Lead acid | Nickel metal hydride | Lithium ion | |
---|---|---|---|
Specific energy | 20-35 Wh/kg | ~65 Wh/kg | 90 Wh/kg |
Energy density | 54-95 Wh/L | ~150 Wh/L | 153 Wh/L |
Specific power | ~250 W/kg | 200 W/kg | 300 W/kg |
Nominal cell voltage | 2 V | 1.2 V | 3.5 V |
Internal resistance | ~.022Ω per cell | ~.06Ω per cell | ~.2Ω per cell |
Self-discharge | ~2% a day | ~5% a day | ~10% a month |
Recharge time | 8h (90% in 1h possible) | 1h (60% in 20min possible) | 2-3h |