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Car Air conditioning without Engine Running Answered

Thinkin of running the AC from batteries at times I don't have the engine running.

So- electric motor rather than direct drive from engine?

How long will battery last? maybe need to have a second battery for this?




1 year ago

Suggestion: Get a 12v cooler, leave it in your trunk filled with water bottles and reusable ice packs. They draw about 50W or 3.5A@12V so you could continue running it for an hour or so without worrying too much about flattening your battery, although having a second battery would be a real bonus. You can get batteries with higher capacity than a normal car battery if it doesn't have to be able to provide hundreds of amps to crank your engine and it doesn't matter if it goes flat.

When necessary, pull a cold water/coke/ice pack out of the cooler- it's much more efficient to just cool yourself rather than try to cool the entire inside of your car.

According to Wikipedia, AC consumes about 3KW (or 4HP). That means it draws 3000W/12V=250A. A starter battery has about 36Ah - so it will last 36Ah/250A= 0,144h or about 9 minutes. Bring a lot of extra batteries...

well, shoot. Maybe this is an idea for hybrid cars only.

Also consider most AC compressors are driven by belt, so would need an additional motor, clutch and all...
Might be easier to create an evaporative cooling system instead...

I like that. Maybe even on a separate, solar charged battery.

Why a battery?
Check how cooling was done in the old days.
A pottery pot of suitable size with sand in it.
Everything inside the wet sand was cooled nice until the sand was dry or you left it in the direct sun.
In modern times these designs could be matched with heat pipes in the sand with the hotend inside the car - or by using a fan with solar ;)

I'd guess ACs of electric cars are driven by an extra electric motor anyway as they lack that serpentine belt that drives generator, water pump, AC etc. in a combustion car.