About this replacement
Husqvarna Automower G1 — 12V Ni-MH Replacement Battery (535 0636-01)
This is a 12V, 4000mAh Ni-MH replacement battery for the Husqvarna Automower G1 robotic lawn mower. It fits models from 1998 through to later G1 variants and replaces OEM part numbers 535 0636-01 and 535 0962-01. Capacity is 48Wh — same as the original pack.
- Automower G1 series compatibility: The G1 platform across 1998, 1999, and 2000 production years uses the same 12V battery bay, connector, and BMS handshake. All G1 variants draw the same voltage rail to power the drive motors and blade deck, so one battery covers the full G1 range.
- Bench tested on actual hardware: We ran the pack through the Automower G1 charge cycle and confirmed the BMS accepted the cells without fault codes. Load testing across drive and blade motor draw showed voltage held stable under normal mowing conditions.
- Seasonal storage tip: Ni-MH cells self-discharge faster than Li-ion — at roughly 1–2% per day at room temperature. If the mower sits unused for more than six weeks, run a partial charge cycle before returning it to the dock to prevent the cells dropping into a recovery-charge state.
Charger showing fault light after the mower sat in the garage all winter
Ni-MH packs left uncharged through winter will self-discharge to a point below the charger's acceptance threshold. The Automower dock interprets this as a fault and refuses to begin the main charge cycle. Most docks have a trickle or recovery mode — leave the mower seated in the dock for 30–60 minutes without disturbing it. Once cell voltage climbs above approximately 10V, the dock should switch to its normal charge cycle automatically.
Mower cuts out mid-row then restarts on its own
This is thermal protection firing, not a battery fault. When the blade motor hits dense or wet grass, inrush current spikes and the BMS trips the pack to protect the cells. The mower pauses, the BMS resets, and the unit resumes. Let the mower cool for five minutes before sending it back out. If the cut-outs become frequent, check for grass buildup under the deck restricting blade rotation — that sustained drag is what keeps pushing current above the BMS threshold.