacity. Sorry I can't give you more information.
Late to the party, but this video is saying that you can mix different types of lithium batteries on a charging block. I want to know if I can mix a couple of different 100ah lithium batteries on my camper? I bought a camper a few months ago and it has one 100ah battery and I would like to add a 200ah battery in my battery box so that I have 300ah. Will it safely charge both batteries off of the solar?
Yes. It's totally safe. Keeping the batteries wired in parallel is fine with different capacities. Just set your charge controller to charge up to 14v. If you plan on it discharging all the way to zero, then you might have an issue with one battery shutting off before the other. Hope this helps. Thanks for the question and comment.
Yes. They all charged up to 14.16v. I thought that was odd since I was using a lifepo4 charger that is rated for up to 14.6v. Anything over 14v is fully charged though.
@@OffGridBasement So in your opinion how important is it that the batteries are all the same. Seems to me that very different batteries sizes eventually balanced out. Or is it more important that the battery chemistries are the same? I see a lot of people harp on about the important of getting the same batteries in one bank.
@@thebugs4934 my opinion is if you are using your system with heavy loads or you cycle it multiple times a day then you should have all the same battery. The resistance in the cells will be closer to the same and the settings in the BMS are identical.
Hmmm interesting. Another test will be w a load and charger. And then solar w the different batteries and mppt. I’ve always tried to use same battery models in systems out of paranoia of balancing over many cycles and loads of battery w heaters as we operate off grid in them wild. Will be interesting to see your tests
voltage does not tell the full story on lifepo, top balance them together is a good idea, still, it will work no probleme, i do that with my battery bank, one is 24v 280, the other is 230 and the last one is 130 amp, no probleme for month .
It's really all about learning how to get the most of what you have. This setup has helped more than once to charge my other systems. Thanks for the comment.
Very interesting, just like being in science class. Well done.
Glad you enjoyed it! Thanks for the comment.
Excellent, your experiments tell all, thank you!
Thank you and thanks for the comment!
That's incredible!
You answered my question of have same voltage batteries with different storage capacities. Thank you
Glad I could help! Thanks for the comment.
good show , i might add another batt from other brand to my kit now
I don't see why not. Just keep in mind that the two batteries will have different BMS's. They could possibly have different settings for low voltage and high amperage shutoff. If you keep the bank between 10% and 90% most of the time you will be just fine! Thanks for the comment.
Thanks. Interesting. I was thinking about adding to my small cabin system. Looking forward for the journey. Thanks again.
Hope this helps in some way. Thanks for the comment!
You can use different amp hour capacity batteries together, the problem is when you are discharging them in parallel. Each batteries different amp hours will kick off the lower amp hour batteries when the BMS turns off on your lower amp hour batteries. And that can cause strain on your other higher amp hour batteries. Also when you charge all your batteries together it can get out of balance on all your different battery cells. Best to keep batteries same amp hour rating and voltages together. They will balance better and drain better without their BMS turning them off.
This is true. Thank you for the info. This was only meant for proof of concept.
Awesome vid many thanx from aus.
Glad you enjoyed it! Thanks for the comment.
That was interesting how the charge fluctuated to get each battery fully charged. It's good none of them received too much!
I was actually hope for more charge to each battery, but I don't want to damage anything quite yet!
Interesting experiment. I suspect the voltage differences and the varying amp push/draw might be due to each pack having cells made by different manufacturers, that there may be some variances in those that affected how they took in charge and their voltages, and how their voltages dropped when taken off charge. Might also be some differences with the BMSs causing some unexpected variances as well.
Yes. All of that is true. Internal resistance also plays a big part. Thank you for the comment.
@@OffGridBasement Ah yeah! The wiring inside might make a little difference too, didn't even think about that.
I find all these videos I've found on this topic lately to be great - everything I'd read up to this point has been "no no, can't parallel different capacity packs, don't do it!" and... well...
This was a cool series of videos. Thank you for sharing. I've been too scared to try this due to the long-time warning of keeping safe size and brand of battery.
I'm glad you got something out of it. Everything is still working fine for my setup. Thanks for the comment.
Exactly what I wanted to see. It proves that all batteries will eventually charge completely. Also the gauge of wire isn’t a factor since during the final charging there is such a low current.
I'm glad you got something out of it. As long as you split the wiring from a busbar to each battery you just need to calculate the max amps divided by the number of batteries. Wiring and breaker from the busbar to the inverter needs to be sized to the output of the inverter. Thanks for the comment.
