## Battery Life Calculator

 C = Capacity rating of battery milliamp hours (mAh) Sa = Current of the device when sleeping milliamps Wa = 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 msph = 3,600,000 how many milliseconds are in an hour Wtph = Wph*Wt wake time per hour Stph = msph-Wtph sleep time per hour mAavg = ((Wa*Wtph)+(Sa*Stph)) / msph average mA of device days = (c/mAavg)/24 life of battery, expressed in days years = days/365 life of battery, expressed in years
 Capacity rating of battery (mAh) mAh = milli-Amp-hours Current consumption of device during sleep (mA) mA = milli-Amps Current consumption of device during wake (mA) mA = milli-Amps Number of wakeups per hour If always on, enter 3600 here. Duration of wake time (ms) ms = milli-Seconds. If always on, enter 1000 here.

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)