FYI, a word of caution following an unfortunate experience... If you leave the original Chevy volt BMB on the 5kWh block from a Chevy volt pack, and disconnect the bus bar links that connect the 2kWhr modules and the 1kWhr module together to become a 5kWhr assembly. It will discharge the bottom three cells in one of the 2kWhr modules. I just learned this the hard way... On two packs at the same time...
I haven't studied the root cause in detail and don't plan to but it appears to be due to the fact that the 5kWhr BMB splits cell sensing across 4x isolated ASICS that handle sensing for the 3x modules within the 5kWhr assembly. So by electrically isolating those smaller modules I also would have split the connections to at least one of those ASICS. I expect that as a result of doing this the cell balancing circuitry latched on or something else within the BMB started operating with vastly increased current draw.
This only seems to be a problem for 3 of the connected cells, but i didn't catch this until those three cells were all discharged below 3V, one of them just shy of 2V. :-(
I haven't studied the root cause in detail and don't plan to but it appears to be due to the fact that the 5kWhr BMB splits cell sensing across 4x isolated ASICS that handle sensing for the 3x modules within the 5kWhr assembly. So by electrically isolating those smaller modules I also would have split the connections to at least one of those ASICS. I expect that as a result of doing this the cell balancing circuitry latched on or something else within the BMB started operating with vastly increased current draw.
This only seems to be a problem for 3 of the connected cells, but i didn't catch this until those three cells were all discharged below 3V, one of them just shy of 2V. :-(