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Old 02-19-2013, 06:50 AM   #1
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12vt to 110vt

Ok Guys this is a little of topic for a RV but I think this is a good place to post this question.

I need to convert 12vt battery power to run a 110vt fan,pump,and a solenoid.
This is a need for heat when power goes out.
I am completely STUPID when it comes to this type of stuff so can someone direct me to a link that would help me figure this out.

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Old 02-19-2013, 07:00 AM   #2
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This is the function of an inverter. Be aware however, if you are looking to run an electric heat source, batteries will not last long powering a resistant heater.

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Old 02-19-2013, 07:09 AM   #3
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This is not to run resistant heat,I already have the heat just need to move it (wood boiler)
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Old 02-19-2013, 07:12 AM   #4
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First off you need to determine exactly how many amps of 120VAC power you need and for how long. Then, convert that to 12VDC. For every anp of 120VAC power you will need approx 20 amps of 12VDC. That is because you should never discharge a battery beyone 50%. The direct conversion is 1 amp of 120VAC equals 10 amps of 12VDC. Things like fans and water pumps can drain a battery in a big hurry, so to power them for even a short time is going to require a very large system. Personally i think you would be better off adding a generator and auto transfer switch to your system. This system could be matched to items you must have or the whole house your choice qnd budget
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Old 02-19-2013, 08:17 AM   #5
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You need an inverter rated for the load, which will be expressed in watts, e.g. 2000 watts. You need to look at the rating plates on that fan and pump to see how many watts they draw and then add maybe 25% or so for a safety margin (and because you will likely discover other things you want to run at the same time, e.g. phone charger, computer, etc.). You can get an inverter-only, or an inverter combined with a battery charger and internal transfer switch. The latter allows you to power the pump system via the inverter all the time, using pass-thru 120v power as long as it is available but automatically switching over to inverter/battery power when shore power fails.

Then you need to figure out the size battery bank you need to power the inverter. The inverter draws about 10% more power from the batteries than the 120v power it produces, so if you need 1200 watts to run the equipment, figure 1320 watts from the batteries. A watt is amps x volts, so 1320 watts @ 12v means 110 amps will be pulled from the batteries continuously. The final step is to estimate the time you need to run from batteries. If that 92 amps is needed for an hour, that is theoretically 110 amp-hours of battery storage. However, you cannot use more than about 50% of the battery capacity without causing long term damage to it, so best to double the amp hours when buying and installing batteries. That would be 220 amp-hours (AH) in this example. A pair of 6V golf cart deep cycle batteries can store 225 AH, so you would need about two batteries for each hour your heating system may need to run (assuming the 1200 watt figure in this example).

As you can see, any substantial power load requires a lot of battery storage, so often a stand-by generator is a better choice for emergency power.
Gary Brinck
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Old 02-19-2013, 09:04 AM   #6
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Thanks guys,
Sounds like should just get a smaller generator to power the fan and 1/25hp pump.
I do have a 20KW generator now but it sucks a lot of propane so a smaller generator with less fule usage may be inorder.
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Old 02-19-2013, 09:12 AM   #7
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Thanks guys,
I guess a smaller generator is what I need.
I do have a 20KW generator now but it uses to much fuel for just a fan and 1/25hp pump.
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Old 02-19-2013, 10:47 AM   #8
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Get 12 volt devices and call it a day
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Old 02-19-2013, 05:45 PM   #9
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TQ60, that is what I was thinking reading the replies, until I reached yours saying the same thing. Both the fan and small water pump may be purchased in 12VDC or 12VAC; plus, changing them out to 12V would eliminate the considerable expense of a large inverter, not to mention the huge,heavy battery bank to power the inverter; then always be worrying if the battery bank would last until shore power was restored.
2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert theConstitution. "Abraham Lincoln"
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Old 02-19-2013, 06:43 PM   #10
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Out of curiosity is this for an RV or are you working on a home or cabin or off grid set up?

Bob, Sandi & Marmaduke the Big Pug
SW OREGON 2004 Journey 39K, 330 Cat
If towing: a 2006 Mini Cooper or 1995 Wrangler
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