Guys that fly FPV often
charge different amperage lipo batteries with a parallel board all the time. However using lifpo4 with bms can be scary on drawing high amperage out. RV draw OK, but larger draw like cabin or house you are asking for trouble.
You need to leave the charger connected for 30 minutes per 100 Ah of capacity. This will give the BMS time to balance the cells, this is the absorption cycle. You will notice during this time a small charge going to the battery. If this is not done the cells will soon be imbalanced affecting performance. Once absorption finishes they should be close to 14.2 volts.
Thanks for the info and the comment.
The length of the cables must be the same to have a perfectly balanced system, and I doubt that dissimilar batteries can ever be balanced. I would expect differences in charging and discharging between them which would likely cause some to fail sooner than others. I like your experiments!
Thanks for the comment and info.
What you find very strange at 6:45 I found to be completely expected. You connected the cells together when they were somewhere down the SOC curve but there is no way to know where each is because the curve is so flat. The 100Ah was obviously at a lower SOC when connected and it doesn't really matter how long they are connected, they will not get close until you take them to near 100%SOC. I would also say that your wires are too small and all the same gauge. You would be better off by connecting paralleling wires between the three + and three -. I connect my paralleled batteries with 4/0 cables so that they are all at the exact same voltage. Your system was always going to have different voltages on each of the batteries and that is not really parallel. To be parallel, all batteries must be at the exact same voltage and that is only done by having interconnecting wires big enough to not produce voltage drops to each battery.
As for your tester. Those usually have less than 180w for the max draw. You said that your three batteries have a total capacity of 425Ah so at a nominal voltage of 12.6v that comes to 12.6v x 4250Ah = 5,355W. at 180w discharge max that will come to about 30 hours for the test.
Thank you for all the great information! I really appreciate it.
I'd never have considered charging different amperage batteries in parallel, like this. Theoretically it should be fine! They all have Control Modules, which should be fine, "theoretically".
I think you have just provided evidence it works in practicle application. So long as all the batteries together do not draw more current than the charger provides. I thinnk, Right?
The question is, how do they survive long term in such an configuration.
Also, would the results be the same (or similar) using a solar array?
Good test.
Thank you. This setup does work in practice, but I'm unsure about how it would work in the long run as well. I plan on continuing with the setup for a while to see the long term effects of battery balancing. I really don't know how the setup would react to a solar charge controller. The fluctuation of the amperage might really mess things up, but I'm not ready to test that yet. Thanks for the comment.
Yo need to use atleast 8 awg gauge wires. Keep in mind you need to use fuses that are rated a little higher than your amp hour battery. So if you have a 50ah battery then you can use a 70 amp fuse, if you want to be safe you can use minimum 50 amp fuse. But fuses need a little leeway for amp draw. You use 12 awg gauge wire for anything lower than 30 amps. Any amp loads that are higher, such as your lifepo4 battery, use higher amp fuses and lower gauge wire.
Thank you for the information and the comment.
No you don't, shows how much you know. Most chargers that can charge up to 50ah comes with 2.5 - 4mm cables.
Really great video, Can you show me your charger and where to buy it ?
I bought it from Amazon. Here is the description and link.
Ardroit 14.6V 30A LifePO4 Battery Charger Trickle Charger Smart Charger and Maintainer for 12V LiFePO4 Lithium-Iron Deep Cycle Rechargeable Batteries & Battery Desulfator
amzn.to/3gznwFg
I'm thinking that you are going to be limited by the battery with the lowest "full charge" voltage. With that battery, if you charge it to more than that, it is going to drop down to that once you disconnect it from the charger. The battery with the higher "full charge" voltage will then be charging the lower voltage battery, but the lower voltage battery will not stay at that level, thus the charge is wasted. This will continue until the higher "full charge" battery is at the same level as the lower "full charge" battery.
