About this replacement
AL-KO 38.4LI / DC-3630LI Series — 36V Li-ion Replacement Battery (91132807)
This is a 36V 5000mAh (180Wh) Li-ion replacement battery for AL-KO cordless lawn mowers. It fits the 38.4LI, DC-3630LI, Comfort 38.4 Li, and over 80 additional AL-KO models that share the same 36V platform and battery bay. OEM part numbers covered include 91132807, 113124, 113126, 113280, B150, and B200.
- 36V platform compatibility: These AL-KO models share a common 36V nominal rail, identical battery bay dimensions, and the same BMS communication handshake. Swapping across any model in this family works without modification because the connector pinout and charge acceptance protocol are identical across the range.
- Bench tested on actual hardware: We ran this pack through full charge-discharge cycles on a 38.4LI deck, monitoring BMS cutoff thresholds under simulated blade-motor inrush loads. The BMS held stable under repeated start events and did not trip at rated current draw on a clean, dry-grass load.
- Cold-weather start tip: Before the first mow of the season, bring the battery indoors overnight if temperatures are below 10°C. Cold Li-ion cells carry higher internal resistance, and the blade motor's inrush current spike can trip the BMS on a pack that hasn't warmed up. Ten minutes at room temperature is enough to lower resistance back to normal operating range.
BMS cutoff under thick or wet grass — what's actually happening
When the blade hits dense or wet grass, the motor draws a surge of current well above its steady-state load. If that spike exceeds the BMS overcurrent threshold — typically triggered within milliseconds — the pack cuts power to protect the cells. This is not a fault in the battery; it is the BMS doing its job. The fix is to slow your forward pace so the blade isn't taking on too much material at once, which keeps current draw below the trip point. On heavily overgrown lawns, mow in two passes rather than one to keep motor load in the safe range.
Charger showing a fault light after the mower sat in storage all winter
Li-ion packs left in a garage over winter can self-discharge below the charger's acceptance voltage threshold — often around 2.5V per cell. When voltage drops that low, the charger sees the pack as defective and refuses to start a charge cycle. Some AL-KO chargers will recover a low pack if you hold the charge button for 10–15 seconds to force a trickle-charge initiation; check your charger model for this function. If the charger accepts the pack after that, allow a full charge cycle before use. If the charger still rejects the pack, measure total pack voltage — a reading below 25V across the terminals indicates cells have dropped too far to recover safely.