New lifepo4 diy build... Parallel packs slightly different charge/discharge rates

[ericfx1984]

So I recently built the batteries that you can see in my signature.. they run the same bms's and have all the exact same connections and same wire lengths etc

However consistently one of them seems to charge/discharge about two and a half percent slower

For instance last night I had a full charge before the sun went down.. by this morning the app showed that battery one was at about 180 amp hours while battery too was at about 186 amp hours

Now both of these batteries were tested individually and they both tested well above the 230 amp hour mark.. but I was never able to fully discharge them due to my test rig not really being able to handle the low voltage high amperage... No big deal as they definitely both had more than full rated capacity

So is this something that is a problem with the app itself? Or are they just slightly out of whack as far as actual capacity and therefore state of charge goes?

I'm not too worried about it since I never get anywhere near full discharge I think I've seen as low as 65% since installing them

But it brings up the question is there something that will just get worse over time and should be looked at or is this okay not a big deal? Or should I consider doing something to balance the two packs out amongst each other?

 

[time2roll]

This is normal. Never going to be perfectly exact due to a multitude of very small differences. There should be no significant impact on the full capacity.

 

[ericfx1984]

This is normal. Never going to be perfectly exact due to a multitude of very small differences. There should be no significant impact on the full capacity.

I kind of figured.. I think really the only thing that I could see happening is if I did do a full drawdown which I don't anticipate doing but if I did one battery would shut off when it hit the low voltage disconnect and then the other one would shut off probably minutes later as the remaining load was transferred to it

 

[time2roll]

I kind of figured.. I think really the only thing that I could see happening is if I did do a full drawdown which I don't anticipate doing but if I did one battery would shut off when it hit the low voltage disconnect and then the other one would shut off probably minutes later as the remaining load was transferred to it

Yes especially as the pack voltage gets into the sub 12.5 zone any accumulated voltage spread should come back together and balance capacity and both would shut down very close to each other.

 

[Denis]

So I recently built the batteries that you can see in my signature.. they run the same bms's and have all the exact same connections and same wire lengths etc

However consistently one of them seems to charge/discharge about two and a half percent slower

For instance last night I had a full charge before the sun went down.. by this morning the app showed that battery one was at about 180 amp hours while battery too was at about 186 amp hours

Now both of these batteries were tested individually and they both tested well above the 230 amp hour mark.. but I was never able to fully discharge them due to my test rig not really being able to handle the low voltage high amperage... No big deal as they definitely both had more than full rated capacity

So is this something that is a problem with the app itself? Or are they just slightly out of whack as far as actual capacity and therefore state of charge goes?

I'm not too worried about it since I never get anywhere near full discharge I think I've seen as low as 65% since installing them

But it brings up the question is there something that will just get worse over time and should be looked at or is this okay not a big deal? Or should I consider doing something to balance the two packs out amongst each othe

edit: Deleted,