Another way to visualize this would be like water flowing into tanks... Let's say you have two open top tanks, each 13.7" tall, but one of them being 10" wide and the other being only 5" wide. Let's also says that you have a water supply hooked up to both that will allow you to fill each up to the 13.7" level. Let's also run a small diameter line interconnecting the bottom of the two tanks so that they seek equilibrium. And lastly, let's add a small overflow hole near the top of each tank -- at the 12.5" level on the smaller tank and at the 13.4" level on the larger tank. These overflow holes might not even be the same diameter which would thus simulate different discharge rates. You fill the two tanks up to 13.7" which causes the water supply to be shut off. At this point, but tanks are leaking water out the overflow holes. The larger tank is going to get to it's overflow level and the water will stop coming out of it. If the smaller tank has not reached this level yet, then it will continue until it reaches the level of its overflow hole. But since the two tanks are connected and the smaller tank has a lower overflow hole, the water from the larger tank is going to flow into the smaller tank through the interconnect line. This will raise the level of water in the smaller tank above the overflow hole which will cause the water to go out it. This is going to continue until the larger tank is at the same level as the smaller tank.
With a battery bank, this energy has go go *somewhere* and it is most likely dissipated as heat due to that whole "Conservation of Energy" thing that we *should* remember from high school Physics class...
Thank you for the great analogy and comment.
thank you very much for this video i like it...
You are most welcome. Thanks for the comment.
I had a lot of questions on this on the subject of hooking up batteries with different mah but same volts in parallel. I have about 15 18650 batteries all with different mah and few have no label to know the mah of the battery, so I was wondering what would happen if I hook them all up, but I think your video has shed more light on that (i.e they all even out) And while charging, it all depends on how dumb your charger is to not figure out that one of the batteries is fully charged. Am About moving to the part three. please can u make a video to show an EASY way to check the mah of batteries
I'm happy the video helped shed some light on the subject. Once all the batteries are in parallel you can't really find the mah of individual cells if they are different capacity. Sorry I can't give you more information.
Late to the party,
but this video is saying that you can mix different types of lithium batteries on a charging block. I want to know if I can mix a couple of different 100ah lithium batteries on my camper? I bought a camper a few months ago and it has one 100ah battery and I would like to add a 200ah battery in my battery box so that I have 300ah. Will it safely charge both batteries off of the solar?
Yes. It's totally safe. Keeping the batteries wired in parallel is fine with different capacities. Just set your charge controller to charge up to 14v. If you plan on it discharging all the way to zero, then you might have an issue with one battery shutting off before the other. Hope this helps. Thanks for the question and comment.
@@OffGridBasement Hello sir, wouldn't 14v be way to low to fully charge lithium?
It would give you 99% charge. You would be at the upper elbow of the charge curve.
Hellow sir, can i parallel the lifepo4 32650 ang gel type batteries? 120ah lifepo4 and 50ah gel type batteries?
Yes you can, but I wouldn't recommend it. The charge and discharge curves are different.
Great Video. 👍
Thanks! 👍
So in the end they balanced themselves out?
Yes. They all charged up to 14.16v. I thought that was odd since I was using a lifepo4 charger that is rated for up to 14.6v. Anything over 14v is fully charged though.
@@OffGridBasement So in your opinion how important is it that the batteries are all the same. Seems to me that very different batteries sizes eventually balanced out. Or is it more important that the battery chemistries are the same? I see a lot of people harp on about the important of getting the same batteries in one bank.
@@thebugs4934 my opinion is if you are using your system with heavy loads or you cycle it multiple times a day then you should have all the same battery. The resistance in the cells will be closer to the same and the settings in the BMS are identical.
@@OffGridBasement good to know, thank you!
Thnks now i know🙌🏻
Happy to help. Thanks for the comment.
Hmmm interesting. Another test will be w a load and charger. And then solar w the different batteries and mppt.
I’ve always tried to use same battery models in systems out of paranoia of balancing over many cycles and loads of battery w heaters as we operate off grid in them wild.
Will be interesting to see your tests
I plan on doing a discharge test then connecting a 12v inverter to power a 24v charger. I'm interested in the massive losses I will get!
Now do 2 lead acid and 2 lithium and make a 48v and see how that goes.
that wouldn't be the best idea... Way different voltage curves. and in series!? No thanks. :-)
Settings wheel--->Playback Speed--->1.25
Hahaha!
voltage does not tell the full story on lifepo, top balance them together is a good idea, still, it will work no probleme, i do that with my battery bank, one is 24v 280, the other is 230 and the last one is 130 amp, no probleme for month .
Thanks for the info and the comment.
Wish I had this much time to waste...
It's really all about learning how to get the most of what you have. This setup has helped more than once to charge my other systems. Thanks for the comment.
You probably waste that much time watching youtube videos and complaining about how much time you wish you had to waste