# How long would the battery last



## artona (Jan 19, 2006)

Hi

If amps = watts/volts (is that right ?) then am I right in thinking a 240volt unit that draws 1000 watts would drain 4 amps per hour.

Using an invertor would we then get approx 32.5 hours from a 130 amp/hour battery?

stew


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## teifiprt (Oct 2, 2007)

You're drawing 4 amps at 240v, correct. BUT the inverter supply is only 12v. You will get nowhere near 32 hours, considerably less, sorry.
Peter.


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## Jezport (Jun 19, 2008)

No because you are pulling 1000watts from 12volts which will use about 83A at a guess + about 10 to 20% more for the inverter. Thats before you work out how much drain you could take out the battery before the inverter switches it self off at low voltage.


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## GEMMY (Jun 19, 2006)

You wish. :lol: :lol: :lol: 

tony


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## Manchego (Sep 26, 2009)

That can't be right, can it ?. My little 350W sterling inverter flattens my batteries in about 4 hours. Do i need new batteries ?.


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## JeanLuc (Jan 13, 2007)

Sorry to disappoint you but when you are using an inverter, the power (watts) has to be supported by the much lower input potential (12 volts).

So the calculation is 1,000 / 12 = 83.3 amps. Then allow for inefficiency in the inverter (say 85% efficient) so 83.3 / 0.85 = 98 amps.

Given that you don't want to exhaust your battery completely, that means 1 hour from a 130 Ah battery would have discharged it by 75%. Probably about the limit for practical use.

Philip


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## artona (Jan 19, 2006)

Thanks, back to the gas


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## DABurleigh (May 9, 2005)

And I guarantee a kw from a single 12V lead acid leisure battery would shut the inverter down after 10-15 minutes rather than even lasting anything like an hour, courtesy of Peukert.

Dave


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## teensvan (May 9, 2005)

That type of draw current from a leisure battery would also buckle the plates after a very short time. Most leisure batteries are designed to give a low amp output over a long time. 

steve & ann. --------- teensvan


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