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Old 05-10-2017, 11:36 PM   #15
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Originally Posted by pcskier View Post
Inverter is likely 1000 watts, but even if only 500 watts will be no problem. Heated blankets/pads draw as little as 100 watts. Times two sides for a larger one that's 200 watts. And many people keep them set at level 5 out of 10. That's 100 watts total which is .83 amps. 10 hours would draw as little as 8 amps, or as many as 16 if it's pulling 200 watts. Two fully charged, healthy Interstate 24 Batteries provide 84 amps before depleting to 50%. Plenty of power for an electric blanky off the inverter for the night.
That's not correct at all. AC amps don't equal DC amps. (amps x volts = watts).

You're using 12 volts to create that 100 watts via the inverter (also remember your inverter isn't 100% efficient...it uses power to "make" power). Your inverter uses roughly 10 amps DC to make that 100 watts AC. Running that alone for a night will SERIOUSLY deplete your battery bank, assuming you start at 100% charge and use nothing else power wise. (The math looks something like this: to get 100 watts AC from 12v DC and assuming 85% inverter efficiency...100 divided by 12 divided by .85 = 9.8 amps; 100/12/.85=9.8; watts/volts=amps less the loss of power while inverting it.)

I stand by my original statement.
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Old 05-11-2017, 12:48 AM   #16
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Originally Posted by quietguy View Post
That's not correct at all. AC amps don't equal DC amps. (amps x volts = watts).

You're using 12 volts to create that 100 watts via the inverter (also remember your inverter isn't 100% efficient...it uses power to "make" power). Your inverter uses roughly 10 amps DC to make that 100 watts AC. Running that alone for a night will SERIOUSLY deplete your battery bank, assuming you start at 100% charge and use nothing else power wise. (The math looks something like this: to get 100 watts AC from 12v DC and assuming 85% inverter efficiency...100 divided by 12 divided by .85 = 9.8 amps; 100/12/.85=9.8; watts/volts=amps less the loss of power while inverting it.)

I stand by my original statement.
Now once you understand the above you'll understand two more things:

1.) why your two 55 watt low beam headlamps will drain your car battery in just a few hours.

and

2.) why it was so important not to sleep through my physics classes back when you were in high school...




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Old 05-11-2017, 07:24 AM   #17
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We have the Electrowarmth RV queen, 120V AC mattress pad. In the instructions it specifies that you must use a pure sine wave inverter, if powering it from a 12V system. I bought a 300W Samlex pure sine wave inverter to power it when we are boondocking. For now, the inverter plugs into a Blue Sea 12V outlet connected to 10ga marine duplex that I ran to the back bedroom.

We normally just turn it on to warm up the bed if it is cold, but have also left it on low during the night without depleting our 2 6V batteries too much. It does not run constantly, but cycles on and off.

In our truck camper, we have the Electrowarmth 12V version for a twin bed. I sometimes wonder if I shouldn't have put the same thing in the center of our AS's queen bed just to warm it up, thus eliminating the inverter.

I first heard of using heated mattress pads on Handybob's Solar site. He said he has used them for years off an inverter without depleting his batteries.
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Old 05-11-2017, 07:40 AM   #18
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Having worked for a large well known safety certification laboratory I would not use this with an inverter if the labeling says it is not recommended.

Also, if something bad were to happen Insurance may not cover you because the device was used in a manner the documentation indicated was inappropriate.
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Old 05-11-2017, 07:57 AM   #19
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You can perhaps avoid all of these machinations by going non-electric for your warmth..i.e. Down comforters and microfleece.

Maggie
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Old 05-11-2017, 08:46 AM   #20
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We have an electric mattress pad, but only run it when we're plugged in. However, I also do wilderness camping, and use an air mattress. I have found it to be cold (outside air temp is the temp under you). I have started packing a piece of polar fleece to use under the sleeping bag on top of the mattress, and it works wonderfully. Might be an option for you instead of an electric mattress pad. Might be an option for me too.....

Kay
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Old 05-11-2017, 09:46 AM   #21
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We love our mattress pad, but sometimes it is not convenient to use it. We have refelctix under the mattress, flannel sheets and an Eddie Bauer down comforter. The wife will sometimes add a down blanket. i think this is more because she likes the fleece underside more than anything else.
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Old 05-11-2017, 09:11 PM   #22
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Yes it works fine on "shore power ".
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Old 06-09-2017, 10:08 PM   #23
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I use a electric blanket on bed during winter mainly to pre-warm the sheets etc so it will only run for 10 or so mins and then turn off.. With a good down comforter on top unless it like minus zero outside with NO heat you should be nice and warm.

I just leave the furnace on like 55 so it only comes on if real cold. when boondocking and real cold might leave the catalytic heater on low and the vent cracked open as well.

how do the 12v powered unit work?.. I see them at truck stops and have wondered if worth the money. seems like they draw 55 w 4.5 amps but that is a 42 x 53 size. like a twin bed.
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