Discharging Lifepo4 batteries of different brands and sizes! Extreme Parallel Part 3! 

Sounds great! Thanks for the comment.

I'm glad you got something from the video. Thanks for the comment!

Glad you enjoyed it! Thanks for the comment.

You're welcome! Thanks for the comment.

Thanks! I'm going a bit further being using the bank to charge my 24v battery bank via 24v AC charger. I want to see what the losses will be. I sure it will huge.

Looking forward to it..

You're very welcome. Thanks for the comment.

That is great! I'm glad there are other people that use these batteries to their greatest benefit. It takes a little more monitoring, but it's worth it. Thanks for the comment.

Thanks for this great experiment 👍 Stumbled on your channel. Great applications! Maybe you can answer my question because you’re know your battery stuff. I recently totally discharged my LIFEPO4 135 amps battery on a camping trip after 3 days of rain and virtually no sun . My 200watt solar blanket with mppt solar regulator. It couldn’t get the battery to “start up” even in full sunshine to accept the charge from the solar blanket. I used my victron 15amp blue smart charger using a small 100watt inverter connected to my car cigarette lighter and that worked. Could you explain why the solar blanket with appropriate controller could not?? Thanks 🙏🏻 so much Greetings from Oz!

​@Donpardo probably because you didn't have enough amps coming from the panel to activate the bms.

Completely agree, these people who tell us, you cannot use batteries in parallel or series, unless they are the same brand the same date the same time the same wattage, the same BMS are full of baloney, will Prouse and others have proven this wrong many times

I have continue to use 24 -100 amp hour batteries, Life PO4 in strings that equal 24 V system complete several different brands purchased at different times all equal individually and then in strings before parallel series, all work fine as long as they are wired correctly to a very large busbar positive and negative sides. No problems for several years. We have been sold bill of goods by the manufacturers.

Glad I can help. Thanks for the comment!

It will also last about 10 years! Thanks for the comment.

The thing I'm not sure of is if they will continue to do that the more I use the battery bank. Thanks for the comment!

Thanks for the great info!

@@OffGridBasement You are welcome ! Greetings from Greece. Keep up the nice videos !

Glad to help and thanks for the comment!

I believe you are correct. I just didn't want to stress the other BMS's by having them click off and on. Thanks for the comment.

Thanks for the info and the comment.

Good to hear. Equal cable is a best practice and how you wire up the bank can make a big difference in the total lifespan of all the batteries. Thanks for the comment.

Glad it was helpful! Thanks for the comment.

You're very welcome. Thanks again for the comment.

My take also. At least to the point that it's not written in stone, which is great for me as I have been buying mine one at a time as I couldn't afford them all at once. Started out with two Weize 12v 100ah LiFpo4, when I went to buy a third one they were all sold and gone, still, so I ended up getting a Power Queen of the same size and I'll probably do the same for my fourth which will complete my bank. So far the three of them seem to be playing well together and keeping a close state of charge. I take them off the panels and the load for an hour once a week to let them equalize just in case.

I like that I'm seeing I'm more free than previously thought as to battery size. I like to buy what's on sale.

I think for your system to be the "most efficient" it should have all the same battery brand and size. That way they all have the same BMS settings and internal resistance. In a pinch this will definitely work!

@Off Grid Basement i agree the same is best but it is a bit open ended. Im watching andy on offgrid garage stacking 2 wildly different battery sizes together and its working as well.

Yeah they might run out at extreme low voltage at different times but who goes that low in everyday use. Most try to stay above 20-30% SOC for battery longevity. No reason to not mix that I have experienced and seen. Exception would be extreme amp draw (say 50 amps for the entire life of the battery). That might cause an imbalance even with 2/0 wire between them.

You are very welcome! Thanks for the comment.

Thank you! 👍

Thanks for the comment! If I plan on using this type of battery setup for a while then I probably will end up using some of DC to DC converter. I'll be making a video soon about how much loss you get from going from DC to AC to DC...

Thanks for watching and thanks for the comment!

