Electrical Guru's, I gotta question:

[Chaz]

Hey guys, I have a little project here and I did not know where else to turn to. It's for my "mini-bus" (OK, it's a '64 GMC van ). I was wanting to run a small inverter to be able to run a small heater OR, a small floor standing Air Conditioner. I have a 110 amp alternator and I was going to put in a couple 6 volt deep cycles. I have been trying to find out if this is a do-able thing before I go looking for components so I don't really have specs on the AC or heater yet. I can get them if it is a "possibility", to do this. If it is, that would also allow me to plug those appliances into a pole when stopped.
I think it will make a cool Toad as I would also like to find the vista windows off of a '60's or '70's Vista Cruiser station wagon and graft them on. It would then have the "hump" like my buffalo.
Thanks in advance!!
Chaz
I hope it is OK to ask you and I'm sorry if I am breaking any rules.

[windtrader]

The variable missing is the length of time you plan to run the device. It sounds like you want to use the van to charge up the battery bank then run the device off the battery through the inverter. A couple 6 volt batteries run in series to get 12v is not going to store much energy to run them for long meaning you need to keep the car running to keep the battery charged up. With a 100amp 12v alternator you'll safely get about 700 watts going into the battery at the most. So it would be very close what goes in and goes out. You'll need to check how many amps can be put into the batteries to know if the alternator and battery is sized to work.

[chessie4905]

Theres an outfit online that can make up as much as a 250 amp alternator using super diodes and such that will drop in place of yours, in case you need more oomph.

[Jeremy]

Using a 12v heater would make a lot more electrical sense than running a 120v one from an inverter I suspect. But you probably would be able to do that for very long without running the engine to recharge the batteries, and if you are running the engine then of course that gives a supply of heat anyway.

Something like a Webasto Airtop is perhaps the real solution you need, and probably equivalent cost-wise to a half-decent inverter - but I realise you would still need an inverter (and a big one I expect) for the AC part of your requirement

Jeremy

Example 12v heater:



Webasto Airtop:

[chessie4905]

I doubt he'll want to spend for an air top even though it would do the job. A small rooftop ac with heat strip and a generator would be the easiest, but just as expensive.

[bevans6]

Let's do the math.  Figure 10 amps at 120 volts for a small heater or 8 - 10K btu air conditioner, plus the depth needed to start an air conditioner.  1200 watts to run, 1800 watts to start, so with say 15% losses you will need a 2,000 watt inverter, which for me is out of the small range and into medium for a 12 v system.   2,000 watts at 14 volts (alternator output running) is 143 amps, call it 150 amps max, around 100 continuous.  Most air cooled automotive alternators are really rated at around 50% of full output for continuous use - they just burn up from overheating and don't last - so figure a 200 -250 amp alternator (you still need power to run the van).  You'd want to be looking at a pretty massive battery bank to run those devices from battery for a long time, but a 200 AH bank would let you run the heater for an hour before a 50% discharge.  If you figure on 200 AH 6 volt batteries, you'd need two of them for a 200 AH bank.  Here is an easy resource:  http://www.vanner.com/estimating-power-requirements/

So for me it's achievable, but not with the alternator you have.  As noted, bigger alternators are available (for pretty much exactly this use in fire trucks, ambulances, etc), and you would have to substantially increase the wiring to the alt. and to the batteries.  I'd run a combined van-house bank of batteries for simplicity.

[Oonrahnjay]

        Chaz - there's technical data above.  The short answer - it's not practical in a vehicle your size.  You don't have enough juice from the alternator, you don't have enough space in a van for the batteries and inverter necessary to run a heater or A/C for more than a few minutes, and -- even if you modify what you have to allow this (at great cost) -- the cost of putting together a useful system would be in the thousands of dollars.  It's just not practical. 

[neoneddy]

Yeah, power generation and sorage is going to be hard.


I think someone above mentioned a webasto for heating, I second that idea. I know your rig isn't diesel but you could carry a small second tank for it. You can even full up with off-road diesel.


AC in a small space like that  wouldn't require much. Look at what the floor model uses in power, or in a very real world sense get a kil-a-watt and measure it directly.

Now the trick most people have mentioned is battery depth of discharge. The golf cart types should not be run down 50% regularly. So when. Figuring battery capacity , you need to double it.

[bobofthenorth]

        Chaz - there's technical data above.  The short answer - it's not practical in a vehicle your size.  You don't have enough juice from the alternator, you don't have enough space in a van for the batteries and inverter necessary to run a heater or A/C for more than a few minutes, and -- even if you modify what you have to allow this (at great cost) -- the cost of putting together a useful system would be in the thousands of dollars.  It's just not practical.

^^^^^^ What he said ^^^^^^

I started to type up that response last night and then got sidetracked.

The other major impediment which hasn't been mentioned is that anything close to 100 amps continuous at 12 volts is going to require a substantial improvement in your drive belt - either multiple belts or a serpentine belt.  What you're trying to do just isn't practical.

[chessie4905]

Back buying a Generator and smallest rooftop ac with heat strip

[Oonrahnjay]

...  AC in a small space like that  wouldn't require much. Look at what the floor model uses in power ...

      I have a "floor AC" in my shop office.  I got it just for temporary since I hope to be moving/downsizing soon but I don't like it much.  It cools down for a few minutes, then -- even though you turn the thermostat down -- it just doesn't get any cooler or if outside temp goes up, the inside temp goes up, too.  Some people have said that the units cool inside air, then draw it through the unit to cool the condenser and then dump it out through the discharge vent. 
      I guess it's better than nothing in a small space but it really doesn't work well, also the power draw is pretty high compared to other small units.

[Oonrahnjay]

Back buying a Generator and smallest rooftop ac with heat strip

       That's a useful, practical solution.

[Oonrahnjay]

Back buying a Generator and smallest rooftop ac with heat strip

       That's a useful, practical solution.

[buswarrior]

Did I miss the intended operating criteria?

Is this for camping or driving?

happy coaching!
buswarrior

[Chaz]

I KNEW you guys would be the best to talk with!! Thank you all for taking the time!!
In answer to your question, Buswarrior - Both. My thoughts were to be able to cool it, via the inverter (and batteries when the compressor starts) while driving with a floor standing AC Unit. An AC unit for a '64 van has to be a generic AC unit fabbed in and the price tag is well north of a grand (WELL north) and a lot of work. And then, to boot, I can't use it standing still. BUT,  if this idea would have been do-able, I could plug into a pole or, possibly my 1000 watt Honda gen, IF it was big enough to push it. I knew the heater would be MUCH less of an issue as the van does have heat (altho it came out with a heater delete plate).
So, that was my big idea.  And it seems you guys saved me a LOT of headache and for that I am very grateful.
BUT, if you should happen to hear of a good way to kill all these birds with one stone (without hanging an AC unit out the window or a generator off the back bumper. LOL ), I'm all ears guys!! And I don't really want a wart on top if I am going to go thru all the work of grafting a Vista Cruiser top on it. (My Big bus will have a "Mini Me".   )
Thanks again!!!
Chaz