Bafang error 42: Battery total voltage too low
Bafang CAN systems (M400/M500/M600/M620, DP C18 CAN, 850C/860C CAN)WarningRide with caution
The BMS reports the pack voltage is below its minimum. The battery is either empty, deeply discharged after storage, or sagging under load. Assist is cut to protect the cells.
Likely causes
- Battery empty
- Pack stored empty for months and self-discharged below the cut-off
- Aged cells sagging under load
- Cold weather reducing available voltage
How to fix Bafang error 42
- Charge the battery fully; if the charger does not start, let it sit connected 30 minutes (BMS may need to wake)
- Reduce assist level and see if the code stops
- Store the battery at 40-70% charge in future
- Have the pack tested if a full charge still trips the code under load
Go to a dealer if: Go to a shop when a fully charged pack still shows 42 under load, or when the charger refuses to charge it.
Warranty: Battery warranty covers premature capacity loss; deep discharge from storage neglect usually does not.
Typical cost: Free if charging fixes it; battery replacement EUR/USD 300-700.
Warranty: Battery warranty covers premature capacity loss; deep discharge from storage neglect usually does not.
Typical cost: Free if charging fixes it; battery replacement EUR/USD 300-700.
Still stuck? Take a photo of the display and show it to a local e-bike workshop. Bring the bike's system name (e.g. Bosch Performance Line CX) and the exact code; that saves diagnostic time and money.
Frequently asked
Can I reset error 42?
Charge the battery; the code clears when voltage is back in range.
Can I keep riding?
Only very gently; repeated deep sags damage the pack.
Warranty?
Yes if the pack is within warranty and was not deep-discharged by neglect.
Related Bafang codes
Not an official Bafang document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.