Running a 120v a/c unit off starter battery

jrnymn7 wrote:
My question is, would the vehicle's charging system be able to keep up???

I don't see any issue with running your window A/C from a 1000W inverter… Typically 1000W sine wave inverters will have a surge capacity of 2X the rated output. That's plenty to start the compressor in your 5000btu window A/C unit. The real question is; Is your current alternator and DC wiring is up to the task?

IF the alternator output is sufficient AND the inverter is mounted close to your starting battery AND the the power cables (from alternator to battery, and battery to inverter) are sized appropriately, then you're good to go. If your alternator is not able to provide the required continuous current, then replacing it with a high output one is a simple and relatively inexpensive undertaking. Adding a second alternator is a good solution as well, though this solution would be more expensive and complicated, especially if the 2nd alternator mounting componentry is not readily available. Take a look to see what DC Power Engineering has to offer.

As others have mentioned, you will probably be better off powering the inverter from your house battery bank and then run a pair (+ & -) of heavy (2ga or larger) charge cables from the alternator to the house battery (with appropriate fuses and disconnect of course). This will allow you to run the A/C for a short period of time while the engine isn't running, provide a source of 120V AC power in the coach, and prevent you from inadvertently discharging the starting battery if the inverter were to be left on.

By way of example; I replaced my alternator with a 180A model from DC Power and it will effortlessly operate my (8200BTU) roof A/C via my 2000W inverter, plus I can charge my battery bank while underway. I have 2ga wiring from my alternator to my house battery.

Cheers,
-Mark