Portable A/C unit

[philo111]

have a Camper Box Truck with a 14' box. I also have a 10,000 BTU portable A/C that uses 1200 watts / 10.8 amps).
I would like to run the A/C for several hours without a Honda type gas generator.

I was thinking:
I could upgrade the Truck Alternator to one that produces
100 amps at idle.

Get a good quality Deep Cell Battery that holds 200 amps.

Get a 3000 watt inverter.

Plug in the Portable A/C.

Start the Truck and just let it idle for hours when the A/C is
on (the engine does not over-heat).

Would this work?

Thank you for your thoughts!

[96Bounder30E]

This duplicate post is closed

[westend]

I'm just curious of what alternator the OP has?

[okhmbldr]

Yes, it will work.
I did the same thing four years ago with a 12,000 btu portable and a deep cycle battery.
My application was a little different. I used the a/c at night in a 28' Rinker cabin cruiser on a trip down the Arkansas River to the Mississippi.
I did a test before the actual cruise. I took a fully charged battery, hooked up the inverter and let it run in the garage. I lasted four hours before the inverter shut off because of lack of power in the battery. Since I was using it at night, the four hours was enough for me.
I recharged the battery each day as I continued on my trip down the river.
Just do a few tests and see what happens.
You may need two batteries, depending on how long you want to run your a/c.
Let us know how your test works out.

[theoldwizard1]

Are there any web sites that list energy consumption for household appliances like A/C and refrigerators ?

[theoldwizard1]

MrWizard wrote:
... you may find the project costs more in time and money than you think

Yep ! A MagnaSine MS2812 2800W inverter and a battery will be over $2000 ! :E

[Allworth]

Emissions are NEVER a non-issue!

[MrWizard]

BTU "British thermal units"

when comparing with electric heat 5000BTU, that is approx 1500w

BUT when comparing with cooling, it is not a linear transfer
its all about compressor efficiency, condenser and evap coil sizes etc..

10000 btu cooling does not need 3000 watts power
the 10.8 amps sounds correct, and runs on a normal 15a 120v home circuit

still the LRA of the compressor comes into play, and the ability of the inverter to supply this FOR the "Seconds" needed to start the compressor

the surge rating of many inverters is listed in Micro-Seconds or Milli-Seconds, not real Seconds of time

not enough time to start the compressor on most A/C units

you can hear a compressor start up on a strong enough generator or shore power, thats because it takes time to spin up against coolant pressure, its not blip like flipping a light switch

an inverter that has a surge time that is a mere BLIP won't start the a/c compressor

yes there are inverters that can power your a/c,

you may find the project costs more in time and money than you think

[theoldwizard1]

philo111 wrote:

The alternator is rated at 100 amps at idle and 200 amps at 1200 RPM.

WOW ! Those are some specs !!

Lock Rotor Amperage is pretty much the maximum an air conditioning compressor will draw under "worst case" conditions.

Like I said earlier, newer window shakers draw less current.

[azrving]

Locked rotor amps. Could you use a 5000 btu? I used one in an insulated one car garage. Isn't that 10,000 btu supposed to be on a 20 amp circuit also?

[philo111]

rjxj wrote:
What are the lra on that ac unit?

I'm sorry, I don't know what Ira is?

[azrving]

What are the lra on that ac unit?

[philo111]

donn0128 wrote:
1, truck motor at idle will burn lots of fuel and lots of polution
2, 100 A alternator is rated amps at XXX RPM, not at idle
3, a single battery can only supply about 50% of its rate before it is considered dead.
4, 10.8A at 120VAC means the inverter will draw approx 110Amps at 12VDC to run the load.
Any more questions?

Thanks for the reply.

The alternator is rated at 100 amps at idle and 200 amps at 1200 RPM.
The truck idles at .2 gal. per hr.
The emissions are non issue.

Still not positive why this won't work?

[theoldwizard1]

Hmm ... I wonder why those guys were so quick with one word answers !

I will say "Maybe !"

2 problems against you.

1. Truck charging system. If you really want to try this, you really need to bypass the trucks battery and hook up the alternator directly to your deep cycle battery. That, and you will likely have to come up with a way to run the engine at "high idle".
   
2. A/C starting surge current is a big problem. Newer portable A/Cs draw less.

If you are going to try this, make sure you have a GOOD pure sine wave inverter and you are going to need something like a Trojan J185H-AC battery ($300) or LARGER !

Also, when you are done running the A/C, you need a good 3 stage battery charger. Hook the track battery back up, hook the inverter to it and then re-charge your other battery. This might take a couple of hours !

[spoon059]

Carbon monoxide poisoning sounds like one major reason why its a bad idea.

It sounds like the ideal solution is a smaller inverter style generator, which you have already ruled out. To me, the better question is "why" or "how come" you won't use a proven tool to do the job you want done?