Also called: BMS, battery protection
What it does
It stops the battery charging too far, draining too low, getting too hot or giving too much current, and balances the cells. When it acts, the battery can switch itself off suddenly.
Signs of a problem
- Bike shuts off suddenly, often on a hill or at low charge
- Battery shows full on the charger but the bike reads empty
- Battery won't charge after sitting empty a long time
Safe things to check
- Charge it fully with its own charger.
- Let a very hot or cold battery reach room temperature before charging.
Looking after it
- Don't leave a battery fully empty for long; that's when protection can lock it out.
- Never bypass or open a BMS; it's what keeps the pack from overheating.