Thanks for the sub! You are correct. If you switched the fuse block with bus bars and larger wiring you could push the battery bank much harder. The thing you need to remember is your bank is only a powerful as the smallest battery. The 50Ah battery has a max discharge rate of 50amps. That being said I could probably push and pull 150 amps from this bank if I had proper bus bars and wiring. This fuse block has a max rating of 100 amps so I definitely don't want to try it!

@@OffGridBasement But, if the batteries compensate each other if they have 50 amps and 100, why not use 100ah at once? The 100ah will discharge 75 and the 50ah will charge 25ah, right?

Thank you and thanks for the comment!

Thank you for the great information! I appreciate your advice and comment.

If you run each battery through a fuse or breaker to a bus bar, using ample wire size, the internal resistance of the higher capacity battery will largely compensate for the difference in capacity. This is essentially what this video demonstrates and it is a known condition. The KEY is he's using the exact same chemistry, LiFePO4, and they started out with a basically identical voltage.

@@jasonbroom7147 I disagree with you a little. The twe lower capacity batteries clearly run out of juce before the bigger one. By changing the lengths of the cables and letting them have a little resistance (not too thick wire) they should keep on running to allmost the end all of them. If you take the initial 10.3A devided by 425Ah and multiply it with 50Ah you get 1.21A; with 100Ah you get 2.42Ah and 275Ah = 6.66A. It is clear that the smaller batteries are used harder than the big one to begin with as they where 50Ah = 1.55A; 100Ah = 3.33A and 275Ah = 5.55A. The 50Ah is 28% too high; the 100Ah is 20.6% too high and the 275Ah is 16.67% too low. In my oppinion it is best to use them all equally.

​@leonhardtkristensen4093 can help me please I have 280ah and 200ah battery how long should I have cable for each battery so they,are equally used please example. Thank you so much

@@897aa33 Firstly the two batteries are close in Ah value and there fore not that different. I believe you have two options about how to parallel connect them. You can connect them together with a big busbars or very thick and short cable. If you do this you must firs make sure that they have the same voltage before connecting to avoid a very high current flow (and getting a big spark). This will let the internal resistance in the batteries sort out the differences. This connection will also allow your inverter (or whatever you have connected) to draw a high current without a voltage drop in the cables. The second option puts in a fev safety points but may give a fev drawbacks as well. That is the longer cabeled option as used in this video. If you start by looking at the absolute highest current allowable to be drawn from the two batteries (take the smallest of the two) and use ohm's law you can find a resistance value for the cables that will prevent an over current between them. That will be 30v/current = resistance ( 30v is about the max allowable for two 12v batteries). You should then find the thickest cable you find reasonable , get the resistance value per meter (can be found online using Google searge). (roughly 1.8mOhm for a 10mm^2 wire 1m long.) (example 30V/100A = 300mOhm => appr. 300/1.8 = 167m cable) That is of cause impossible but if we only want to avoid a big spark when connecting and put the current up to 200A we could use 3v (it would be rare that a bigger difference excisted) it would be reduced to roughly 8.35meter. That is the total cable + and - . You would then devide the cable as follows (8.35m / 480) * 200 / 2 = 1.74m After that cut off 2 pieces of 1.74m and the rest 4.87m you would cut in half making 2 pieces of 2.345m You would use the longer cables to the smaller battery. You would then have a voltage drop of less than 1 volt at the common point drawing 200A from the 2 batteries parrallelled having over 2000watt usage. It is all a matter of choice. Not much in life is perfect. The main thing is that if you have a bit longer cable to the smaller battery then they will be better ballanced. Internal resistance in the batteries matter too of cause and that can be deducted from the individual cable lengths but the internal resistance will change with the amount of charge in the battery.

Yes. With this setup you wouldn't want to fully charge or discharge. I could get a lot of issues especially with full discharge. I try to keep the bank between 20% and 80%. Thanks for the comment.

Ahh so could I set my solar controller to 13.5v max charge and 12.5 max discharge to achieve this ?

