In short
Store lithium batteries at partial charge, somewhere cool, dry and stable, clear of combustible materials, with damaged packs kept separately. Check them periodically for swelling and top them back up before they over-discharge. Use the manufacturer’s figures for charge level and temperature rather than a general rule.
The steps below are in the order they matter. Most workplaces get the first three roughly right and the last two not at all.
1. Separate the damaged from the healthy
Before anything else, know which packs are suspect. Swelling, deformation, heat when idle, unusual smell, discoloration, leaking, a sudden drop in capacity, or any pack that has been dropped or crushed — including ones that look fine afterwards. These go to a defined quarantine location, not back on the shelf and not on charge.
Quarantine should be physically separate and, where practicable, outside the occupied building. Once a pack is waste it falls under the Waste Batteries and Accumulators Regulations 2009, so decide who collects it and how often before you have a queue.
2. Set the state of charge
Partial charge, not full and not flat. Full charge accelerates ageing and stores the maximum energy available to be released in a failure; fully discharged risks over-discharge, which damages cells and makes later charging hazardous.
The specific figure belongs to the manufacturer. It varies by chemistry and by product line, and datasheet guidance is more reliable than any percentage repeated on forums. If no figure is available, a mid-range charge is a defensible default — and worth recording as an assumption. More on storage temperature and voltage.
3. Choose the location
- Cool and stable. Not next to heating plant, not in direct sun, not in an uninsulated container or a vehicle.
- Dry. Condensation and water ingress are damage mechanisms in their own right.
- Off the escape route. A store on the way out is the wrong store, whatever is in it.
- Away from sleeping accommodation. This governs hotels, care homes, schools with boarding and residential blocks.
- Accessible to the fire service, and known to them where quantities are significant.
4. Clear the surroundings
A failing pack needs fuel to become a building fire. Cardboard, packaging, pallets, textiles, aerosols and flammable liquids are the usual neighbours in a stockroom, and moving them is free. Physical distance between packs matters too: separation is the cheapest fire break available and costs floor space rather than capital.
5. Decide whether containment is justified
For a handful of healthy packs, a cool separated shelf away from combustibles may be a reasonable control. As total energy content rises — and it rises much faster than pack count suggests — the case for a tested enclosure strengthens. A cabinet contains a failure and buys time; it does not prevent one. See battery cabinets and, if charging is involved, charging cabinets.
6. Set up the periodic check
Stored batteries self-discharge slowly, and a pack left for a year can drift into over-discharge. A recurring check — inspect for swelling and damage, verify charge level, top back up to the storage figure — closes that gap. Six-monthly is a common interval; the manufacturer’s guidance takes precedence, and packs in a warm location need looking at more often.
Put the check in whatever system already carries your other recurring tasks. A storage regime that depends on someone remembering is a storage regime that lapses.
Frequently asked questions
Can lithium batteries be stored in a fridge or freezer?
Don’t. Cold storage introduces condensation when packs come back to room temperature, and a cold pack put straight on charge can be damaged by it. Cool and stable at normal indoor temperatures is what is wanted, not cold.
Should batteries be removed from equipment for storage?
Generally yes for anything stored for more than a few weeks. A pack left in a tool or a bike can discharge slowly through the device’s electronics, and packs stored separately are easier to inspect, separate from one another and quarantine if something looks wrong. Follow the manufacturer’s guidance where it says otherwise.
Can different battery types be stored together?
Physically yes, but you inherit the risk profile of the least tolerant pack present, and mixed storage makes it harder to apply the right charge level to each. Keep terminals from contacting other packs or metal objects — short circuits across loose cells are a real failure route. Where you have both e-bike packs and small tool batteries, separating them by type is usually easier to manage.
Do batteries need to be stored in their original packaging?
Original packaging is helpful because it holds terminals clear and prevents packs contacting each other, and it is normally required for transport. For static storage the substance of it matters more than the box: terminals protected, packs not pressing against each other, nothing combustible packed in with them. Cardboard around every pack works against the “clear the combustibles” step, so use judgement.