Charging a rechargeable coin cell is straightforward, but there are a few rules worth getting right — both so the cell lasts and so you stay safe. Here's how to do it properly.
Before you start: check what you're holding
Look at the marking on the cell. It must begin with LIR (or otherwise be clearly marked as rechargeable). A cell marked CR is single-use.
Never attempt to charge a CR2032 or any other single-use cell. They aren't built to accept current, and charging them risks leaking, venting, rupture or fire. This is the one rule with no exceptions.
What you need
- One or more LIR2032 rechargeable cells
- A charger designed for LIR rechargeable coin cells — not a charger for AA/AAA cells, and not a bench power supply
- A USB power source (a phone charger or computer port is fine)
Coin cell chargers are typically a small clamp or cradle that holds the cell between two contacts, with a USB or USB-C input.
Step by step
- Inspect the cell. It should be flat, clean and undamaged. If it's swollen, dented, discoloured, leaking or has any residue on it, do not charge it — recycle it instead.
- Seat the cell the right way round. Polarity matters. The flat, wider face with the printed markings is the positive (+) side; the smaller, slightly domed face is negative (−). Match these to the markings on the charger. A cell put in backwards generally won't charge, and forcing it can damage the charger contacts.
- Make sure it's held firmly but not crushed. The contacts need to touch the faces cleanly. The cell shouldn't be under so much pressure that the casing deforms.
- Connect the charger to USB power. On the TagCharge charger the indicator shows green when the charger has power, and turns red once it starts charging a cell.
- Wait for the indicator to turn back to green. Green with a cell fitted means charging is complete. Coin cells hold a small amount of energy compared with larger batteries, so they don't take long.
- Remove the cell once it's done and fit it to your device, or store it (see below).
Quick reference — green: powered up, or finished charging. Red: charging in progress.
Safety while charging
- Charge on a hard, non-flammable surface — not on a bed, sofa, carpet or pile of paper.
- Don't leave cells charging unattended for long stretches, and don't leave them on charge overnight or for days on end.
- Keep charging cells well out of reach of children and pets.
- Don't charge in direct sun, in a hot car, or anywhere it can't shed heat.
- If a cell becomes noticeably hot, swells, smells, or the charger behaves oddly, disconnect the power and let it cool somewhere safe before handling.
- Charge only one type of cell at a time, and never mix rechargeable and single-use cells in a charger.
Getting the most life out of your cells
- Top up before use rather than long before. Rechargeable lithium-ion cells lose some charge just sitting there, faster than a single-use cell does.
- Don't run them completely flat repeatedly if you can avoid it. Recharging when the device starts misbehaving is kinder than leaving a dead cell in place for weeks.
- Store partly charged, not empty. Somewhere cool and dry, away from metal objects like keys and coins that could short the terminals.
- Keep spares in their packaging until needed — it keeps the warnings with the cell and prevents accidental shorting.
- Expect gradual capacity loss over time. That's normal for any rechargeable cell, not a fault.
A word on battery level readings
If your device shows a battery percentage, it may read strangely with a rechargeable cell. Devices with a battery gauge are generally calibrated around single-use cells, so a rechargeable can read inaccurately, or drop off more abruptly than you'd expect. The cell is usually fine — the gauge just isn't built for it.
Disposal and recycling
Never put lithium cells in your household rubbish or kerbside recycling bin — damaged lithium batteries are a genuine fire risk in waste trucks and sorting facilities.
In Australia, take used batteries to a B-cycle drop-off point. Many supermarkets, hardware stores and council facilities host collection bins. Taping over the faces of a used coin cell with clear sticky tape before you drop it off is a simple way to prevent it shorting against other batteries on the way there.
Safety reminder
Coin batteries are hazardous if swallowed and can cause severe internal injury or death, particularly to young children. Store them out of reach, keep them in child-resistant packaging until use, and dispose of used cells straight away. If a battery is swallowed, seek immediate medical attention or call the Poisons Information Centre on 13 11 26.