I was asked to determine what the average power consumption of a system throughout a specific time period. The system runs off a battery, which, according to them, was fully charged (PN: RRC2040-2). They measured 12.44 V initially and let the system run for four hours. After four hours have passed, they measured the battery again and got 10.10V. I was then asked to calculate the average power consumption throughout that time period.

I've been pondering this for a couple hours and I'm stuck.

I understand that:

Energy = Power x Time

Battery Capacity (Coloumbs) = Current x Time

Power = Voltage x Current

Looking at the following equations and their derivations, I end up getting an unreasonable average current draw from my experience testing with the circuit cards or getting stuck in determining the average power draw. Is it not possible to get an estimated average power consumption from the values that were provided to me?

Any advice or input of what I might be missing to solve this would greatly be appreciated.


  • \$\begingroup\$ that would depend on the health of the battery \$\endgroup\$
    – jsotola
    Oct 4, 2023 at 22:38
  • 1
    \$\begingroup\$ you don't even need math here. You used up all the watt-hours of the battery. At 10v, there's nothing usable left, and it was full. Therefore, all you need to is know the WH of the battery, which is AH*12. \$\endgroup\$
    – dandavis
    Oct 4, 2023 at 22:50

1 Answer 1


try and figure out what the load is and go thru V^2/R to get an idea of power consumed and then go and try P=V*I to get I

  • \$\begingroup\$ This is a suggestion, not an answer. Edit it in accordance to EE rules, otherwise it will be removed. \$\endgroup\$
    – MiNiMe
    Oct 5, 2023 at 5:31

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