Battery Run Time
Battery Run Time
A battery’s run time follows from its charge capacity divided by the current drawn — the basis of every device-life estimate.
The run time is t = Q_bat/I. where Q_bat is the battery capacity and I the load current.
Inputs
Q_bat := 5 A·h=18000 C
I := 0.5 A=0.5 A
Divide capacity by current.
t := Q_bat/I=36000 s
Results
Higher loads drain the battery faster. Real capacity falls at high discharge rates (Peukert effect), so this is an optimistic estimate.
Assumptions & limitations
- Constant current draw.
- Rated capacity at this rate.
- Ignores Peukert/temperature effects.