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Discussion Starter #1
Hey guys, so I’ve asked in another van forum and was told it is basically impossible to run a/c off batteries. I’m looking for second opinions. What kind of setup would I need to run some a/c without a generator/shore power.
I’m in Texas and building a motocross camper van. Will probably stay in cities a bit on weekends and don’t want people knowing I’m camping. Or on just trips in general.
Would a lithium setup work to run it for idk 5-6 hours on a super low setting? Are there low wattage van specific a/c units? Doesn’t have to be ice cold, just enough to make it more comfortable than fans alone. Any suggestions?
 

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There are some remote condenser units that are from marine applications and are a bit lower power, but I'm fairly certain the wall you're butting up against is energy capacity of reasonable 12v banks. It takes a lot of energy to cool something down and that is best drawn from liquid fuels than electric banks.

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I've got 600aH Lithium and I have easily run my rooftop A/C (thermostat set at 77) for seven plus hours on a Florida summer night - with more than 30% battery remaining come morning. It'll run non-stop during the day for maybe three plus hours, fighting the hot sun. But, wife turns on a hair straightener in the morning and that 30 plus percent drops in a HURRY.
 

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I've got 600aH Lithium and I have easily run my rooftop A/C (thermostat set at 77) for seven plus hours on a Florida summer night - with more than 30% battery remaining come morning. It'll run non-stop during the day for maybe three plus hours, fighting the hot sun. But, wife turns on a hair straightener in the morning and that 30 plus percent drops in a HURRY.
So now even if your wife doesn't turn on the hair straightner how are you going to get that massive battery bank charged back up ??
$6000 worth of batteries to run a air conditioner?
 

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Second underhood alternator. It's a Coachmen, with the Li3 battery package. Hit the road, or idle it, and the battery will charge. You wouldn't want to spend multiple days, not moving, trying to keep the van cool. I'd call it more of a 'capability', not a normal day to day expectation.
 

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Second underhood alternator. It's a Coachmen, with the Li3 battery package. Hit the road, or idle it, and the battery will charge. You wouldn't want to spend multiple days, not moving, trying to keep the van cool. I'd call it more of a 'capability', not a normal day to day expectation.

Do you also have the high efficiency 12 VDC air conditioner, or is yours the standard rooftop type powered by an inverter?
 

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Second underhood alternator. It's a Coachmen, with the Li3 battery package. Hit the road, or idle it, and the battery will charge. You wouldn't want to spend multiple days, not moving, trying to keep the van cool. I'd call it more of a 'capability', not a normal day to day expectation.
Sounds like a good system for somebody that travels alot.
Coachmen Ftw
 

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Discussion Starter #8
So sounds like it is only possible if I spend a serious ton of money? 600ah of lithium batteries is what close to $6k? I think the battle borns are $900 per 100ah.

Man I really was hoping for a better option. It seems like there should be a low wattage a/c just to make it a tad cooler for vans.
 

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Over the road truckers have been doing it for the last 4 years with 800 Ah of Agm batteries. These are packaged systems often called Truck APUs. Carrier and Thermo-king are the best known makers of these systems but there are others.
 

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Rooftop ac? Either a large battery bank (and large charger), or idle engine and wire a 2000 watt pure sine inverter to power AC off vehicle alternator (requires HD alt). I choose idle engine for the times I want rear AC. I don't live in my van so it's a practicable solution.
 

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Not the 12v a/c. 110v.
Thanks.

I thought maybe you had the optional 20,000 BTU/hr 12 VDC rooftop unit. It pulls 96 Amps (95F) at 12 V for about 1,150 Watts, which is an EER of about 17. That’s really good compared to standard RV rooftop A/Cs, particularly after inverter efficiency is taken into account. Too bad it’s so large — few need 20,000 BTU/hr to sleep in a van.
 

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For nighttime use only, I’d love to try one of these smaller (lower capacity) A/C units out, but expect the initial cost is very high. Although not as efficient, power demand of as little as 15 Amps at 12 Volts (180 Watts) is appealing. A couple of large AGM batteries may cool a small area all night.
 

