DC AC

[ericlp]

Pretty cool thread topic eh?

Wouldn't it be nice to run Air Conditioning on DC?  The toyota prius does it...  I'm wondering, if it would be possible to pull the AC and the hybrid battery out of a wrecked prius, and install that DC compressor into a van...  

My thinking is...  The prius battery is pretty small, what if one had a 200 amp hour lithium battery for AC at night.  I bet it could run the DC compressor though half the night without starting the van for more juice. 

I think it's a cool idea and with so many vans and people living in their vans, why aren't there some 24/48 Volt DC air conditioning units available on the market... you know super high efficient ones. That have Low amperage Starting DC compressors, and I'm sure that with a DC type, they could make a Variable compressor unit, that is, when it reaches it's temp level it just slows down instead of turning off and then kicking on (sucking down super high loads of power like a cheap AC wall one does).  Often these features are found in mini splits to make them so effient. 

One day, we can get our act together and make super efficient small solar DC air conditioners that truely will run off of SOLAR for tiny spaces...

Wouldn't it be cool to have AC that could maintain 80 degree weather in a 95 degree temps by only sucking down 150 watts...  then as the temps creep up the variable compressor could increase wattage or based on battery drain and sun wattage input from the panels, it could adjust itself as to not overload the system while still keeping it cooler inside the van. 

One day I suppose....  We can be truly comfortable in any weather in our vans while not running noisy generators or looking for grid power to plug into just to stay cool.

 

[Riverman]

Welcome to the forum...

I just read that a 6000 Btu DC compressor pulls 49.54 amps on DC.

All night..... nope.

 

[tx2sturgis]

If you are willing to spend the money and have the space, there are electric APU's on the market.

They are used in some OTR trucks. 

They arent solar powered, or scaled down for vans, but the technology and engineering could be, if there was a big enough market.

 

[John61CT]

There have been dozens of threads on just this topic in the past few months.

Practically you need a genny.

Big roof like a schoolbus, only aircon a bit of the living space, can do it solar-only for $5-7000.

Only running the little aircon off the panels during peak sun times, maybe $2-3000.

 

[DannyB1954]

If you are willing to spend the money and have the space, there are electric APU's on the market.

They are used in some OTR trucks. 

They arent solar powered, or scaled down for vans, but the technology and engineering could be, if there was a big enough market.

I used to install those while working for a Carrier Transicold dealership. They are diesel and mount to the heavy frame rails of a truck. They would be a real bugger to attach to a van. A Honda/ Yamaha/ Champion generator in a cargo basket is about the easiest way to go. A 1,000 watt generator can run a 40 amp battery charger. A 5,000 BTU air conditioner uses 35 amps + of 12 volts so to run the AC and recharge the battery in a short time, you would need something like a 160 amp charger, (an 80 amp charger would probably take you 4 hours to do the job).
A Prius has a 1.8 liter engine to run the generator that recharges the battery. That would be a bit large for any van that I know of.

Most anything can be done, but the reason most people are not doing it is, it is more trouble then it is worth.

 

[tx2sturgis]

I specified and was referring to electric APUs and yeah, when I say 'scaled down', I mean that a manufacturer could build them smaller and lighter and make it all work in expeditor vans and motorhomes...IF there was a profitable market.

 

[John61CT]

Towing a Prius would be practical for some rigs.

Very sophisticated genny and House bank, aircon + heating year round.

Get economical local transportation as a free bonus.

 

[Weight]

AND access to fast charging stations in city parks
.

 

[John61CT]

Plenty of small towns, public parking lots, all free.

 

[DannyB1954]

I specified and was referring to electric APUs and yeah, when I say 'scaled down', I mean that a manufacturer could build them smaller and lighter and make it all work in expeditor vans and motorhomes...IF there was a profitable market.

What is an electric APU? All generators that I am familiar with run on gasoline, diesel or propane. The miitary had some that worked off of steam, (and boiler), as they were quiet. They already do make small generators. Many class b units come with them.

 

[John61CT]

Batteries running a small aircon overnight, alt running all day recharges. Google EPU or battery-powered no-idle.

Of course a small genny is required if you're not driving all the next day.

 

[tx2sturgis]

Electric APU means there is no fuel-powered engine running the APU during it's operation.

It is made up of a large battery bank and electric powered heating and cooling for the sleeper berth during a DOT required break. They have some limitations, obviously. 

The large battery bank is re-charged by the oversized alternator or a second alternator on the truck's main engine, when the truck is being driven normally the next day.

Often they have auto-start for the main engine to high-idle and help replenish the battery bank during extended use or in extreme conditions.

California (CARB) and some other states are coming down on common fuel-powered APUs so the market is changing.

