Ninehigh
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| posted on 2/5/13 at 01:30 PM |
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Quick electrical Q
If I have a device rated at 0.7w (lets say for the purposed of this it's using the 0.7w all the time) and a battery that delivers 200mah at 9v,
how long will that battery last?
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tegwin
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| posted on 2/5/13 at 01:52 PM |
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So the device needs 0.077A (given that A=W/v)
And the battery provides 0.2amp hours.
You can run the battery for about 2.6 hours... Although in reality the time would be less as it is not a linear scale
[Edited on 2/5/13 by tegwin]
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MikeRJ
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| posted on 2/5/13 at 01:53 PM |
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Current drawn for 0.7W at 9v = 0.7/9 = 78mA
200/78 = 2.5 hours.
This is assuming the device is powered directly from the 9v battery, no regulators etc.
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Ninehigh
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| posted on 2/5/13 at 01:55 PM |
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Actually that sounds about right.
Thankyou both
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