🔋 Battery Self-Discharge
Ever changed a re-chargeable battery with one you know is charged only to find it to be nearly dead? I have!
I keep a small box of rechargeable batteries, various sizes and chemistry, all ready to go. Batteries only ever get put in the box once they are charged. The trouble is that batteries self-discharge. For primary cells (aka non-rechargeable) the process happens over many years, for re-chargeable cells it's a whole different story:
| Chemistry | Monthly discharge rate | Time to 50% capacity |
|---|---|---|
| Lithium-ion | 2-3% | ~23-28 months |
| Lithium-polymer | 5% | ~14 months |
| NiMH (Conventional) | 30% | ~2 months |
| NiMH (Low self-discharge) | 0.25% | ~23 years |
| Lead-acid | 4-6% | ~11-17 months |
This is why every couple of months I get out all my NiMh cells and charge them.