Want to Build an Off-Grid Battery Pack to Power an Air Conditioner ... Possible?

[tmoney]

Hi everyone.

first of all I'm a newbie to all this solar stuff. I've been reading a lot of threads and wanted to build a battery pack setup strong enough to power my portable air conditioner in the summer time.

I guess my questions is, what will I need to make this happen in terms of panels, batteries etc.

Specs:
10,000 BTU
8.5 amps
115 volts
977.5 wH

I only would need to use use the air conditioner for about 3-4 hrs a day. Is this possible?

Thanks in advance.

[Mike90250]

Specs:
10,000 BTU
8.5 amps
115 volts
977.5 wH

I only would need to use use the air conditioner for about 3-4 hrs a day.
Is this possible?

Nearly anything is possible, except going to the moon.

977.5W x 4 hours = 3910WH
to allow discharge only down to 50%, to give you reasonable battery lifetimes, you need to store twice that amount = 7820Wh round up to 8,00WH for easier math.
At 48V, that's a battery with at least 167 AH capacity. So you would need 4 each, 12V batteries of at least 167AH capacity.

And a Sine wave inverter, 'cause your air conditioner has at least 2 motors in it, that will be much happier on sine wave. About a 2,500W inverter should work, if it has a surge capacity that can start the compressor motor.

If you have any money left over now, you could buy a battery charger, to recharge this with. a 48V charger at 20A would do the job, overnight, Solar, you would need about 40A to recharge in the few hours of sun you have.

Alternatives:
price out that 300' extension cord again.
Look into a honda EU2000 generator and a gas can, seriously.

I've not even gotten into cables, fuses and all that stuff.

[tmoney]

Thanks for the reply!

From what you've said, it doesn't seem to make sense (financially) to buy all that equipment when I can just run the unit from the grid for under $1/day.

Maybe I'll look at a smaller setup to run a few small things instead.

One other quick question.... with a battery setup that is recharged by solar, you mentioned that you should try and keep the charge at at least 50% to maintain a longer life? How long do you think a battery would last if I just drained them every time every time I used them?

[Mike90250]

This site has a chart about the Cycles vs Depth of discharge



http://www.mpoweruk.com/life.htm Traction Battery (Forklift) life chart

[kilam57]

Back-up Batteries

Make sure you use sealed batteries for your emergency back-up battery banks. Wet cell batteries need watering every 3-4 month. If they aren't they will become stiff and chemically resistant. Therefore, they won't be able to deliver the power when needed. Solar power generators are the way to go.


[ Clickable link to site broken by moderator & comment does not follow thread ]

//how-to-build-your-own-solar-panels.com/all-about-solar-power/solar-power-generators-can-save-you-up-to-17-on-your-utility-bill/

[Sunking]

I only would need to use use the air conditioner for about 3-4 hrs a day. Is this possible?

Well it is possible, but the question is why on earth would you want to pay 10 to 30 times more than you would pay the electric company?

[Sunking]

Mike I think the graph is greatly exaggerated. I do not know of any FLA battery on the market that would provide 500 cycles at 100% DOD. More like 30 to 50 cycles.

[Mike90250]

The source page lists forklift batteries (traction) as able to take that abuse.

http://www.mpoweruk.com/life.htm

but the chart gets the idea across, the deeper the cycles, the fewer. An automotive starter battery could take maybe 3 or 4 100% discharges when it dies. RE batteries might take as many as 50 as you so eloquently stated.

I didn't make the chart - just posted it.

[Sunking]

I didn't make the chart - just posted it.

I know Mike, sorry if I offended you, that was not my intent.