I've got 15 devices each with a current of 20mA and I am interested in running them all for 10 seconds. How would I go about working out the amount of mAh a battery would need to provide for this?

I understand that to find the mAh to run something for an hour you take the current and multiply it by 1000 and so my understanding of his problem was that you could get minutes by multiplying by 100 and then seconds by 10. So What I thought I needed to do was something like this:

15 x 20mA = 300mA/0.3A

0.3 x 10 = 3

3 x 10(seconds of runtime) = 30mAh

However I am not sure if this is right, so I would be grateful if someone could look it over and point out my mistakes.

  • \$\begingroup\$ Likely this factor of 1000 came from a source showing how to find the Ah rating for a battery if your are given current consumption in mA. 1000mA = 1A \$\endgroup\$ – sherrellbc Mar 24 '15 at 13:18

I = 15 * 20mA = 300mA

t = 10s

x = 300mA * 10s = 3000mAs = 3000mAs/3600s = 0.8(3) mAh

That is a small amount of electric charge.

  • 1
    \$\begingroup\$ This answer is incorrect. It calculates the amount of mAh that needs to be delivered to the device. But the question asked what the mAh of the battery needs to be. For such low discharge times, these two answers will be very different. \$\endgroup\$ – David Schwartz Aug 31 '16 at 17:58

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