 

[DannyB1954]

We have a difference in terminology. My understanding is an APU creates energy. A battery just stores energy so is not an APU.
You will need about 300 amp hours to run a 5,000 BTU AC all night. (mine uses 35 amps 12VDC while running not counting compressor starts). That might be tough to recharge with an alternator, especially if your batteries have a Max limit on how much current they can be charged with.


Onan had an auto start feature available for some of their generators. If battery voltage got low it would start. When I did Transport Refrigeration drivers hated auto start stop Reefers. They could sleep through a constant noise, but when the noise started or stopped it would wake them up. You can get a 1000 watt generator that will run a 5,000 BTU AC and pretty much sound proof it. Yes it will use fuel, but then anything that you use to recharge a battery other than wind or solar will also use fuel.

 

[tx2sturgis]

We have a difference in terminology. My understanding is an APU creates energy. A battery just stores energy so is not an APU. 

Ok...lets not get all tangled up in semantics. An APU (Auxiliary Power Unit) in the transportation industry just means that the main engine is not idling during a layover.....but instead, a collection of parts are used to provide cab and sleeper comfort and power for hotel loads. It gets the power to do just that from the diesel in the fuel tanks...either when the main engine is running an alternator, during travel, or when a small frame mounted putt-putt motor is powering it directly.

Second, we can't 'create' energy, we just move it from form or state to another.

Fossil fuel 'stores' energy. We just figure out a way to convert it to another form of energy: heat, motion, noise, electricity, whatever.
But that's not the subject here.

Electric APU, also called battery-based APU, is just another way around local anti-idle laws in the trucking world.
A 'normal' APU does burn diesel directly when in operation. 

An electric APU, or eAPU, or battery based APU, burns the fuel to power it during the routine operation of the main engine during a normal 8-11 hour driving shift. That electrical energy is routed to the large battery bank for powering the electric APU during a layover.

 

[tx2sturgis]

Onan had an auto start feature available for some of their generators. If battery voltage got low it would start. When I did Transport Refrigeration drivers hated auto start stop Reefers. They could sleep through a constant noise, but when the noise started or stopped it would wake them up. 

When I hauled perishables (temperature controlled) I always left the reefer on 'Continuous' when I was sleeping. Most of us did. And some loads required it. 

'Start-Stop' was used when driving, or when dropping the loaded trailer at a receiver.

 

[tx2sturgis]

Here is a good article that explains the pros and cons of electric APU vs a normal diesel APU.

My original point was that, IF (big IF) there was a market for a smaller electric APU that could work in a van or small motorhome, and be partially assisted with a large solar array, that it might work...the technology is there.


http://www.ttnews.com/articles/apus-diesel-or-electric

 

[rvssaurius]

It seems it's possible a very small generator drive a 5000btu a/c unit... which would probably be good for a small RV / van / ...
I guess that and some solar panels could be a solution... thought not a DC a/c it uses readily available components:

 

[John61CT]

The super-efficient DC aircon units would be worth it **if you were** able and willing to put in enough resources to make it a mostly-solar system, like a rich man's off-grid cabin.

Just saving a bit of genny fuel, not so much.

Some efficient 5000 BTU units can be powered from *some* 1000W gennies. Soft-start capacitor can help.

2000W genny gives more choices.

Victron MultiPlus, MultiGrid and Quattro Inverter/Chargers - check out the PowerAssist feature

 

[ericlp]

Well, it's not just saving the generator fuel, as in a prius, you're still burning the fuel, or if your in a roadtrick with an underhood generator yes, your burning fuel buy starting the ICE (internal combustion engine) prius talk! LOL! Figured I'd give some more funky acronyms here.

But, you also have to considering Store the gas and generator. Plus, let's not forget about the maintenance of the generator and or noise that it makes when running the AC. Most campers don't really want to hear a generator start up to run the AC late into the hot evening hours.

Also, on those 1000/2000 portable generators, you gotta find a good spot to run them and chain em down so no one walks off with your 1000 dollar machine. If there was a feasible way to run the AC off of solar, everyone would do it, but even the 5K watt generators are gonna pull down 45Amps at 12volts. Just not feasible to carry around a sizeable battery bank to handle that load.

So, super efficient aircons WOULD be worth it, buy not having to start the main generator to recharge the battery bank so often. I remember back in the day, refrigerators running off solar was laughable. But, now they are so efficient down to 35~45 watts per hour, you can get buy with a 100 watt panel and a 150 amp hour battery to pretty much run the fridge forever. I know the lowest wattage of a 5K BTU AC unit is about 360 watts, if one could halve that be using variable compressors, it would be almost doable to run a unit like that off of a battery bank that could be stored in a van.

 

[John61CT]

Radically greater efficiency costs a **lot** more up front.

Using the batteries for the aircon will reduce their lifespan by a lot.

Better to just run the aircon straight off the genny, no draw off the bank.