Running AC off Batteries?

[wakerider09]

Is it possible to run an AC unit of batteries, a small 5000 BTU unit? Obviously the deal practice is shore power or with a generator, but could you designate a separate battery bank to run AC for isolated periods just to get the humidity out of the cabin?

 

[theoldwizard1]

Re: Running AC off Batteries?

Almost anything is possible given enough time and money. On a boat the third limitation is space. You might have the time, but probably don't have the money or the space. You would probably need 3-8 of the biggest marine batteries you can find and even then you'll only get a few hours of run time.

 

[H20Rat]

Re: Running AC off Batteries?

Is it possible? Yes... For how long is the question... A 5000 AC will draw around 650 watts, so 54 amps at 12v. Add 20% for inverter loss, so 65 amps. Group 29 deep cycles are usually around 100 amp hours, BUT... that is for a low amp load, 1 amp per hour. Drawing 65 amps constant will give you well under an hour runtime, I'd say more like 30 minutes MAX unless you want to seriously shorten the life of the battery.

On the other hand, if you are wiling to take the hit in weight and set up a proper battery bank, it can be done. 4 or 6 6v-trojan batteries would give you a decent amount of runtime.

(Disclaimer, you need a VERY healthy inverter to start up an AC unit, minimum of 2000 watts if not larger.)

A small 2000+ watt suitcase generator would be a much better choice for intermittent use like this.

 

[UncleWillie]

Re: Running AC off Batteries?

...A small 2000+ watt suitcase generator would be a much better choice for intermittent use like this.

+1
And much lighter too!
A 100AH (1200wH) Battery is equivalent to ~1 Pint of Gasoline. (~10 oz weight)

 

[bruceb58]

Re: Running AC off Batteries?

Running an AC off batteries is a losing proposition. You might get 20-30 minutes out of a battery before its time to recharge. Generator is the only way to go.

 

[MH Hawker]

Re: Running AC off Batteries?

A good fan will keep it nice for the most part.

 

[Scott Danforth]

Re: Running AC off Batteries?

a $6 12 volt fan and 2 containers of rid damp for $6 and it will take the humidity out

 

[Slip Away]

Re: Running AC off Batteries?

Running an AC off batteries is a losing proposition. You might get 20-30 minutes out of a battery before its time to recharge. Generator is the only way to go.

This. Can the AC on battery or invertor idea.

 

[Fireman431]

Re: Running AC off Batteries?

Dehumidifier??

 

[H20Rat]

Re: Running AC off Batteries?

Dehumidifier??

Dehumidifiers aren't any better, they are just A/C units that don't vent to the outside. They still have a big motor spinning a compressor, and draw a ton of power.

 

[theoldwizard1]

Re: Running AC off Batteries?

A small 2000+ watt suitcase generator would be a much better choice for intermittent use like this.

If you shop carefully, and find a small, efficient A/C unit, (3,000 BTU ?) you ca actually run them off of a Harbor Freight 800 watt generator.

 

[H20Rat]

Re: Running AC off Batteries?

If you shop carefully, and find a small, efficient A/C unit, (3,000 BTU ?) you ca actually run them off of a Harbor Freight 800 watt generator.

Have you actually tried that? Startup current for an AC is 3x or more, so I would have my doubts about it actually starting the load. Even a drill would pop the breaker on mine if I hit the trigger too fast, and an unloaded drill is certainly a lot less load than an AC compressor!

Personally, I owned one of those HF 2 stroke generators, biggest piece of steaming #@#% ever. First problem was that it was extremely picky, and only ran when it felt like it. Next, assuming you actually get it started, it is LOUD. Think chainsaw running full bore loud. Lastly, the voltage it puts out barely qualifies as usable. It swings from 80v to 190 volts. The waveform looks like a picture of the side profile of the great pyramids. After seeing the voltage and scope output, I would never connect anything other than worklights to those generators, ever!

 

[theoldwizard1]

Re: Running AC off Batteries?

Have you actually tried that?

I have not, but there are videos on YouTube showing it does work on an 3,500 BTU window A/C.

Personally, I owned one of those HF 2 stroke generators, biggest piece of steaming #@#% ever. First problem was that it was extremely picky, and only ran when it felt like it.

First, I hope no one takes my comments as any kind of endorsement for that product, especially since I DO NOT OWN ONE !

Reading stories on the Internet, it is clear that the "things gone wrong" rate on this generator runs about 4 to 5 time the rate of positive experiences.

If someone does want to take a chance on one of the generators, here is a couple of tips I picked up in my readings !

• Pay the extra for the extended warranty. The chances are your will use it !
• Replace the stock spark plug with a name brand (NGK/Champion) and have always have a spare.
• Get familiar disassemble and reassemble the exterior sheet metal. Your will be doing it often.
• I would probably replace all of the fuel lines with Tygon and use good clamps.
• I would also probably use full synthetic 2 stroke oil. Expensive, but it will help prevent crabon build, a common problem in 2 stroke engine.
• Every time you refuel, you should do an inspection for loose fasteners and connectors.
• Most of the fasteners should probably have a drop of Locktite.

Not much you can do about the noise and they are loud.

The bad thing is, when you need a generator it is probably because some main system has failed. Nothing worse than having the back up fail,

Video (not mine) on Improving HF 800 watt generator reliability

 

[Watermann]

Re: Running AC off Batteries?

If your really serious about your boating, cabin sleeping and stingy with your money then look around for a donor camper that may be damaged and selling on the cheap. Strip the AC unit off the top and it's generator. They are a match and WILL work together.

 

[Mason78]

Re: Running AC off Batteries?

How big is the cabin and how long do you want to run the AC?

I made a homemade AC unit using a 12 volt fan, igloo cooler and PVC pipe that works great for a few hours but it only cools my tent!!:happy: