Why lithium cells need respect
Rechargeable lithium-based batteries, including lithium-ion and lithium polymer types, are common in phones, tools, drones and hobby electronics because they store a lot of energy in a small package. That same energy is the concern. If a cell is damaged, overcharged, short-circuited or overheated, it can heat up quickly, vent hot gas and sometimes catch fire. Such fires can be intense, can restart after appearing to be out, and are hard to extinguish with a household extinguisher.
Failures are uncommon when cells are used within their design limits, but outcomes are uncertain and the consequences can be serious, so cautious habits are worthwhile. This article is general information. Always follow the instructions from the battery, charger and device makers, which take priority over anything here.
What can go wrong
The usual causes of trouble are:
- Short circuits. Bare terminals touching metal objects, loose wires or a crushed pack can connect the two sides of the cell directly.
- Overcharging or using the wrong charger. Lithium cells need charging that is designed for their chemistry and voltage.
- Physical damage. Punctures, dents, drops and crushing can damage the internal structure.
- Heat. Charging or storing cells in hot places, such as a car in summer or next to a heater, raises risk.
- Age and wear. Old or worn cells can fail in ways that new ones do not.
- Poor-quality or unmarked cells. Packs with no clear maker information or protection are harder to trust.
Warning signs include swelling or puffing of the pack, a strong or unusual smell, hissing, unusual heat during use or charging, leaking, or a sudden loss of capacity. A swollen or damaged cell should be taken out of use.
Charging habits
- Use the charger designed for that battery or the device it came with. Check that the voltage and cell count match.
- Charge on a hard, non-flammable surface, such as a ceramic tile or metal tray, and away from paper, fabric and clutter.
- Do not charge in a bed, sofa or under a pile of materials.
- Stay nearby and check on the charge from time to time, especially for larger packs or hobby cells. Overnight charging of loose cells while you sleep is something many experienced users avoid.
- Stop charging if the battery becomes unusually hot, swells, or smells strange. If it is safe to do so, unplug it and move away from it; do not try to carry a smoking or burning battery through the house.
- Do not charge a battery that looks damaged.
- Let a battery cool after heavy use before you charge it, and avoid charging in the cold, which can harm lithium cells.
Storage
Good battery storage is mostly about keeping cells in a stable condition and keeping fire from spreading if one fails.
- Store at moderate temperature and away from direct sun, heaters and humid or damp spots.
- Keep batteries separate from flammable materials such as solvents, paper, packing foam and sawdust.
- Protect terminals. Keep cells in their cases or use caps or non-conductive covers, and avoid loose cells rolling around in a drawer with coins, screws or tools.
- Store in a container designed for the purpose, such as a fire-resistant battery bag or metal box, if you keep many or large packs. These can slow the spread of a failure but do not make it safe, and no container is guaranteed.
- Keep them where children and pets cannot reach them. Small button cells are especially dangerous if swallowed.
- For long storage, manufacturers often advise a partial charge rather than full or empty. Check what the maker recommends for your type.
- Inspect stored packs now and then. Remove any that have swelled or developed damage.
Do not store a large collection of cells in the only exit route or next to the door. If something does happen, you want to be able to leave and keep the way clear.
Handling and projects
- Avoid using bare cells in your projects unless you understand what protection circuits are needed. A protected pack or module designed for hobby use, with the right connectors, is generally a safer starting point. Low-voltage battery projects remain the most sensible way to learn electronics.
- Do not solder directly to cells unless you have proper instructions, since heat can damage them.
- Use insulated, correctly sized wiring, and secure packs so they cannot move, rub or be punctured in a project.
- Fuse or protect circuits where the design calls for it, and check the maximum current rating of your wiring and connectors. Understanding voltage and current helps you see why a short circuit is so dangerous.
- Tell yourself that a battery is never “dead”. A discharged cell can still start a fire if mishandled.
- Do not mix old and new cells or different types in one pack.
If something goes wrong
Plans differ with the situation, and professional advice should take priority. As a general approach:
- If a battery is hot, swelling or smoking and you can safely get to it without risk, move away from flammable things or let it cool outdoors on a non-flammable surface. If you cannot do this safely, leave.
- If a fire starts, do not try to fight a large or fast-growing one. Get out, close doors behind you and call emergency services. Mention that it involves lithium batteries.
- A small, early fire may be handled using the extinguisher type recommended for it by the fire service or manufacturer. Because advice differs, it is worth asking your local fire service what they recommend.
- Afterwards, remember that cells can reignite. Keep the damaged battery outside, in a non-flammable container, until it can be properly collected.
Transport and disposal
Take extra care when traveling. Airlines and carriers have rules about lithium batteries, and the rules differ by place, so check before shipping or flying with them. Never put damaged cells in the post.
Do not throw lithium batteries in the household trash or recycling. Waste trucks and sorting plants have had fires from them. Take them to a battery recycling drop-off, retailer collection point or hazardous waste facility. Tape over the terminals or place each in its own bag first, as the local scheme advises.
The simple version
Use the right charger, charge where a fire would not spread, store cells cool and covered, replace anything damaged or swollen, and never assume that a small battery is a small risk. Keep a working smoke alarm nearby, and think about where you would go if something started. In a workshop full of other fuel sources, a cautious battery habit is among the most worthwhile you can build.