conversion van AC unit on battery

[bigdog101101]

I'm looking at a high top conversion van. Like most vans or large SUV's there is a second AC unit for the rear passengers. Is it possible to run that unit on battery only (without starting vehicle or using a generator). I've read about secondary systems using deep cell batteries. I wasn't sure how to calculate the power requirements to run something like a van's air conditioner.foresight hours.
Or are there better ways to do this. I'm in the Dallas Texas area.

 

[wrcsixeight]

No. &nbsp;Stock AC systems in Vans, the compressor is belt driven off the engine pulleys. &nbsp;You might be able to run the fans to recycle air inside, but blow cold air, no, not without the engine running.<br><br>Some Vans have rooftop AC units. &nbsp;These require plugging into the grid, or running off a generator. &nbsp;If one chose to power the rooftop AC with a 2500 watt inverter on a battery bank, the battery could power it for a few minutes at best, even a large battery bank would be depleted in little time.<br><br>The smallest Window type Ac units are 500 watts or so. &nbsp;These would also drain a battery very quickly. &nbsp;Even if running the engine, the alternator likely could not make enough juice to power a continuous 500 watt load in addition to everything else. &nbsp;If it could, it could not for very long before overheating, or just shortening its life dramatically<br><br>Heating or cooling via battery power is a big challenge, not impossible, but not wise either.

 

[highdesertranger]

no,&nbsp; what's going to turn the compressor?&nbsp; you guy's and girl's are just baiting me into an anti ac rant.&nbsp; I have seen a few ac post lately, that&nbsp;I have wanted to rant.&nbsp; but I am under control no rant here. highdesertranger

 

[Zil]

How do they air-cond Teslas?

 

[bee]

They make A/C systems designed for truckers to use at night for sleeping. &nbsp;They don't work very well and are very expensive. &nbsp;The ones I have seen run off of 4 batteries so they could fit in a van. &nbsp;You have to remember though that they spend all day driving using the engine alternator to charge them back up. &nbsp;Again I am not recommending them, just saying that they do exist and it can be done with a van.<br><br>I just started working at a trucking company and they much prefer APUs which are generators that auto cycle to power everything including air conditioning.

 

[highdesertranger]

on the semis they actually run 2 alternators on those system and like&nbsp;bee said "don't work very well".&nbsp; I believe the small systems have 4 batts they go up from there.&nbsp; did I mention they are very expensive.&nbsp; they have not caught on much.&nbsp; as far as the electric cars look how much your range is cut by running the ac or heater.&nbsp; see I didn't rant.&nbsp; highdesertranger

 

[creationode]

Try a swamp cooler/evaporative cooler unit.<br><br>They use around 75 watts.<br><br>It would produce humidity, though...so have a way to deal with that.<br><br>Just having a cooler of ice with a fan running over to blow the breeze on you, works fine.<br><br>Air conditioners are completely over rated IMO.<br><br>I am also in Texas.

 

[Ziggy Moon]

This is a pretty cool example of a 12 volt Do it Yourself Swamp Cooler Air-Conditioner..... but where to get the ice when needed <img src="/images/boards/smilies/confused.gif" class="emoticon bbc_img"> <br><br>[video]

 

[VanLifeCrisis]

We tried making one of those do it yourself air conditioner/cooler jobs, and i guess here in high humidity, it didnt work too well.&nbsp; If you stuck your hand right over the opening it felt cool but it didn't change the ambient temperature any.&nbsp; Guess they work only in dry environs.<br><br>We didnt try it in a vehicle though, which is a much smaller space...

 

[highdesertranger]

with a swamp cooler you need low humidity for it to work.&nbsp; the lower the relative humidity the better they work. at 10% rh they work great,&nbsp; at 20% rh&nbsp;ok,&nbsp; at 30% rh&nbsp;just as long as it's 95 or below works ok,&nbsp; at 40% rh&nbsp;and above&nbsp;&nbsp;performance drops fast.&nbsp; how ever if you are in an area that they work they are much more efficient and work better imho than ac.&nbsp; highdesertranger

 

[Gus's projects]

So. Some restomods use an elecric ac pump for the cars ac system. To make it work you will have to upgrade your alternator, plug in this ac pump, and if the belt ran anything else, you will have to get a smaller belt.
Okay that was the easy part. Next is the electrical system.
You will want to split your ac electical system. Basically  you will be cutting the rear ac out of the original circut and creating a new circut off your auxiliary battery pack.
That was your first electical hurdle, nexts is what I call the start up surgedraw. you will want to connect some capacitors in your circut to protect your batteries from the initial draw of the system.
After thats taken care of, you will have to decide what limitations you are okay with. The cold hard truth is most batter packs cannot substain an ac unit. Soo if you want it to run during the day, suggest solar. During the night, I would suggest a silent generator. currently I'm looking into making steam generator which should be no louder then a fan. (I got the idea from a nuclear power plant). Then again there is more electrical work for charging balance automatic ect. And there is mounting your generator.
So in short yes it is possible and your best option for space and versatility. However it is probably one of the hardest solutions from a design standpoint.
Still, if your up to the challenge. Its worth it!!
I currently dont use it on my van because I have found that running my ac for 10 minutes during the night gives me 6 hours of sleep and running my ac for 10 minutes during the day in 90 degeee weather gives me 2 hours.
Im definatly running this on my next van build which is about 2 to 3 years out. By that time i should have the steam generator finish

