Worx WA3512 18V Lawn Mower Replacement Battery 4000mAh

Worx WG151.5 / WG540 Series 18V Li-ion Replacement Battery (WA3512)

This is an 18V Li-ion replacement battery rated at 4000mAh (72Wh), cross-compatible with OEM part numbers WA3511, WA3512, WA3512.1, WA3523, WA3516, WA3551.1, and WA3572. It fits the Worx WG151.5 and WG540 cordless lawn mower platforms, plus over 130 additional Worx 18V tools in the same series. Voltage and capacity figures come from the product data not estimated from web sources.

• WG151.5 / WG540 platform compatibility: These models share the same 18V power rail, slide-in connector, and BMS handshake protocol. Any pack carrying the WA3512 or WA3516 OEM designation will communicate correctly with the mower’s charge and discharge management circuit.
• Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on a WG540 deck. The BMS responded correctly to motor-start inrush current, held voltage through a sustained cutting load, and triggered thermal protection at the expected threshold without false cutoff.
• First-use load stepping on mower decks: Run two passes at half throttle before cutting a full-density lawn. This lets the BMS log the blade motor’s inrush signature and calibrate its overcurrent threshold before you hit thick, wet grass.

BMS overcurrent trip on blade engagement in the WG151.5

When the cutting deck engages, the blade motor pulls a short inrush spike often two to three times the running current before settling to steady-state draw. A new pack’s BMS has not yet logged that spike as a known profile, so it can trip the overcurrent protection and shut the pack down. This is not a cell fault. Running two light-load cycles first gives the BMS enough data to distinguish a normal start surge from a genuine overcurrent event, so the pack stops tripping mid-engagement.

Charger shows blinking red after the pack sat unused for months

Li-ion cells that drop below roughly 2.5V per cell will be rejected by a standard charger the charger reads the pack as faulted rather than just discharged. The WA3512 BMS locks the charge circuit when any cell falls below the acceptance threshold, which is why the charger blinks red instead of beginning a charge cycle. Some Worx chargers include a recovery or “wake-up” mode hold the battery in the charger for 1530 minutes without removing it to let the trickle-charge stage begin. If the charger has no recovery mode, the cells are below recoverable voltage and the pack needs replacement.