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wanderingbob

monticeeo, fla

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Posted: 07/20/22 12:49pm Link  |  Quote  |  Print  |  Notify Moderator

Assuming that I have the battery power would a 3,000 watt inverter run a rooftop 13,500 air for an hour or so ? I now have 4 six volts hooked up as 12 volts . I would only need air for an hour or so each day . Nothing else on batteries except normal pumps and lites .

BB_TX

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Posted: 07/20/22 01:29pm Link  |  Quote  |  Print  |  Notify Moderator

13.5k A/C draws around 13 amps of 120 vac. That is around 130 amps of 12 vdc. Don’t know what starting amps is but a soft start would help.

Gdetrailer

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Posted: 07/20/22 01:47pm Link  |  Quote  |  Print  |  Notify Moderator

Go with a 3000 watt generator, otherwise you are barking up an expensive tree.

High wattage loads like A/C while can be done via large battery banks for short periods of time, it draws the batteries down at a much faster rate than small low amperage loads. Basically depleting the charge at a much faster rate. It is also hard on the batteries and you need to recharge the batteries very quickly if you hope to have long life from them.

As noted, 13.5K A/C can draw 13A at 120V which is 1560W, but that does not take into account the startup surge which can be as much as 25A at 120V or about 3,000W.. Most cheapo inverters do not have enough surge capability in time they are able to provide the surge power to handle A/C compressor startup..

That 25A at 120V roughly translates to 250A or more at 12V..

Generator is the correct tool for the job.

Lwiddis

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Posted: 07/20/22 01:53pm Link  |  Quote  |  Print  |  Notify Moderator

Running an RV A/C with an inverter and batteries just isn’t practical now IMO.


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wanderingbob

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Posted: 07/20/22 02:58pm Link  |  Quote  |  Print  |  Notify Moderator

I got the generator , I was just curious ! Thanks !

time2roll

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Posted: 07/20/22 03:29pm Link  |  Quote  |  Print  |  Notify Moderator

Yes if the 4x GC2 are fully charged they should drive the A/C for an hour. But not much more. The 1 hour discharge rate will reduce capacity close to 50%. (Peukert effect)

3000w inverter should have no issues. My 2000w will start and run my 16yo Dometic 13.5 BTU A/C same as utility power. Mine will draw 120-130 amps running the A/C.


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Posted: 07/20/22 03:32pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

Yes if the 4x GC2 are fully charged they should drive the A/C for an hour. But not much more. The 1 hour discharge rate will reduce capacity close to 50%.

3000w inverter should have no issues. My 2000w will start and run my 16yo Dometic 13.5 BTU A/C same as utility power. Mine will draw 120-130 amps running the A/C.


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wa8yxm

Davison Michigan (East of Flint)

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Posted: 07/20/22 04:08pm Link  |  Quote  |  Print  |  Notify Moderator

wanderingbob wrote:

Assuming that I have the battery power would a 3,000 watt inverter run a rooftop 13,500 air for an hour or so ? I now have 4 six volts hooked up as 12 volts . I would only need air for an hour or so each day . Nothing else on batteries except normal pumps and lites .


As someone said 13.5k A/C draws around 13 amps of 120 vac. That is around 130 amps of 12 vdc. Don’t know what starting amps is but a soft start would help. Strangly a 15K AC.. about the same amount (I was surprised when I upgraded my Carrier (That's what I had 13.5K and that's what it drew 13.5 amps) to a 15K (Carrier is out of the business so it was a different brand) it also drew 13.5 Running bit more on the start)

4 GC-2s is about 440 Amp hours at the 20 hour rate about 200 usable by the inverter (I suspect it has a cut off).. One hour would be about 135 amp-hours But wait there another factor Peukert's law Basically it says "The faster you draw down a rechargable battery.. The Faster still it runs down"

That is at that discharge rate you wont get anywhere near the full capacity of the battery. And no.. I do not know how bad it will be.


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theoldwizard1

SE MI

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Posted: 07/20/22 06:10pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:


3000w inverter should have no issues.

Better get a Micro-Air EasyStart !

2oldman

NM

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Posted: 07/20/22 06:40pm Link  |  Quote  |  Print  |  Notify Moderator

theoldwizard1 wrote:

Better get a Micro-Air EasyStart !
Don't think you need one with an inverter.
wanderingbob wrote:

Assuming that I have the battery power would a 3,000 watt inverter run a rooftop 13,500 air for an hour or so

An hour?.. that may be pushing it a bit. LA batteries, especially just 4, will likely lose too much voltage over that amount of time and shut down the inverter. Plus, wires and connectors - and even the batteries - are going to get hot if not sized exactly and clean and fresh. Plus you need them to be at nearly 100% charge. I used a lot of high-wattage appliances with 4 batteries, but I found 6 to work much better. It's just a whole lotta weight.

I think an hour may be just too much.. but hey, prove me wrong!

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