 

[greeneyedggirl]

So. Some restomods use an elecric ac pump for the cars ac system. To make it work you will have to upgrade your alternator, plug in this ac pump, and if the belt ran anything else, you will have to get a smaller belt.
Okay that was the easy part. Next is the electrical system.
You will want to split your ac electical system. Basically  you will be cutting the rear ac out of the original circut and creating a new circut off your auxiliary battery pack.
That was your first electical hurdle, nexts is what I call the start up surgedraw. you will want to connect some capacitors in your circut to protect your batteries from the initial draw of the system.
After thats taken care of, you will have to decide what limitations you are okay with. The cold hard truth is most batter packs cannot substain an ac unit. Soo if you want it to run during the day, suggest solar. During the night, I would suggest a silent generator. currently I'm looking into making steam generator which should be no louder then a fan. (I got the idea from a nuclear power plant). Then again there is more electrical work for charging balance automatic ect. And there is mounting your generator.
So in short yes it is possible and your best option for space and versatility. However it is probably one of the hardest solutions from a design standpoint.
Still, if your up to the challenge. Its worth it!!
I currently dont use it on my van because I have found that running my ac for 10 minutes during the night gives me 6 hours of sleep and running my ac for 10 minutes during the day in 90 degeee weather gives me 2 hours.
Im definatly running this on my next van build which is about 2 to 3 years out. By that time i should have the steam generator finish

My Ford E-350 has a rear AC that is directly coupled to the AC in the engine.  So if one were to wish to run the rear AC, one would indeed need to completely disconnect the rear "AC" from the compresser in the engine compartment, install a second compresser to power the rear equipment, and then have a way to run that compresser fast enough to actually get it to cool the air.  You may actually need a gas engine to run the extra compresser.  It should be noted that in equipment like this, the heating system is ALSO connected to the rear, and that means not just a connection to the compresser, but to the engine heating system as well.  That may be a heavier lift.

Sami

 

[Gypsy Freedom]

My Ford E-350 has a rear AC that is directly coupled to the AC in the engine.  So if one were to wish to run the rear AC, one would indeed need to completely disconnect the rear "AC" from the compresser in the engine compartment, install a second compresser to power the rear equipment, and then have a way to run that compresser fast enough to actually get it to cool the air.  You may actually need a gas engine to run the extra compresser.  It should be noted that in equipment like this, the heating system is ALSO connected to the rear, and that means not just a connection to the compresser, but to the engine heating system as well.  That may be a heavier lift.

Sami

if you were to split the system like you mention, not only would you need a compressor and a way to run it. you would need a condenser (radiator looking thing) and a way to blow outside air over it. you see the compressor does not directly cool the air, it compresses and heats the refrigerant, then in the condenser it cools it to close to the outside air temp then when it goes into the evaporator it gets cold as it evaporates then you blow the air from in the car over the evaporator (another radiator looking thing usually not seen) and that is what cools the air. then the cycle starts over again.

 

[Gypsy Freedom]

after reading the full thread here. dont waste your time with the "ice cooler thing" 1 pound of ice is worth maybe 200BTU's so to be equivelent to a small window ac of 5000 BTU's you would have to be melting 25 pounds of ice every hour.

as for real airconditioning. it is possible to hack the existing system and cobble together something that would work. but it would be a huge project. with expertise needed in mechanics, fabrication, electrical, engineering and HVAC at a minimum.

would be a cool project.. heh heh

it is not cheap, but solar/battery ac is doable.

the last system i did for a friend can run the 12,000 BTU energystar rated window unit a good 6 hours of compressor runtime. to do this, we installed 700 amp hours of firefly carbon foam batteries (use able down to 20% state of charge) then we installed 1740 watts of solar. this was calculated to run the ac during the hot part of the day and still have enough to recharge the battery bank to do it over again. in our preliminary testing during some high 80 and low 90s temps we disconnected half the solar and set the AC to 68 degrees and left it parked in the sun closed up and windshield facing south for 2 weeks. it kept up with it just fine, fully charging the batteries to 100 each day. and keeping it nice and cool inside

of course in a hotter climate where the night time temps were still high enough the air conditioner had to cool through the night it would be different. but we have the other half of the solar to pick up lots of slack. and if it is 100 outside, cooling it down to only 75 will still be very comfortable and save energy

but on a project like this, if you have to ask, you probabl cant afford it. the batteries alone were pushing $4000

 

[gchristi1]

after reading the full thread here. dont waste your time with the "ice cooler thing" 1 pound of ice is worth maybe 200BTU's so to be equivelent to a small window ac of 5000 BTU's  you would have to be melting 25 pounds of ice every hour.

as for real airconditioning. it is possible to hack the existing system and cobble together something that would work. but it would be a huge project. with expertise needed in mechanics, fabrication, electrical, engineering and HVAC at a minimum.

would be a cool project.. heh heh

it is not cheap, but solar/battery ac is doable.

the last system i did for a friend can run the 12,000 BTU energystar rated window unit a good 6 hours of compressor runtime. to do this, we installed 700 amp hours of firefly carbon foam batteries (use able down to 20% state of charge) then we installed 1740 watts of solar. this was calculated to run the ac during the hot part of the day and still have enough to recharge the battery bank to do it over again. in our preliminary testing during some high 80 and low 90s temps we disconnected half the solar and set the AC to 68 degrees and left it parked in the sun closed up and windshield facing south for 2 weeks. it kept up with it just fine, fully charging the batteries to 100 each day. and keeping it nice and cool inside

of course in a hotter climate where the night time temps were still high enough the air conditioner had to cool through the night it would be different. but we have the other half of the solar to pick up lots of slack. and if it is 100 outside, cooling it down to only 75 will still be very comfortable and save energy

but on a project like this, if you have to ask, you probabl cant afford it. the batteries alone were pushing $4000

The absolute maximum  is 1.4kW/m^2, the sun doesn't put out any more than that. What you describe won't fit on the roof of a conversion van. Assume you had some off vehicle panels.

To the original post, the math isn't that hard and kind of fun. Don't forget to include I-squared-R losses. Get to 120V as soon as possible.

 

[Gypsy Freedom]

The absolute maximum  is 1.4kW/m^2, the sun doesn't put out any more than that. What you describe won't fit on the roof of a conversion van. Assume you had some off vehicle panels.

To the original post, the math isn't that hard and kind of fun. Don't forget to include I-squared-R losses. Get to 120V as soon as possible.

no off vehicle panels 4 times 435 watt sunpower panels. they are less than 42 inches wide. 4 of them take up leass than 14 feet of roof space. while this was on a 24 foot (over all length) box van (we even had room for a maxair type fan no over hang at the back and started well back from the slope up from the cad so it would not catch air. no air dam needed.

i have 4 similar panels on my 20 foot over all length short bus( on a van chassis so not much different than a 20 foot van) and 2 side mount swing up (like an awning) panels and that gives me 2005 watts.

while i never said i did the mentioned project on a van conversion, a long van can be 19-20 feet. not sure of the OP's length. also i just posted actual project specs to show what can be done, rather then hypothesizing on what may or may not work. most people would be fine with a 4-6000 btu A/C and as such could get by with much fewer watts on the roof.

 

[greeneyedggirl]

if you were to split the system like you mention, not only would you need a compressor and a way to run it. you would need a condenser (radiator looking thing) and a way to blow outside air over it. you see the compressor does not directly cool the air, it compresses and heats the refrigerant, then in the condenser it cools it to close to the outside air temp then when it goes into the evaporator it gets cold as it evaporates then you blow the air from in the car over the evaporator (another radiator looking thing usually not seen) and that is what cools the air. then the cycle starts over again.

Yes, you are correct there. My van already has a rear condenser in it. I'm not planning to change, was just saying it could be done, but WHY?  As you said, solar AC is so much easier!!!

 

[user 25174]

I live in the Sonoran desert so evap coolers are a welcome means of cooling.
This area has been cooled similarly for centuries, the basic rules are the same, only now we do it better - much better.
A blanket soaked with water stretched across a window facing prevailing wind or breeze.
Most always together with a window for even airflow.
From an early settlers earthen block home, to a turn of the (19th) century3 story Doctors office/home to today's cooling towers atop tall buildings, its changed little in principle.
Unsure of its need it terms of electricity, I've used a portable for years!
Easy to maintain, easier to use with its remote control, and its runs quite cool in my garage shop
$150 I think it cost 4 years ago, even its "footprint" is minimal (approx 20" wide, 14 " deep, and 32" tall).
I'm lookin how to best install one similar in my van.
I just don't do well with heat anywore.
Keith_in_AZ

 

[lenny flank]

The problem with evaporative coolers is that they use a lot of water. You'd need at least five gallons a day to match a 5k BTU AC.

Not a big deal when it's plumbed into the house water supply. Not so easy in a van or RV though.

 

[user 25174]

I own a van with front/rear airconditiong.
I also live in the desert, and found that the rear a/c is useless until .. I drive for at least 45 minutes in summer, and still pretty warm back there.
Tried every (I think) trick I've been told. "Leave it on low always until needed" .. hot air .. "turn off the front" .. big mistake .. back to sweating .. again.
Since new, this vans been this way, and the dealership(s) tell me it works .. hogwash!
My friend, if you find a way to make this useless waste of money work, I'll be the happiest guy in AZ with "working" rear air.

About the evap cooler.
Tried it, and it worked well here in the Sonoran desert.
Just bring plenty of water.

Keith_in_AZ