Battery Life Calculator
The output of this calculator is an estimate, not a guarantee.
Capacity is automatically derated by 15% to account for some self
discharge.
Other factors such as temperature can extend or shorten the battery
life.
mAHr Capacity of typical
batteries that we're
likely to use:
| AAA | 1200 (Alkaline) 800–1000 (NiMH) |
| AA | 2700 (alkaline) 3000 (Lithium-Rechargeable) 1700–2900 (NiMH) |
| C | 8000 (alkaline) 4500–6000 (NiMH) |
| D | 12000 (alkaline) 2200–12000 (NiMH) 19000 (Lithium-Primary) 3.6V |
| 9V Transistor | 565 (alkaline) 1200 (lithium-Primary) 175–300 (NiMH) |
| 6V Lantern | 26000 (alkaline) |
| CR2032 | 240 (Lithium-Primary) 3.6V |
| CR2016 | 90 (Lithium-Primary) 3.6V |
| 1/10 D | 1000 (Lithium-Primary) 3.6V |
| 4 Farad Cap | 1 (loses 1 volt in 1 hour at 1mA) |
The Basic Formula:
| C = Capacity rating of battery | milliamp hours (mAh) |
| As = Current of the device when sleeping | milliamps |
| Aw = Current of the device when awake | milliamps |
| Wph = Number of wakeups per hour | |
| Wt = Duration of a single wake | milliseconds |
| c = C*0.85 | derated capacity in mAh |
| 3,600,000 | how many milliseconds are in an hour |
| Twph = Wph*Wt | wake time per hour |
| Tsph = msph-Wtph | sleep time per hour |
| Aavg = ((Aw*Twph)+(As*Tsph)) / 3,600,000 | Current on average (milliamps) |
| days = (c/Aavg)/24 | life of battery, expressed in days |
| years = days/365 | life of battery, expressed in years |