I want more than I can afford.

[666JTK666]

been looking at lifepo 4 batterys, spcificly 1000ah batt's.
dream setup would be 28v so that's 9 cells at 3.2v each.
each battery cost's around 850$$ each.
I could maby buy one of thoes every 2 months.
life sux.. lol
I want enough power for my ac unit to run for at least 8 hours while I sleep.
my ac unit say's on the back that it's a 1000 watts I am assumeing that is with the compressor and fan on high. I really need to get a kill a watt meter and find out for sure what the true power draw is.

 

[DannyB1954]

1000 watts divided by 28 volts is 35.71 amps times 8 hours is 285 amp hours.
1000 watts divided by 12 volts is 83.3 amps times 8 hours is 666. 6 amp hours.
When the compressor first starts it will dray more amps, and when it cycles off it will draw less, so I will call it a draw.
To me it looks like using 1000 amp hour batteries, you could get by with a 12 volt system, or 4 batteries.

 

[666JTK666]

been looking at lifepo 4 batterys, spcificly 1000ah batt's.
dream setup would be 24v so that's 9 cells at 3.2v each.
each battery cost's around 850$$ each.
I could maby buy one of thoes every 2 months.
life sux.. lol
I want enough power for my ac unit to run for at least 8 hours while I sleep.
my ac unit say's on the back that it's a 1000 watts I am assumeing that is with the compressor and fan on high. I really need to get a kill a watt meter and find out for sure what the true power draw is.

Edited the voltage, 24v not 28v my bad.

 

[666JTK666]

1000 watts divided by 28 volts is 35.71 amps times 8 hours is  285 amp hours.
1000 watts divided by 12 volts is 83.3 amps times 8 hours is 666. 6 amp hours.
When the compressor first starts it will dray more amps, and when it cycles off it will draw less, so I will call it a draw.
To me it looks like using 1000 amp hour batteries, you could get by with a 12 volt system, or 4 batteries.

hi sorry I gave the wrong voltage and that changes things.
I believe that lifepo4 batterys are 3.2v so for a 24v setup I would need only 8 cells =25.6 volts
useing your calculation's I would need 334ah(rounded up) for 24v.

believe me I am looking at my options like 6v trojan agm's and anything else I can think of.

 

[Trebor English]

See the thread "Promising initial Off-grid AC test" by BradKW. It isn't about lithium but it is about battery powered air conditioning.

 

[John61CT]

Running A/C for extended periods off a battery bank is a rich man's game no matter what.

 

[BradKW]

Running A/C for extended periods off a battery bank is a rich man's game no matter what.

Depends I guess...I certainly am not rich  

Basics: 1kw solar @ $0.60/watts = $600 in panels, + (4) Trojan L16 batteries for around $1300 + inverter... so buy in is around $2500 - $3000 for something that could be reasonably be expected to power AC for 5-8 hours continuous run.

Of course, cycling off extends duration and insulation will likely play a big role here. And downsizing to a smaller AC unit would make a big difference. Zoning interior sleeping area could make a big impact as well.

Initial Off Grid AC test

 

[John61CT]

There will be many unanticipated expenses to get everything running right.

Over in the YACHTING forums, people with small boats, only 40-50', that cost ONLY $200-300,000, usually conclude not worth trying

Domain of the mega yachts, gennies / engines would usually be running 24x7 anyway, but some owners want it more quiet at night, so just an extra drop in the bucket for them, NP.

 

[jonsun]

Here's what you do


build a box with 3/4" plywood. drill vent holes on 2 sides and screw a radiator to inside of box. Drill a 1" hole in the bottom corner. Now drop in a $300 generator with an electric starter and tack weld, fasten, rig a pipe on the muffler that will run out of your bottom hole. Wire fan to 12v output on the generator.

Now put that on a simple hitch tray.


if you want to get super fancy build an upper compartment to hold an extended run gas can that connects right to fuel tank.

Now you can both find some shade and keep cool all you want.

 

[DannyB1954]

hi sorry I gave the wrong voltage and that changes things.
I believe that lifepo4 batterys are 3.2v so for a 24v setup I would need only 8 cells =25.6 volts
useing your calculation's I would need 334ah(rounded up) for 24v.

believe me I am looking at my options like 6v trojan agm's and anything else I can think of.

