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Old 07-07-2010, 10:26 PM
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Harvey Harvey is offline
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Join Date: Jul 2009
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Is Ok For Current MOSFET

Hi Glen,

At 1000W, we are still well within the voltage and amperage limits of the IRFPG50 on that element because the Amperage would only be about 4.2A. That is the advantage of using the 240V

The problem, in a battery powered system, is to boost the battery voltage to 240V in a 1kW configuration. Of course the simple answer would be 20 batteries in series and that is not all that far-fetched in real world applications I have seen.

However, a 1kW Inverter could be used as well but such approaches inevitably add unwanted losses to the system.

Another approach would be to use a voltage multiplier front end that typically has lower losses associated with it compared to the inverters. Of course a single 700Ah car battery would only give you about 8 hours of operation before needing to be recharged if it were feeding a 1kW heater.

I installed a 120VAC Hott Rod heater in my Dads hotwater heater in his RV and that was a very easy thing. It does not run continuously because after the 6 gallons are heated up it only has to maintain it (unless of course you bath and then the process must repeat). It takes his about 20 minutes to heat up to 125F from a cold start of about 65F water temp. They advertise 45-90 minutes but I don't know if that is in cold weather or what. So, what ever the calories to do that heating of 6 gallons in that time period gives an idea of the energy used. He has a 2kW inverter that he uses to run that when he is remote but I think it is about 400W that it uses. I've heard of people in the outback running these strictly off of solar energy. I installed 3 solar panels on his rig, but they are only 15W each so it takes about 3 hours of sunshine on his system to get a single 6 gallon heating based on 400W * 20 minutes = 8,000W minutes. So 8,000W minutes divided by the 45W solar recharge gives just under 3 hours. He uses the rest of the recharge time to prep for TV watching etc. at night. He rarely uses the generator or engine to recharge anymore - but he does need those for AC or Microwave use.

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