Before storage: prep the battery properly
Storage starts with a battery in good shape, not a battery that is already struggling. If the pack is near the end of its life, storage will not save it — but a healthy pack stored well will hold up for months.
- Give it a full charge, then equalize. Charge the battery fully, then run an equalizing charge on the manufacturer's schedule. Equalizing balances the cells so no single weak cell drags the pack down while it sits.
- Check the water level. Top up with distilled water to the correct level — after charging, not before. Plates exposed to air sulfate quickly, so no cell should sit with low water.
- Clean the top. Wipe down the battery top and terminals. Acid film and grime cause slow stray discharge across the top of the battery, which drains it faster in storage.
- Inspect for damage. Look for cracked cases, leaking cells, corroded terminals, and damaged cables. Fix what needs fixing before storage — a small leak becomes a big problem over three idle months.
- Disconnect it. Disconnect the battery from the truck and the charger so nothing draws power while it sits.
- Record the readings. Note the date, the voltage of each cell or the pack total, and the specific gravity. These numbers are your baseline — they tell you how the battery is holding up when you check it later.
During storage: check it on a schedule
A stored lead-acid battery self-discharges. The rate depends on temperature and the battery's condition, but a typical flooded battery loses a noticeable share of its charge every month. The danger is not the discharge itself — it is letting the battery sit discharged long enough for sulfation to harden on the plates. Once sulfation hardens, no amount of charging brings that capacity back.
- Check voltage monthly. Measure per-cell voltage at least once a month. A cell that is falling faster than its neighbors is a warning sign worth investigating before it becomes a dead cell.
- Boost or equalize every 2 to 3 months. When the pack voltage has dropped meaningfully, give it a full charge and an equalizing charge. Do not wait until it is nearly flat — the point is to keep it from ever getting there.
- Keep it cool and dry. Store the battery in a cool, dry, ventilated place, off the floor if possible, away from direct sunlight and sources of heat. Heat speeds up self-discharge; dampness corrodes terminals and connections.
- Keep it clean. Wipe the top periodically. Dust and acid film build up even in storage, and the stray discharge they cause adds up over months.
- Put the schedule on a calendar. Storage checks fail because nobody owns them. Assign the checks to a person and a date, and log the readings every time.
Winter and cold storage
Cold is a mixed blessing for a stored battery. Lower temperatures slow self-discharge, so a battery stored in a cold warehouse loses charge more slowly than one in a warm shop. But cold brings its own risks, and the biggest one is freezing.
A fully charged lead-acid battery resists freezing well — its electrolyte is strong acid, which freezes at a very low temperature. A discharged battery is a different story: as the charge drops, the electrolyte becomes closer to plain water, and it can freeze at temperatures a Michigan winter hits regularly. A frozen battery can crack its case, buckle its plates, and spill acid. That is why storing a battery fully charged matters most in winter.
- Never charge a frozen battery. If you suspect a battery has frozen — bulging case, ice visible, or the pack was stored discharged in sub-freezing temperatures — do not plug it in. Let it thaw fully at room temperature first, then have a dealer inspect it before charging.
- Expect less power in the cold. Even a healthy battery delivers less capacity when cold. A truck coming out of winter storage may run shorter shifts until the battery warms up through use.
- Protect terminals from corrosion. Cold, damp storage accelerates corrosion on terminals and connectors. A light coating of terminal protectant before storage helps.
Returning to service
Bringing a stored battery back is not just a matter of plugging it in and driving. A battery that has sat for months needs a proper recommissioning, and skipping it is how a stored battery dies in its first week back.
- Inspect first. Check the case, terminals, and cables for cracks, corrosion, and leaks. Look for any sign of freezing or damage that appeared during storage.
- Check the water. Top up with distilled water to the correct level before charging if any cell is low.
- Equalize. Run a full charge followed by an equalizing charge. This rebalances cells that drifted apart during storage.
- Test it. Take per-cell voltage and specific gravity readings, and run a load test if the battery sat for a long time or the readings look uneven. A dealer load test takes about an hour and tells you whether the battery is ready for full shifts or needs attention.
- Ease it back in. If the battery has been idle for months, give it a lighter first shift if you can. Watch runtime and charging behavior for the first few cycles before putting it on a heavy schedule.
Lithium storage differences
Lithium-ion batteries store very differently from lead-acid, and the rules are almost the opposite. Do not store a lithium pack fully charged — the manufacturer's guidance is usually a partial charge, often around 40 to 60 percent, which reduces stress on the cells during long idle periods. Check your specific battery's manual for its recommended storage charge level.
Lithium self-discharges far more slowly than lead-acid, so monthly top-ups are generally not needed — but the pack should still be checked periodically, and the battery management system (BMS) keeps the cells balanced on its own. Store lithium in a cool, dry place and keep it away from extreme heat, which degrades lithium cells faster than cold does. Never store a damaged lithium battery indoors, and follow the manufacturer's instructions for any pack that has been dropped, punctured, or exposed to water.
If you are unsure whether your stored battery is still healthy, a dealer inspection is cheaper than a truck that dies mid-shift. For the day-to-day habits that keep a battery healthy between storage periods, see our battery maintenance guide and the technical reference in our specs guide.