How to Store Cordless Tool Batteries
Lithium-ion tool batteries do not die from use as much as from neglect: left empty for months, baked in a truck or frozen in a garage. A few storage habits add years to an expensive pack.
How to store power tool batteries: keep them cool, dry and indoors, out of direct sun, off the charger and never fully empty. For storage of weeks or months, a partial charge is the general lithium-ion recommendation, though some brands (DeWalt, for example) say to store packs fully charged, so follow your manual. Avoid hot vehicles and sheds; DeWalt warns against places that reach 104°F, and Milwaukee against 120°F. Recycle damaged packs through Call2Recycle or a local hazardous waste site.
On this page
How to store power tool batteries: the short rules
These rules come from tool manufacturers' manuals and general lithium-ion battery guidance. Your own battery and charger manuals take priority if they differ.
| Rule | Why | Source |
|---|---|---|
| Store cool and dry, away from direct sun | Heat speeds up permanent capacity loss | DeWalt and Milwaukee manuals |
| Avoid hot vehicles, sheds and metal buildings in summer | DeWalt warns against places that may reach 104°F (40°C); Milwaukee against 120°F (50°C) | DeWalt and Milwaukee manuals |
| Never store a pack completely empty | A deeply drained pack may lock out and refuse to charge | DeWalt manuals; general Li-ion guidance |
| Store out of the charger for long periods | Recommended for optimal results | DeWalt manuals |
| Charge level for long storage | Partial charge reduces aging; some brands say full | Check your manual |
| Warm a cold pack before charging | Charging when very cold can damage cells; chargers delay it | Charger manuals |
What charge level is best for storage?
This is where advice conflicts, so here is the honest version. General lithium-ion research and many battery makers say cells age more slowly when stored partly charged, often quoted as roughly 40 to 60 percent, than when held at 100 percent for months. That is why many devices ship half charged.
Tool brands are not uniform. DeWalt's manuals say that for long storage, a fully charged pack stored in a cool, dry place out of the charger gives optimal results, and that packs should not be stored completely depleted. Other brands publish different guidance. The common ground is clear:
- Never store a pack empty. This is the most damaging habit and the one every source agrees on.
- Do not leave packs at full charge in a hot place. Heat plus high charge is the worst combination.
- For a season of storage, leave packs with two or three bars on the fuel gauge, or follow your brand's manual if it says otherwise, and check them every few months.
For day-to-day use, do not overthink it. Charging after use and putting the pack on a shelf is fine.
Lithium battery storage in the cold and the heat
Cold garages and trucks
Cold itself is not very harmful to a stored lithium-ion pack. Problems come from using and charging it cold. A frozen pack delivers less power and may cut out, which can look like a dead tool (see impact driver won't turn on). Charging a very cold pack can damage the cells, which is why most brand chargers delay charging until the pack warms up. In winter, bring packs indoors overnight, or at least let them reach room temperature before you charge them.
Hot vehicles and sheds
Heat is the real enemy. A truck cab or a metal shed in summer can get far hotter than the outdoor air. DeWalt's manuals specifically warn against outside sheds and metal buildings in summer, and Milwaukee's charger manual names vehicles and direct sunlight. Carry packs in the cab with you rather than in a closed toolbox in the sun, and never leave them on a dashboard.
Job sites
On site, keep spare packs in the shade, in an insulated bag or a cooler without ice in summer, and inside the heated building in winter. Rotate packs so each one gets used and recharged regularly rather than leaving one at the bottom of a bag for months. A pack that comes off the tool hot should cool for a while before it goes on the charger; most chargers will wait anyway.
Long-term storage checklist
- Charge or discharge each pack to your brand's recommended storage level, and never leave one empty.
- Remove packs from tools and chargers.
- Fit terminal covers if you have them, or keep packs where nothing metal can touch the terminals.
- Store indoors in a cool, dry place, off concrete floors that sweat and away from heaters and windows.
- Keep packs away from flammable materials such as fuel cans, solvents and rags.
- Check the fuel gauge every few months and top up any pack that has dropped low.
- Before use, let packs reach room temperature, then charge fully.
For battery types and sizes, see our impact driver battery guide, or the brand-specific Milwaukee M18 and DeWalt 20V battery guides.
Signs a battery should be retired
| Sign | What to do |
|---|---|
| Swollen, bulging or cracked case | Stop using immediately; isolate and recycle as damaged |
| Gets hot without use, hisses or smells of solvent | Move outdoors away from anything flammable if safe; do not charge |
| Leaking or corroded terminals | Stop using; recycle |
| Charger shows a defective-pack fault | Check warranty, then recycle. See battery not charging |
| Runtime far below normal | Worn cells; fine for light use or recycle |
| Dropped hard or soaked | Inspect; if any damage, retire it |
Do not open packs, replace cells yourself or use non-brand chargers and battery adapters to revive a pack that the brand charger rejects. Protection circuits exist for a reason.
Recycling and damaged-pack disposal
Never put lithium-ion tool batteries in household trash or curbside recycling. They can start fires in trucks and sorting facilities.
- Undamaged packs: Call2Recycle runs drop-off locations across the US, including many home improvement stores. Tape the terminals or put each pack in its own plastic bag first to prevent short circuits.
- Damaged, swollen or recalled packs: Call2Recycle's guidance says not to place damaged lithium-ion batteries in a standard collection box. Put the pack in a non-flammable material such as sand or cat litter in a cool, dry place, then contact Call2Recycle's damaged, defective and recalled battery program or your local household hazardous waste facility for instructions.
- Under warranty: Contact the manufacturer before disposing of a failed pack. They may need it returned.
Safety: If a battery is smoking or on fire, get people away and call 911. Do not try to handle a burning pack.
For a full tool and battery care routine, see impact driver maintenance.
Frequently asked questions
Can I leave tool batteries in a cold garage?
Storage in a cool garage is fine, and cold storage is gentler on lithium-ion than heat. The problems come when you use or charge a frozen pack. Bring it indoors to room temperature before charging. Most chargers delay charging a pack that is too cold or too hot.
Is it bad to leave a battery on the charger?
Brand chargers stop charging when the pack is full, so leaving it briefly is not dangerous for most systems. For long storage, manufacturers such as DeWalt recommend storing packs out of the charger. Unplugging also avoids leaving electronics powered for months.
How long can a tool battery sit unused?
Lithium-ion packs self-discharge slowly, so a charged pack can sit for months. Check the fuel gauge every few months and top up any pack that is low, because a pack that drains completely may refuse to charge.
Should I store batteries in the tool?
For more than a few days, no. Remove the battery so nothing can drain it, the trigger cannot be pressed accidentally and the contacts stay clean. Store packs with terminal covers on if your brand supplies them.