Brake chopper

A circuit that bleeds off excess energy from regenerative braking into a resistor (which converts it to heat). Without it, braking on a full battery while going downhill can push voltage above the BMS limit - triggering an overvoltage cutoff.

Why it matters

Start a ride at the top of a hill with 100% battery. Brake going down. The regen charges a battery that’s already full. Voltage spikes. Without a brake chopper, the BMS may cut power to protect cells. With one, the excess energy gets dumped as heat instead.

Which wheels have it

Very few consumer EUCs include brake choppers. It’s more common in industrial motor controllers. Some community members have discussed DIY solutions.

555 take

If you regularly start rides at full battery on hills, this is worth understanding even if your wheel doesn’t have one. The fix: don’t start downhill rides at 100%. Charge to 90% or ride flat first to use some capacity. For rider-level practice, the regenerative braking deep dive is the useful next read.