Lifepo4 batteries can be drained to a greater degree than other batteries. If you used 500 amp hour batteries, that should do it. 

Like others have stated, your challenge would be recharging that amount of energy. If you plan on solar panels, You will need probably in excess of 1,200 watts of panels, ( they rarely output their rated maximum). Do you have room for them? If you recharge with a generator, you will be running it for probably 4 hours every day. 

An option that I am exploring is to run an A/C unit from an inverter and having a small quiet generator charge the battery while the A/C is running. This should allow a smaller generator to be used. I think a 1,000 watt unit should do it. When the A/C compressor first starts it will probably draw 1,400 watts. This is more than the output of the generator. The unfunded energy will come out of the battery banks. When the compressor shuts down, the generator / battery charger will put the energy back into the batteries. A small generator will run 8 hours on a gallon of gas.

 

[jimindenver]

Lots of things I wish I could afford and I can run my A/C all night if needed. It took finding the most efficient A/C, Buying used but unused batteries and some fairly expensive solar gear to recharge them the day. Then again if it is that hot at night, it must really suck all day which means even more solar.

You can't afford a lot more than batteries.

 

[jimindenver]

Danny
I have done what you are describing with my converter plugged into my 800w inverter generator and my 450w/5000 BTU A/C plugged into my inverter. The generator can not start the A/C on its own but it can power it once the batteries have taken the surge.

 

[amwbox]

Running A/C for extended periods off a battery bank is a rich man's game no matter what.

The conventional wisdom changes. Panels are getting more efficient, and far cheaper. AC is getting more efficient as well. Batteries are one of the most heavily researched techs going. Its only a matter of time.

For a modest investment, people are already running AC off grid.

But yes...its certainly cheaper to sit there and be hot.

 

[amwbox]

There will be many unanticipated expenses to get everything running right.

Over in the YACHTING forums, people with small boats, only 40-50', that cost ONLY $200-300,000, usually conclude not worth trying

Domain of the mega yachts, gennies / engines would usually be running 24x7 anyway, but some owners want it more quiet at night, so just an extra drop in the bucket for them, NP.

A 40 or 50 foot boat is NOT small. Much bigger than that and your getting into the realm of the mega yachts. 
A guy in my marina sailed around the world on a 24 footer. 

In any case, solar on a boat is MUCH harder to do, as solar panels don't much like the constant motion, the windage, the shadowing from overhead masts and rigging (almost impossible to avoid), and corrosive salty environment. Lots of boats with solar, but its relatively minor in terms of actual output. Vans and RV's have the capability to do a LOT more solar, and a lot more efficiently. Boats usually charge off of alternators, and carry healthy battery banks. BIG boats, like the 50 footers you describe, are where you start seeing generators. But those are much less common. Hell, even the world cruising blue water sailing set only average around 40 feet. The vast bulk of boats are probably mid 20's.

 

[jonsun]

aft cabin ski boats are usually like 30ft

 

[Every Road Leads Home]

When you're in the middle of the ocean 50' feels REALLY small, i've always envied the guys (and girls too) that sail around the boat in the 20-30' range. Balls of brass.

Agreed, solar on a sail boat is an entirely different beast. The best systems on sail boats seem to be when they build a rack that hangs them off the stern.


Is a generator out of the question for you? Sounds like a mix of solar and genny will yield the best results for AC use. And if you hit a stretch of cloudy days you can still recharge everything.

 

[jonsun]

forget generators and propane. just build a 10kw array with a 4k amp bank that way you can run your space heater for 10hrs in the winter too.

 

[amwbox]

When you're in the middle of the ocean 50' feels REALLY small,  i've always envied the guys (and girls too) that sail around the boat in the 20-30' range.  Balls of brass.  

Really depends on the boat. There are quite a few heavily built smaller cruisers that were specifically designed and built for crossing oceans. I'd take one of these over a boat twice the size that wasn't built to same standards. Been sailing on the N Pacific since I was a kid. I'd not hesitate to go in something like this:

^But again...she was built for it. Sorry to wander off topic. Love me some boats...and they are kinda like RV living...if not particularly cheap...

 

[akrvbob]

Let's stay on topic. Boats are NOT the topic of this thread.

 

[amwbox]

...

As I said. Sorry to wander off topic.