About this replacement
Kobalt Cordless Push Lawn Mower — 40V Li-ion Replacement Battery
This 40V 4.0Ah lithium-ion pack replaces the KB2540C-06 and related batteries used in Kobalt's 16-inch, 19-inch, and 20-inch cordless push mowers. At 160Wh, it matches the original capacity these mowers pull against during full cutting sessions. The 40V Max platform means this same pack moves between compatible Kobalt tools without an adapter.
- Cross-model compatibility (16", 19", 20" mowers): These mowers share the same 40V Max battery rail, connector pinout, and BMS handshake — one replacement covers all three platforms.
- Bench tested on actual hardware: We ran full charge/discharge cycles across the compatible mower platform — the BMS held voltage stable under motor load and triggered the low-voltage cutoff cleanly without false shutdowns.
- First charge on a new Li-ion mower battery: Run a full charge before the first cut, then let the pack discharge fully on the mower before charging again — this helps the BMS calibrate its state-of-charge readings from the start.
Why mower batteries drain faster than other 40V tools
Lawn mowers draw current in sharp bursts — especially through thick or wet grass. These spikes pull harder on individual cells than sustained loads from drills or trimmers. The BMS in this pack is rated to handle those peaks without throttling output mid-cut. Keeping blades sharp reduces motor load, which directly reduces draw on the battery per pass.
Mower stops mid-cut but the battery shows charge remaining
This usually points to a voltage sag under load — the pack's resting voltage reads fine, but cell voltage drops below the BMS cutoff threshold the moment the motor spikes current demand. It happens most often in aging packs with degraded cells. A replacement pack with fresh cells restores the headroom the BMS needs to stay above that cutoff during heavy pulls through dense grass.