Energy Consumption (Wh)
The total energy a system uses over a given period; in watt-hours it is found by multiplying voltage, current and hours. An arrangement drawing an average of 8 A at 24 V uses 192 Wh per hour. This calculation determines the operating time in battery sizing and in solar-powered field applications.
Do not forget that in motor applications the current is not continuous. If a barrier opens and closes 200 times a day and each movement takes 4 seconds, the total running time is about 27 minutes; what really matters is the energy drawn during that time.
- Duty cycle: Calculate the average current from the ratio of movement time to total time, not from the peak current.
- Standby consumption: The board draws a small current even when nothing is moving. In a system that sits idle 23.5 hours a day this item can be a significant share of the total.
- Battery margin: In lead-acid batteries, treat roughly half the capacity as usable in order to preserve life; a 100 Ah battery at 12 V means about 600 Wh of usable energy.
In solar-powered installations the panel must be able to cover the daily consumption at the shortest sunshine period of the year; systems sized on summer figures fall short in winter.
The context in which this term is used: DC Motor Driver Selection Guide