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FWIW, I have the HD alt, implemented the SEIC function to idle at 1500rpm, a magnum 2800w inverter, and coleman mach 8 pup rooftop AC. I can idle and run the AC no problem without drawing anything from the house bank. I can also run the AC from the house bank, but with only 300H of AGM, that wld not last long, perhaps 45 min w/ full charge. But dont need the house bank for AC due to the HD alt, SEIC, etc.
 

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I just watch a video by Jarrod Tocci yesterday and the van (very nicely done van) had 12V AC. They mentioned it quickly so you would have to listen to the video and try to catch the name. Since I just joined, the forum does not let me post a link but here's the name of the video "VanLife Tour: A/C, Heated Floors, Huge Power System, Back Seating...What else could you need?!" you can just search for it.
 

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"I just watch a video by Jarrod Tocci yesterday"


In yesterday's live stream, Jarrod mentioned he has provisioned for a DC A.C. unit (the mini-split type for marine use) and will install it next summer. He has enough battery capacity and charging capacity to do this.
 

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We build aux electrical systems for battery powered air conditioning systems for customers. I built one for myself a few years ago (as the proto).

It isn't so much a technical question anymore, really just a financial one.

In approximate terms, it takes about 1 kW-hr of usable battery capacity for each hour of air conditioning run time, so ~ a battle born battery per hour.

The two most common strategies are:
- 4 batteries ~ 3-4 hrs of run time, then auto start either the engine to re-charge some, or a generator
- Essentially 2x this capacity, so that you can make it all night

Budget wise, the smaller (electrical) systems are going to cost ~ $12 K to implement, regardless of if you DIY or hire someone.

A dual alternator transit (or even a promaster) is a good starting point for systems like this.

A cheaper alternative is to buy a honda or yamaha 3000 size generator, locate it inside of an muffled box off the back door and run it off of that. The 3000 size generators have a large enough fuel tank to run all night, while the smaller ones do not.
 

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I am interested in this as well. I am trying to learn what I can about mini splits and the possibility of running one of these in my van. I like the efficiency, low startup, and the heat pump. The issues I see are around mounting and space needs as well as them not being engineered to bounce down the road. There seems to clearly be a need for a RV/van specific mini-split product. Apparently, these can run off of a 1000W inverter pretty well.

This one seems to be the closest fit I have seen - https://www.amazon.com/dp/B00UV3LGPY.

One of the reviews has a photo of one mounted on the rear of their van. That doesn't seem to be the most elegant of mounting positions, though.
 

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Such a good post. Thanks OP and all those who commented.

I've been working on this same problem and had come to the conclusion that a second alternator, plus a large (600-800 AH) lithium battery bank was the answer.

Solar could also be included (at more cost) to charge the banks whenever possible, with idling the van as the backup. But cost kept me on the first option and not adding solar.

But for the rooftop model itself, I have heard that 12v systems are the most efficient because they don't require power to be routed through the inverter. That also means no noisy inverter fans running at night and no inversion loss/heat generation.

What I can't determine is the best 12v model for a high roof Transit. These options posted above are very useful, but it's hard to find clear information about this.

Harryn's post was very intersting: "A cheaper alternative is to buy a honda or yamaha 3000 size generator, locate it inside of an muffled box off the back door and run it off of that. The 3000 size generators have a large enough fuel tank to run all night, while the smaller ones do not."

But that means refueling the generator every morning (ugh), or tapping into the fuel tank of the van, which means more frequent trips to the station (not good for off grid), and issues with the fuel gauge accuracy.

Bmzero's mini-split looks interesting, but that external fan is enormous and looks unwieldy no matter where you install it.

I'm still researching this, but I've heard that ProAir specializes in these types of solutions (probably expensive though). For instance, all kinds of condensers that are much smaller and roof or under-carriage mountable here: https://proairllc.com/system/condensers/

They also sell repurposed 12v prius compressors and various other heating/cooling custom solutions. I heard about them from the guy who sold these vanlifers their electrical components. He said they hvae a very efficient and really well-designed system. Here is a video they did (12:15 is where it gets into the system itself):

Does anyone actually have a 12v system running, or have a clear idea of the pros and cons of 12v system versus standard 120v + inverter?

Thanks!

Mark
 
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