Re: Extra Battery, How to Integrate with 24kWh Traction Battery?
Posted: Tue May 22, 2018 10:48 pm
I take it your modules (VW ones I think you mentioned?) are all from a single vehicle then, and thus well matched to each other? The individual cells within each 8s module are well matched to each other, but my concern is the total 12s(8s) pack, where each group of 8 cells might be a different capacity than another.mux wrote:That is not a normal mismatch, that sounds like heavily used modules. Typically, at beginning of life cell mismatch in a pack is at most a couple tenths of a percent.
If cells were 3% apart like yours, you'd need balancing current in the order of ~0.3% of the charge current in normal use (that seems to be the rule of thumb BMS engineers have decided on, it seems to work for car and bike batteries). The Leaf has a BMS that can only do something like 15mA per cell, i.e. on the old 58Ah cells that's just 0.025% of nominal capacity.