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Discuss Calculate device/battery run time in the DIY Electrical Forum area at ElectriciansForums.net

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Hello

I am trying to calculate how long a car battery will last for which is 50ah, 12v. Running a 20watt device, 240v, turned on 24hours a day, how long would this battery last?
Any help appreciated
thanks
 
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telectrix

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20 watts @ 12V =1.667A.

you should get around 24 hours out of the battery. are you using an inverter? that will cause some loss.
 
D

Deleted member 26818

20 watts @ 12V =1.667A.

you should get around 24 hours out of the battery. are you using an inverter? that will cause some loss.
50 Ah divided by 1.667A = just under 30 hours.
 

DPG

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Remember that car batteries should not be flattened completely. You would need a deep cycle battery (aka leisure battery etc).
 
D

Deleted member 26818

I measured some 7Ah batteries at work the other day, they measured 11Ah.
New last year.
 
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