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Running Air conditioner on the 12 volt system


ken sanders

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I have a 1989 Sunrader that has #4, 6 volt deep cell batteries that are connected in series and parallel. My cabin mechanic says I should be able to run the air conditioner off the 12 volt batteries for maybe up to 40 minutes. I’d like to run it of the system for about 10 minutes just to cool the cabin before going to bed. I have an inverter, but am unsure if I have to plug the AC into a socket that’s connected to the 12 volt/inverter system, or if it should automatically come on when disconnected from land line 120v service. I haven’t been able to contact my cabin mechanic lately. 

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Before a valid answer, we need to know what brand and model of inverter.

Does it have a built in transfer switch?

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Even the really big stuff tried that ideal and gave up. Ok 17 amps AC at 120 volts = 170 amps at 12 volts DC to drive the inverter cable loss and and inverter efficiency would probably be more like 190 amps DC. You would need some type of transfer switch because the coach AC is hardwired or plug the coach cable into the inverter. Either way it's not sustainable and how do you intend to recharge the batteries after they have been drawn down that hard? Your inverter would be maxed out at 17 amps (120VX17A=2040 watts).

Edited by Maineah
because I can
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Good news, bad news. You can do it, but your are going to spend $$ to do it.

Assumptions you have 4 t-105 or GC-2 batteries. Thats 450AH. Safety discharge means 225AH of usable power so your house mechanic is consertive on his time numbers.

You have a typical 13.5k BTU roof AC. SO your looking at 1400w running and 5000w to start. So you going to need a bigger inverter. Also some serious battery cables. Your start up current will be drawing 450 amps from the batteries

Stuff you need

A 30 amp ATS will run $60.

Plan B something like a Xantrex Freedom X-3000 inverter. It is a pure sine and can deliver 6000w for 2 sec, it also has a built in transfer switch. $850.00

Options

A new generation smaller AC will draw less power and increase run time and reduce start up power needs. But thats even more $$. Like 1100w running  $600

UBI the 11K Colman will run off a Honda 2200w generator. $1000.00, but then you have power when you need. Like a microwave.

 

 

Edited by WME
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If you really want to be cool invest in a 2200 watt Honda or better yet a Yamaha 2400 for a touch more it will work and not run you broke with doodads and batteries to maintain. Personally I run solar and a Fantastic fan.

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OK here is a new idea.

ATS  $60

Easy Start $300...https://www.microair.net/collections/easystart-soft-starters/products/easystart-364-3-ton-single-phase-soft-starter-for-air-conditioners?gclid=EAIaIQobChMIw5rA1eDL5AIVAR-tBh348QENEAQYASABEgJqFfD_BwE&variant=30176048267

The outboard ATS will take the power from your exhisting inverter and direct it to the 115v ac house power panel.

The easy start will reduce the start up surge from your Roof AC from 42 amps to something around 16 amps. Your 2000w inverter should be able to handle that. I don't know how happy the AC will be running on a modified sine wave.

Ya pays ur money, an makes ur choices.

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  • 4 weeks later...

I just bought and installed a soft start kit in my Coleman roof air unit on my 1987 Sunland Express. I purchased this kit on an ebay auction from applianceandair and it is the best $100. i ever spent! I have a small 2500 start 2000 run generator bolted to the back bumper and it wouldn't start the ac before, but will now! Installation was a breeze. Take the top cover off(4 screws) . Remove the cover where all the wires go. Select the black wire and the white wire running to the fan, cut the wirenuts off and hook in the soft start as directed! Took about 1 hour start to finish( I'm old and slow)

In use, there will be a slight delay when you turn the ac on. Then you will hear the ac compressor start on the roof,  then you will hear the generator pull down and the fan comes on and the ac starts! I was amazed!!! An electrician friend told me he doubted it would work and came by as I was installing it. He too was amazed that small generator could start and run the ac!!!!

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