Symptoms
- Mower used to run a full lawn on one charge, now doesn't
- Battery drains faster in hot or cold weather
- Runtime has gradually decreased over a season or more
- Battery indicator drops quickly even at moderate use
Likely causes
- CommonNormal battery capacity agingLithium batteries lose some capacity every charge cycle, more noticeably after 2–4 years of regular use.
- CommonMowing thicker or taller grassHeavier cutting load draws more current and shortens runtime per charge.
- PossibleExtreme temperaturesVery hot or cold weather reduces lithium battery efficiency temporarily.
- PossibleBattery not charged to full capacityAn incomplete charge cycle or worn charger can leave the battery short of full.
What to do
- Confirm the battery is charging to 100 percent by watching the charger's indicator light fully complete before removing it.
- Raise the cutting height slightly if mowing thick or tall grass to reduce load on the battery.
- Avoid mowing in extreme heat or cold when possible, since battery efficiency drops in both conditions.
- Check the battery contacts for cleanliness on both the pack and mower.
- Track runtime over a few mows to see if the decline is gradual (normal aging) or sudden (possible fault).
- Consider battery replacement if it's several years old and runtime has dropped significantly and consistently.
Tools and parts
Replacement battery packSearch: “cordless lawn mower replacement battery”
When to call a pro
If runtime drops suddenly rather than gradually, a dealer can test whether the battery or the mower's motor draw is at fault.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.