Page 6 of 6

Re: BMS Details

Posted: Thu Jan 04, 2018 5:23 pm
by miscrms
Sorry to dredge up this old thread, but there's a lot of great info here. The schematics as drawn sort of make it look like the monitor for every set of 8 cells is independent, but I'm gathering that this is not really true. From studying the board photos, L50 for example on the far left input of IC32 is really the first of the 4 input inductors on IC31 not a fifth inductor on IC32. So each IC is chained together down the whole line in the same manner that IC33 and IC32 are until you get to the mid point split.

I'm looking at using my 48 Leaf modules in an 8s6p configuration and just want to see if I've got my options straight if I wanted to try and use the stock BMS.

From easiest to hardest:

1. Bypass one section: Use 4 ICs / 17 taps and bypass the rest of the ICs. Each tap will be connected to 6 batteries in parallel, so balancing will be 1/6 as effective as stock.

2. Bypass two sections: Use 4 ICs / 17 taps from each 1/2 of the board, 8 ICs / 34 taps total, bypass the rest of the ICs. Battery would be split into two 8s3p sub packs wired in parallel, each tap will be connected to 3 batteries in parallel so balancing would be 1/3 as effective as stock.

3. Major modification: Use all ICs / taps. Board would have to be modified to cut the connection between the high/low taps after each 4th IC to avoid blowing the trace and/or damaging ICs. Would need to add the missing sense point and filter inductor at the top of each set of 4 ICs. May also be an issue with the comm line between the same 2 chips, i.e. the output of the top chip on one string to the input of the bottom chip on the next string. Might need a level shift? Battery would be divided into six 8s strings in parallel, with each tap connected only to 1 battery so balancing would be as effective as stock.

Thanks for any input,
Rob