AFTER regular charging (to 100%) and the charger’s LED is green, the charger will continue delivering a minimal current, so the BMS (Battery Management System) can do its job.
The BMS will balance out the amount of Volts in every cell as well as possible, so they all carry the same/similar amount of power. This is a slow process, So it’s advised to leave it hooked up to the charger for a additional 4~8 hours. This is not needed at every recharging session, but it’s depends on your use: daily commuter or weekend fun driver? On average it’s recommended to balance once every 5~8 recharges.
In the attached image you see:
Left: unbalanced: visually its even clear it is not optimal use of the capacity of every cell.
Middle: passive balancing: (slowly fill all cells simultaneous the same and when one reaches its maximum stop charging all).
Right: active balancing: fills each cell to its max, compares them, then tries to empty the highest a bit and use that energy to top up the lowest a bit. It’s trying to optimally use the already-present energy in your battery-pack.
There is more going on in the background, but this is generally how battery balancing works.
So by showing your 🔋a bit of ❤ and keeping it balanced, it will reward you in return with a longer lifetime.
Short version:
Leave your charger connected for 4~8 hours AFTER indication full (eg. a green light) once every 5 to 8 charge cycles. It will prolong your battery lifetime – the most expensive & precious part of your eBike.