I don't know if that would work. Good question though. Thanks for the comment.

You could connect them all directly. I did the fuse block so if one battery went nuts it would be cut off from the rest of the bank. You would also need much higher gauge wire if you connect them all together. The fuse block makes it so I can use much smaller gauge wire. I'm limited to 100 amps because of the block, but I don't have a problem with that. Thanks for the comment.

I’m thinking this is a much safer idea

You're welcome. Thanks for the comment.

Thank you for the info and the comment.

Very welcome! Thanks for the comment.

Glad it was helpful!

Those are all very valid concerns. This is really only a proof of concept video. If you're really going to do this you really need to know the specifics of each battery and work from there. I don't feel like it would damage the individual batteries more just because of the different amperages going to and from each battery. With this scenario you don't want to get below 5% SoC and you will probably never see 100% due to each battery having different BMS settings. Sorry I can't give more information.

You're welcome! Thanks for the comment.

If they are connected in parallel then you will have a very close idea of how the other battery is doing. If they are connected in series, then there will be more of a chance of not knowing exactly how the other battery is performing. Hope this helps!

I felt like it was easier to explain in this fashion. The voltage would've changed from the lack of draw. Thanks for the comment.

@@OffGridBasementI understood. And in the long term, how is it working now? I have a 150ah litokala which is actually 125 and I'm going to put together a pack of 280ah cells. I want to combine the two in parallel, would that be a good idea?

@@SSP-2027 It definitely won't hurt anything. Just watch your total capacity for a bit. I would plan on having a total of 400ah at the most.

First, excellent video- thank you! Individual battery voltage tests are not valid because all 3 batteries are connected together which is the opposite of "individual". You are only measuring the voltage drop of the connecting wires because all positives are connected together. You are basically checking the voltage of each end of the same wire. If you disconnected the batteries when the current dropped to zero, you would have measured zero volts at those batteries because the BMS disconnected the cells from the terminal. But your measurements remained constant (the voltage of the other 2 batteries). Thanks again for a great, informative video!

Go for it. I believe it will work just fine. Thanks for the comment.

You would just fine wiring them in parallel as long as they are both 12v batteries. Thanks for the comment!

Everything about that would work fine. Make sure to have a fuse between the battery bank and inverter. Thanks for the comment.

Yes it will. Make sure the batteries are the same chemistry. Thanks for the comment.

Self leveling is from all batteries being connected in parallel. The larger the capacity, the lower the resistance, so it accepts more current. I hope that helps!

Thanks for the info and the comment.

Yes. I don't want to discharge this bank all the way. It can start to act erratic. Thanks for the comment.

Yes. A 12v to 12v charger would be the way to go. I'm going in that direction after finding out what the losses are with DC to AC back to DC.

@@OffGridBasement great….you have to do a video. right :)?

The wires never got hot when I charged the whole bank with 30 amps. I'm sure if I got it to charge a single battery @ 30amps the wiring would get pretty warm.

@@OffGridBasement I’ve been warned from Will Prowse to never mix batteries, because you need to keep all your charge controller settings the same, which wouldn’t happen with different manufactures! But I realize you’re only using them to extend your system.

@@simon359 since these are all Lifepo4 batteries you should be able to use the same settings for the entire pack. Definitely don't mix SLA and Lifepo4 batteries! Will is definitely the authority!

@@OffGridBasement Sorry, but if you use the same charge control settings for three different size batteries, you will destroy the batteries! From my understanding, they all have to be able to use the same dialed in settings, there can’t be multiple settings on a charge controller!

@@simon359 I'll have to give it a try. That is what this channel is all about! Thanks for the info!

Some things that are easy to understand for some don't come so easily to others. Thanks for the comment.

My 24v system is the best and I totally agree. 12v is the hardest and most expensive way. Thanks for the comment!

You're correct. I figured the voltage testing was really going to show much individually, but I wanted to show it anyway. It's really the current draw from each battery is the main point of the video. Thanks for the comment.