How to Store Cordless Garden Tool Batteries Over Winter

For winter, remove the battery from the tool, check it is undamaged, and store it indoors in a dry place away from direct sun, heat and freezing temperatures. Keep the charger separate. The one point where makers disagree is charge level: STIHL says to store at 40 to 60 percent, DEWALT says to charge fully before storing for more than six months, and Battery University recommends about 40 percent for long-term storage. Because the advice differs, the manual for your brand settles it. The rest of this guide covers the routine and the gear that helps.

What the Sources Agree On

Across STIHL, DEWALT and Battery University, the same basics appear.

• Take the pack off the tool. STIHL says to remove the battery from a cordless tool before storage, and DEWALT says to disconnect the battery from the tool before extended storage.
• Keep it dry and cool. DEWALT says a cool, dry location, away from liquids, oils and extreme temperatures. STIHL says dry, out of direct sunlight, and in a closed box or a dry basement, garage or insulated shed. It does not recommend outdoor storage.
• Avoid heat. Battery University says heat causes the most permanent loss of capacity and shows that a pack kept warm for a year loses more than one kept cool.
• Do not store a damaged pack. DEWALT says not to use a battery with visible damage or cracks, and not to attempt repair. It should go to a service center.
• Do not let it freeze. Battery University advises avoiding freezing for any battery type.

Where Makers Differ: Charge Level

These can look contradictory, but they reflect different packs, different battery management systems and different storage periods. Do not average them. Look up your tool's manual or the maker's support page, and follow that for your brand. If you cannot find an answer for your brand, ask the maker rather than guessing.

A Winter Storage Routine

1. Finish the season. Run the pack through its last use in the fall, then take it off the tool.
2. Inspect it. Look for cracks, swelling, leaks or damaged terminals. Do not store or charge a pack that looks damaged. Contact the maker's service center.
3. Clean it. STIHL suggests wiping dirt from the pack with a damp cloth. Make sure it is dry before storing.
4. Set the charge level per your manual. Use your maker's guidance. If the pack has charge-level lights, STIHL's 40 to 60 percent corresponds to two lit LEDs on its packs; other brands use different indicators.
5. Warm cold packs before charging. STIHL notes that its batteries only charge above 5 degrees C (41 degrees F). A pack that has been in a freezing garage should come to room temperature before it goes on a charger.
6. Store in a case or on a rack indoors. A dry basement, closet or insulated space is better than an unheated outbuilding. Keep it out of reach of children.
7. Store the charger separately. STIHL says to store chargers apart from batteries. Unplug it.
8. Set a reminder. Check the pack through winter according to your manual's advice on frequency.

Temperature Limits to Know

STIHL gives a battery storage range of -10 to 50 degrees C (14 to 122 degrees F), and a range of 5 to 40 degrees C (41 to 104 degrees F) for chargers. It also says outdoor storage is not recommended. Battery University gives about 15 degrees C (59 degrees F) as the recommended storage temperature for most batteries, with a wider extreme allowable range. Those figures are STIHL's and Battery University's own, so check your maker's limits. The practical takeaway: a cool, dry room indoors is better than a garage that swings from hot to freezing, and a hot attic or a parked car is worse still.

What to Avoid

• Heat. Battery University reports that a lithium-ion pack stored at 40 percent charge kept about 96 percent of its capacity after a year at 25 degrees C, against about 85 percent at 40 degrees C. Those are its figures for a general lithium-ion cell, not your tool's pack, but the direction is clear: warm storage costs capacity.
• Weeks on the charger. Battery University says sitting at full charge, including while plugged in, shortens life.
• Running a pack flat and leaving it. STIHL says storing at a very low charge is also harmful.
• A cold garage shelf. Both STIHL and Battery University warn against outdoor or freezing storage.

Gear That Makes Storage Easier

You do not need special equipment, but a few things reduce mistakes:

• A hard plastic case or bin. It keeps the terminals covered and the packs together. Use one that suits your pack's size, and avoid loose metal objects in the same bin.
• A wall rack. Some racks are designed for a particular brand's packs. Check the listing for which packs fit, because racks for one platform often do not fit another. Our battery platform guide explains why the brand matters.
• A label and marker. Mark the date of the last charge so you know what has been checked.
• A shelf off the floor. Keeps packs away from damp concrete and spills.

Do not buy used packs to save money. Their history is unknown, and damage is not always visible. Chargers and cases are different, and secondhand cases are fine if they are clean and intact.

Which Tools Are Affected

Everything with a removable pack follows the same logic: trimmers, blowers, hedge trimmers, saws and cordless mowers. If you are deciding between a corded and a battery tool, our corded vs battery tools comparison explains how that choice affects storage. Tools with built-in batteries are different. For its integrated-battery tools, STIHL says to switch the tool off, pull out the activation key and store it separately, and keep the tool dry and out of the cold. Check your manual for yours. For examples of cordless tools that use removable packs, see our cordless string trimmer and battery hedge trimmer guides. If you are buying a new platform this winter, our Black Friday and Cyber Monday plan covers what to compare before ordering.