My 1993 came from the factory WITHOUT A/C so finally found something that I can install that is not a arm and a leg price wise..It's a electric AC truck parking cooler..they draw about 30-70 amps when running..I know my alternator when I replaced it was a 120 amp one...so my question is would the alternator handle the draw of say 70 AMPS running the compressor for long periods of time or not? I live in AZ where it runs 100-120 all summer long so AC is a real issue..on the other hand the grid heaters come on twice a year lol.
This AC units are used mostly on Semis to keep cool at night without the engine on so run on batteries but figured If I can run it off the alternator when driving then it should run just fine or off the battery that the alternator is filling all the time while running the engine.
Thoughts, comments suggestions are very welcome...
PS when my alternator broke I was pulling 12000 pounds down I 5 in CA on the way to AZ..it drove the rest of the trip 700 miles with no alternator so I know the truck on it's own uses hardly any juice once running

 

I would get a separate battery and a diode separator to avoid running your starting battery down at night. I have a pair of extra fans blowing air through the condenser on my truck that draw about 40 amps when the compressor kicks in. The stock alternator handles it just fine.

 

I will actually only be using it to run while driving the truck so no chance of running the battery down at night..UNLESS I forget to turn off when I get out lol..Glad to hear you can run your 40 amp draw well..in looking I find most big draw items are electric seats, windows and AC and I have none of those so the 120 amp alternator maybe gets 10 amps used ..when the high beams are on, LEDs as well so very little draw

 

If I'm correctly remembering my basic electricity (which I learned at Ben Franklin's knee as a youngster) your alternator is capable of 120 amp output as needed, but will furnish no more than actually needed as the batteries demand it...Therefore it seems that in the desert heat your alternator might be putting out half its rated capability in a 100% duty cycle...Are you sure you want to trust that load to a possibly decades-old alternator?...It just seems a lot to ask...If I was to install that system I would use Edwin's advice for an isolated extra battery even though it creates extra weight and space requirements...

Results are based on forethought......Ben

 

I agree with you..just that want to make sure the output would not tax the alternator even if I am using extra battery but from what I gather so far they are capable of around 80% all the time without much harm to the alternator. so it should be fine since the rated capacity is 120 and even at full blast AC would never pull more then 80 amps and my truck due to no load really maybe another 10 at most with LED high beams and radio..WHICH is good!
I run solar on my place and have plenty of deep cycle 6 volt ones around and can throw a couple by the AC on the flatbed to run and then just a charge wire from other battery with the isolator as he mentions...
I appreciate your well thought out comment!

 

The alternator has a regulator which limits the voltage to charge the battery. Mine is set at 14 volts AT the battery. The amperage it puts out is whatever is required of the accessories and battery while maintaining that 14 volts up until the Resistance and RPM of the circuits involved begin to reduce the voltage. E=IxR and derivative formulas.

You're right however that an old alternator may strain under the load. But until that happens I'd just drive along and if the alternator quits then turn off the A/C until you get home and fix the alternator. All the power you need is to hold the FSS open. and you can drive a long way just running a few LED lights and that stupid thing.

In another life I was an electronics engineer.

Edwin

 

Well I screwed up my original alternator so 1 Had to pull my 5er without a alternator 700 miles which it did just fine 2. Have a new alternator...But I think I will be putting 2 6 volts deep cycle in flatbed to run the thing and then a charge wire top it from the other front battery with a isolator like someone suggested...2 or 4 AWG depending on feet

 

Down here lots of parts trucks pop up.

 

Keep us posted about how it does.

 

it took me3 months to find a door and it wasn't even from the truck but was the same from a different vehicle

 

I will, I see they sell the ones for semis thing maybe a bit better for 2 grand all over he place..I'm thinking this is like the chinese diesel parking heaters as compared to the German ones that cost 6 times as much...But will post my results of it once installed.
PS I have 3 chinese heaters and they work great!