Andrewol wrote:Is it necessary to discharge overcharged cells during balancing?
No, there are several other methodologies, but this one "bleeding" aka passive or resistive, is implemented on 99.99% of the BMSs and balancing chargers.
> Perhaps better to share the current with undercharged ones via parallel connection.
aka "capacitive", "charge shuttling" and "active charge-transfer balancing"
good in theory, but hard (perhaps expensive?) to implement well in practice
The "non-protective BMS" dedicated balancing gadgets often go this way.
Actual net energy saved is minimal, perhaps relevant in an off-grid solar-only setup
The third type is "shunt based" apparently Zephyer BMS implements that well.