Flyer C10 E-Bike Replacement Battery 25.2V 18Ah Li-ion

Flyer C10 / C11 / C12 HS Series — 25.2V Li-ion Replacement Battery

This is a 25.2V, 18000mAh (453.6Wh) lithium-ion battery for the Flyer C10, C10 HS, C11 HS, C12 HS, and over 37 additional Flyer e-bike models. It replaces the original pack when cells have degraded and the bike can no longer complete a full ride without cutting power. Voltage and capacity match the factory specification for these frames.

• C10 / C11 / C12 HS platform fit: These models share the same 25.2V battery rail, frame dock, and BMS handshake protocol. A single pack covers the full range because the motor controller accepts the same charge profile and connector across all three lines.
• Bench tested on actual hardware: We cycled this pack through motor-assist load profiles, including sustained hill-climb draw. The BMS held cutoff thresholds correctly and recovered cleanly after simulated low-cell-voltage events.
• First charge after winter storage: If the bike has sat through a cold season, charge the pack at a low rate before the first ride. Cold Li-ion cells have elevated internal resistance — fast charging below 10°C causes lithium plating on the anode that permanently cuts cycle life.

Motor cutting out mid-hill on a new battery

A sustained climb pulls more current than flat riding. If cell groups inside the pack are even slightly unbalanced, the BMS reads a voltage drop on the weakest group and trips the output to protect those cells. This looks like a sudden power cut rather than a gradual fade. On a new pack, this can also occur if the battery shipped partially discharged — run a full charge cycle first and the BMS will balance the groups before the next ride.

Charger LED stays green instantly and pack shows no charge

A charger that flashes green immediately after connection is not completing a charge — it is rejecting the pack. This happens when cell voltage has dropped below the charger's acceptance threshold, usually after extended storage. Connect the charger and leave it for 30 minutes without interrupting the connection. Most Flyer chargers will begin a recovery charge once the BMS detects enough input voltage to re-initialise, typically above 20V at the pack terminals.