Bring lithium-ion batteries from cordless mowers, trimmers, and blowers indoors for winter, store them at roughly 40 to 60 percent charge in a dry spot between about 40 and 80 degrees, and never charge a battery that is below freezing. Check each pack for swelling or cracks before storage, and follow your tool maker's manual where it gives different numbers.
Why winter storage matters
Lithium-ion packs age fastest when they sit fully charged, fully empty, hot, or very cold. A battery left on a cold garage shelf for four months at full charge can lose noticeable capacity by spring. A pack left completely drained can drop below a safe voltage and refuse to charge. Storing at partial charge in moderate temperatures slows both problems.
| Storage condition | Effect |
|---|---|
| Indoors, 40 to 60 percent charge, cool and dry | Best long-term health |
| Full charge in a hot shed | Faster capacity loss |
| Fully drained for months | Risk of deep discharge; charger may reject it |
| Unheated garage below freezing | Usually survivable in storage, but never charge cold |
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Lithium-ion packs store a lot of energy, and damaged or abused batteries can overheat and catch fire.
- Inspect before storing. Retire any pack that is swollen, cracked, leaking, very hot after light use, or was dropped hard. Do not charge it. Take it to a battery recycling drop-off or household hazardous waste site; never put it in household trash or curbside recycling.
- Never charge below freezing. Charging a cold lithium-ion cell can cause internal damage. Let a cold pack warm to room temperature for a few hours first.
- Do not leave packs charging unattended for long periods, and charge on a hard, non-flammable surface away from curtains, paper, and fuel cans.
- Keep terminals covered and away from loose metal like keys, nails, and screws that could short them.
- Store away from exits and fuel. Keep packs off the floor, away from gasoline, propane, and oily rags, and not under the stairs or beside the only door out.
- Add a heat alarm in garages and workshops. Smoke alarms false-alarm from dust and exhaust there; heat alarms are made for those spaces.
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A simple end-of-season routine
- Run or charge each pack to about half. Many chargers show bars; two of four bars is close enough.
- Clean the tool and battery contacts with a dry cloth. Brush grass and dust out of vents.
- Store packs indoors in a closet, basement, or utility room, ideally in a fire-resistant bag or on wall mounts that cover the terminals.
- Store tools separately in the garage or shed. See our guide to wall-mounted garden tool organizers.
- Check charge every two to three months and top up to about half if it has dropped.
- Before spring use, let packs reach room temperature, then charge fully.
Getting more seasons from each pack
Batteries are the most expensive part of most cordless systems, so a little care helps. Avoid running packs completely flat during the season, let a hot battery cool before charging it, and keep packs out of direct sun in a hot truck bed or on a dark patio. If you own several tools on one platform, rotate packs so each gets used rather than one wearing out while others sit.
Snow tools are different
Cordless snow blowers and shovels run in winter, so their packs go out in the cold. Keep spares indoors, take them out only when needed, and bring them back in to warm before charging. Our guide to snow blower prep before the first snow covers gas and battery models.
Gas tools
Gas mowers and trimmers need fuel stabilizer or an empty tank, fresh oil, and a sharpened blade. See how to winterize a lawn mower.
Bottom line
Inspect, charge to about half, and store lithium-ion packs indoors between about 40 and 80 degrees, covered and away from metal and fuel, and never charge a frozen pack. Your batteries will hold more runtime in spring and the garage stays safer. For blade care before storage, read cleaning and sharpening garden tools before winter.
Related reading
- Cordless string trimmers for lawn edges
- Cordless hedge trimmers for fall shrub shaping
- Leaf blowers for fall yard cleanup
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