Battery Power Advice Needed

[leesurevan]

Hello everyone,

I'm new to the van game and I'm beginning to convert my 1997 E350 Cutaway Shuttle Van into an RV. I've got all the blueprints of the architechtural design finished, next is the planning phase for what my source of energy will be, this is the area I'm only familiar with from what I've read online.

My goal is to have 1 or 2 solar panels on top of the van that are constantly charging 2-4? deep cycle batteries, however, this will not be my only source of electricity. The deep cycle batteries will only function to power small floor standing portable ac/heat unit if needed, possibly TV as well, but mainly just for lights and charging an occasional laptop or something but only while we are off grid. We also plan to have a small generator to crank if needed.

Basically, I'm wondering if anyone out there knows exactly how many deep cycle batteries I will need to run the simple function of a small ac/heat unit for multiple hours. I know it all depends on size of the AC unit etc. but I'm curious to know if anyone has had experience with running one in conjuction with deep cycle batteries. ANY info is greatly appreciated.

-JL


1997 Ford E350 Cutaway Shuttle Van 
7.3L Powerstroke Turbo Diesel W/ 149,xxx miles

 

[bcbullet]

AC? Ouch...
As has been said many times before, It is far easier to adjust your "needs" to suit the installation than to adjust your installation for your "needs".

 

[ccbreder]

AC or Heat? not with the number of batteries that will fit in a van.

 

[leesurevan]

The unit I was looking at is 8,000 btu ac and heater.

OK so i'm assuming its going to take much more power than the means of 4-6 batteries will supply to power the ac unit?

so i'm guessing if I were to start with 3-4 deep cycle batteries, would that be sufficient means to power about 6 lights and maybe charge some phones or computer, possibly a tv for 1-2 hours tops?

 

[jonsun]

That would be incredibly silly. You have a generator, run the AC off that. For lights, occasional tv, etc one battery and one panel will be just fine. Plus....You have a generator.


Edit: you are talking group 29 batteries, right? You might need 3_4 for lights if you're using motorcycle batteries lol

 

[ArtW]

Yeah, a Genny is gonna make a lot more sense for the AC / heater

 

[tbair]

The unit I was looking at is 8,000 btu ac and heater.

OK so i'm assuming its going to take much more power than the means of 4-6 batteries will supply to power the ac unit?

so i'm guessing if I were to start with 3-4 deep cycle batteries, would that be sufficient means to power about 6 lights and maybe charge some phones or computer, possibly a tv for 1-2 hours tops?

Just to give you an idea of the calculations you want to do:

A deep cycle battery (group 31 a common deep cycle size) is usually about 120 amp hours X 12 volts = 1440 watts. Usually if you want to keep your batteries around for a while you only will use half the capacity  = 720 watts is what you have in the tank (at best)

A 8,000 btu ac, even energy star will use 500-700 watts per hour. So rough guess you will need 8-10 batteries to run your AC for 8 hours. 

This neglects a whole bunch of losses that may be present due to wire size and high amp draw and inverter inefficiencies but you sort of get the idea. 

Basically, add up how many watts you will use, multiply it by the hours you use it, get a total and divide by you battery capacities. No one can say what you need because we don't know the wattage of your lights or how long you want to use them etc.

Hope that helps a little, and that I did not screw up any math in my head

 

[DannyB1954]

A/C units take a lot more energy when first starting. So if the tag says it runs at 10 amps, that is probably 15 to 20 amps whenever the compressor first starts up. Watts is the result of multiplying the amps times the volts. So 10 amps at 120 volts would be 1,200 watts. To find how many amps that would be at 12 volts it is 1,200 / 12 or 100 amps. A few batteries tied together will not put out that kind of amperage for more than several minutes. If your roof was large enough you could put in 2,000 watts of solar panels, but the cost would be great for that type of system.

If you need A/C, you will need a generator. When shopping look at the ratings for continuous output, not peak. My best guess is you will need a 1,800 watt continuous generator. Then if a household plug would run it, the generator probably will as well. 1,800 watts divided by 120 volts is 15 amps.

Most electric heaters are 1,500 Watts, 1,500 / 12 is 125 amps. Propane is probably the way to go for heat.

 

[jonsun]

Even running a 2000w generator its going to use $10 A DAY in fuel. They go about 6.5hrs per gal @ 50℅ load. That's $300 a month.

Might as well just look at campgrounds and forget the batteries and solar for that much $

 

[jonsun]

Here's the real answer for what to do.

Cant use compressor AC's and you cant use electric heat. We just showed you why. just forget it now.

you can use propane heat and an evaporative AC. This allows for nearly all solar production...but you still dont want to do that. Its too expensive.

so you build a 2-3 battery bank with 250w of solar or somewhere like that. then you get an RV 3 phase charger that can put out a bulk charge of 40-50A and run the generator an hour or two to get the batteries up to 80%. Then the panels will charge the rest. at peak sun with 3 batteries and 250w of solar the load should be around 5-7 amps and you will have about 17A coming off the panels so you'll have just enough to run the system and top off the batteries.

with a small genset it will cost about $.75-1 a day in fuel

 

[leesurevan]

Awesome, that tells me exactly what I need to know. I really appreciate all the feedback. Definitely gonna go the generator route, but do plan to use RV sites as well, as for lights and small electronics, I may consider a small solar panel and a couple deep cycle batteries.


Thanks again for the knowledge.
-JL

 

[Optimistic Paranoid]

I may consider a small solar panel and a couple deep cycle batteries.

The rule of thumb is that you need one watt of solar panel for each amp hour of battery capacity.  Two golf cart batteries should be around 200 ~ 220 amp hours, so you would want a 200 watt panel to take care of them. 

If you spend most of your time in the Desert Southwest, you might get by with a little less watts.  In the rainy Pacific Northwest, you will probably need more watts.

 

[blars]

Technomadia can run their air conditioner for a few hours with 500Ah of LiFePO4 batteries. You might be able to do it with 2000Ah of lead-acid, or about 18 golf cart batteries. (at 60 pounds each) They now have 800 watts of solar, with an additional 800 watts portable to put out as needed, and are planning to go to 1000Ah of LiFePO4.

 

[jonsun]

damn, what's that about $10k in batteries? Or, who's making lithium deep cycles?

 

[jimindenver]

JL

I run a small 5000 BTU window A/C off of my 750w of solar and 675 Ah of battery (471 pounds) or roughly the equivalent of six 6v batteries. I saw a van at he RTR with four 250w panels on a rack that could do the same.

The 5000 BTU A/C is the lowest watt usage i could find at the time rated at 450w, now there is one that uses 410w. were I to buy now it would be a variable speed 12000 BTU portable that starts at 1100w then drops and holds at 300w. I am adding a 435w tilting panel to the trucks roof but am maxed out on battery space.

So it is feasible, it just depends on how bad you want it.

 

[ccbreder]

Get two GC2 batteries. Connect in series for 12 volts. These are true deep cycle, not just a label calling them deep cycle.