Keeping a roof ac going without using the generator or shore power

[jan50]

I've heard about the etrek from Mike Wendland. He is kind of like an unofficial spokesperson for Roadtrek. He and his wife live in their Roadtrek and he writes about it and has a web site dedicated to it. I read on his web site that he traded in his etrek for another Roadtrek because he had a lot of difficulty keeping the batteries charged. Roadtrek has since come out with something new that takes care of this problem - something new with lithium batteries.

[sandsys]

A generator needs regular exercise under load. We used to run ours while driving to power the house A/C so we wouldn't bother neighbors with generator noise while parked.

 

Linda Sand

[Jfet]

The simple answer is that it can only be operated from shore power or an on-board generator. Even if you had an inverter that was large enough to supply it power, which I've never seen in an RV, you would need a far bigger alternator added to the main engine to supply it the needed power. While it is actually possible to make that work, it is completely impractical.

 

Eh, we have a 4kW Magnum inverter running on a 24V system in our RV which is plenty large enough to power a A/C. The limit is battery bank and solar.

[Kirk W]

 

Eh, we have a 4kW Magnum inverter running on a 24V system in our RV which is plenty large enough to power a A/C. The limit is battery bank and solar.

Based upon your profile, you also have a custom built RV.

[Jack Mayer]

Based upon your profile, you also have a custom built RV.

You are not going to find any production RV that will run AC for any length of time on a battery bank. Most would not even be wired to allow it. There are some busses that can run AC for a little while on battery, but not very long, and they are rare.

 

You CAN build a smaller RV that will run AC on battery. I've now helped 3 people set that system up in either a truck (1), van conversion (1), small RV (1). The common thing about all three is that there is not a lot of "conditioned" space. The van conversion used a small residential window unit, and that could run all night but that was it.....And that van had a fairly large battery bank under the bed - I forget now how much, but more than 600 Ah. The truck used a mini-split and around 1000 Ah of battery. The SEER on that mini was in the mid 20's if I recall. The small RV used an auxiliary window unit as well. All of them had solar. All also had engine-driven charging systems. The truck did not have a genset, the van had a portable, the RV had a built in.

 

It is fairly common to use battery powered AC units in commercial trucking. But the systems have limited cooling capacity - eg. they do not cool much space. To the point that most require the curtain to be pulled between the bunks and the cockpit. But all of them can run at least 8 hours on just battery. They typically use AGM batteries.

 

I could see how one could easily set up a B or a van to cool with a highly efficient unit and a good sized lithium bank. In fact, you can run RV standard AC units just fine with a lithium bank, and the Technomadia folks do that - but their bank is relatively small so it limits their cooling time. But one could easily come up with a system to do it. All it takes is money. (I stress LFP here because of its characteristics - light, depth of discharge, etc. But AGMs would work just as well. )

[Jimalberta]

You could however run a swamp cooler with a battery bank without too many problems. Swamp coolers are only effective in dry climates.

[Ray,IN]

I'm just thinking out loud, but I wonder if one of the 12V air conditioners used on semi-tractors, or for RV's would work on a CL B?

 

update: This online calculater will help determine how long your battery will last with a given load; Batterystuff.com

[Jfet]

Yes, we have a well insulated space and a small window unit (rating is about 15.1 IIRC) that draws ~600 watts.

 

I could probably run it for a couple hours at night on our battery bank but certainly not all night.

 

If LiFePO4 gets cheap and mainstream though...

[Daveh]

Well. How is this for timing. http://www.technomadia.com/2015/02/the-almost-fantasy-of-solar-powered-rv-air-conditioning/

[jan50]

Well. How is this for timing. http://www.technomadia.com/2015/02/the-almost-fantasy-of-solar-powered-rv-air-conditioning/

 

Great article - thanks!

[Vicsze]

Thanks for all the answers. Sorry I am late to reply. Been busy lately. Though I always wonder whether the central ac on an RV including even those motorcoach class A diesel pusher can work with engine just as with do with charter buses. Apparently the ones in charter buses as with cars can usually only operate with engine running.

[acampingwewillgo]

Hey....a tad off topic but since there seems to be a lot of knowledge here (as to mini split systems)....I'm wondering, off hand. whether a condensing unit of a mini split system could be laid down on an RV roof, mounting it in the same form as a Solar Panel(with clearance under the condenser? ).......this would certainly allow for mounting the inside unit exactly where I want the extra cooling in the MH. Just thinking out loud here and at the same time wanting a little bit more cooling power on those Hot days while traveling down the road in the cockpit area.

 

PS....not interested in powering with batteries.....I'll be using shore or Gen!

[Jack Mayer]

Yes, it can be done. The biggest issue is vibration and things failing because of it.

[TXiceman]

Someone mentioned an all-electric class b a few days ago, it had a super duty engine alternator and I think.

 

http://www.roadtrek.com/models/e-trek/

My sister-in-law has had an E-Trek for about a month and used it several weekend times off-grid. She had another Road Trek and traded for this one. So far she says it works great. But once spring and summer hit, she will put it to more use.

 

Ken