Using Packs of Different Amp hour ratings.

[BiGH]

Hey Endless-spheroids,
Just wondering if it is possible to keep packs of different amp hours of capacity connected (and reilable) in either series or parallel. I currently have 2x 36v 12ah packs. I've got another pack on order.

I was thikning about this - what would happen if my other pack was a 20ah pack?

Could i wire the two 12ah packs in SERIES for 72v, and have the 20ah wired in series for 72v - then parallel both off the controller?

would this mean that if the BMS tripped on one it would see the full pack voltage of the other? (ie fried components?)

The reason i'm thinknig of doing this is so that i can reduce the discharge rate of the pack.

It would be easier to run two sets of packs of the same amphourage, however if one tripped before the other i'd be worreid.

ie should it be 2s2p or 2p2s? and mismatched?

 

[BiGH]

nothing..? looks like i'm going to have to wait for the canadians, americans and English to WAKE UP!!! hehehe.


reading on the yesa site, it states that the packs shouldnt be paralleled, as all of the strain will be put on one side of the series when the pack is cutoff.

but to me, if the maximums the pack can take individually is more than enough then it shouldn't be a problem!

 

[vanilla ice]

Looks good to me!

Heres xy's 22a unmatched setup, 10+12=22. So you should get 32a total out of yours! For ease of comparison ignore the 8v series bat..

 

[BiGH]

its more the BMS i'm worried about - if one side of the pack cuts out, then this would mean that the + and - would be 72v still from the other pack. wouldn't this then mean the bms is seeing 72v? frying the fets?

 

[fechter]

I think it will work fine like drawn. If one BMS trips, only half the pack voltage will be across it (unless the BMS on the other side also trips).

I might recommend adding a wire across the between pack connections just to help keep the packs balanced and the BMS happy.