Symptoms
- Batteries show full charge but die quickly in use
- Device shows low battery soon after a fresh charge
- Charger indicator finishes quickly, faster than it used to
- Problem affects all batteries of one age or brand, not just one
Likely causes
- CommonBattery cells have reached end of lifeNiMH and lithium rechargeables typically hold a noticeably weaker charge after 300–500 cycles.
- PossibleCharger is faulty or mismatched to the battery typeUsing the wrong charger can undercharge or damage rechargeable cells over time.
- PossibleBattery was stored fully depleted for a long timeDeep discharge storage can permanently reduce capacity, especially for NiMH cells.
- Less commonDevice itself is drawing excess powerA malfunctioning device can drain even good batteries fast.
What to do
- Confirm the charger matches the battery chemistry (NiMH, NiCd, or lithium) printed on the batteries.
- Fully charge the batteries, then test them in a different, known-good device to isolate the cause.
- If they still drain fast in a different device, the batteries themselves are worn out.
- If they work fine elsewhere, the original device may be drawing too much current or have a fault.
- Cycle older NiMH batteries through a full charge/discharge once, since sitting unused for months can cause a temporary capacity drop.
- Replace batteries that are more than 2–3 years old or show a clear, permanent drop in runtime.
Tools and parts
- Battery charger matched to battery type
- Second test device (optional)
Rechargeable AA/AAA batteriesSearch: “rechargeable NiMH batteries”
When to call a pro
No professional service applies here; replace worn rechargeable batteries rather than repairing them.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.