Seems great being able to double or quadruple battery packs by charging to 4.0 or 4.1V per cell group,
but it seems almost all the normal (<$30) BMS'es out there don't balance unless going all the way to 4.2V -- and perhaps the bulk charging is not perfectly precise, and then a specific group is never even seeing the 4.2V level to trigger the BMS'es balance function.
It seems that having a configurable balance point (either a hard switch/jumper) would solve this -- otherwise, you'll unlikely be working the pack correctly and then stressing some cells more than others.
Ideally, you'd want the BMS to see the "bulk charge rate", divide this by the series count, and say : each cell group stops at this voltage, and properly starts saturation once getting to this, throwing the rest of the energy away or to the other cell groups. Balancing down via resistance seems stupid.
I see the bluetooth BMS that some have linked to ~$40-50 on AliExpress with a configurable balance point. Not all that fanciness needed for a normal battery though.
Thoughts?
but it seems almost all the normal (<$30) BMS'es out there don't balance unless going all the way to 4.2V -- and perhaps the bulk charging is not perfectly precise, and then a specific group is never even seeing the 4.2V level to trigger the BMS'es balance function.
It seems that having a configurable balance point (either a hard switch/jumper) would solve this -- otherwise, you'll unlikely be working the pack correctly and then stressing some cells more than others.
Ideally, you'd want the BMS to see the "bulk charge rate", divide this by the series count, and say : each cell group stops at this voltage, and properly starts saturation once getting to this, throwing the rest of the energy away or to the other cell groups. Balancing down via resistance seems stupid.
I see the bluetooth BMS that some have linked to ~$40-50 on AliExpress with a configurable balance point. Not all that fanciness needed for a normal battery though.
Thoughts?