Switched ADC BMS

[johu]

Pretty cool idea. Since balancing only makes sense when there is no current flow there is also no risk of missing an over voltage event.

[johu]

Now after running 6 modules in my ESS for some weeks with old, high R_int LFP batteries there are some observations:

- it is dead stable, even over multiple power cycles and even with some 2.1 modules in there
- SoC calculation is all over the place. Sometimes it estimates when there's still current flowing
- SoH calculation is completely off
- Charge curve parameters need to be tuned carefully to avoid oscillation. Will attach my configuration later
- It would be good to have hysteresis. So when ucellmax is reached it should output 0 charge setpoint until ucellmax-threshold is reached
- internal resistance estimation could come in useful