I have a basic electric system, I don't run anything extra that is not vital to engine go"ness" except sometimes a sterio. I am looking at getting a quickAir2 and a 5gal tank. they draw 30 amps. Will this hurt my electrical system if I only use the compressor when the jeep is on. I run a Red top battery, I am looking for input, becaue I have no Idea about electrical systems, Thanks

My Guess, I doubt it but I'm no expert either. How about installing an Amp and or volt guage at the same time? I know there not the same thing, but it should give you an idea if your battery is about to crap the bed

You will be fine running that at 30 amps if that is all that is on. You should still have reserve left even. Most staock alternators are around 50-60 amps. Yours is a newer vehicle, that info should be in the owners manual if you have it. Just make sure your switch or connections can take the rated current. A cigarette outlet will blow fuses on this-they are usually fused at 20 amps.

Thanks for the input. I always like to learn new things about the Jeep and the electrical system is a good place to pick up some info.
On board air here I come.

Let's clarify here. As far as electrical goes, your Jeep has two "sources". The first is the alternator, which puts out a supply when the engine is running. The second is your battery, which is recharged by the alternator.

The real heart of your question is about electrical economics.

You can actually run higher loads than what your alternator supplies, but the catch is FOR HOW LONG.

For example, say you have a 60Amp alternator, and you want to run a 30 amp air compressor, a 30 amp stereo, and a 30 amp set of lights. That will work, but you will start to eat into your battery's reserve charge, because you are using more electricity than it can replace. This is not bad in and of itself. As long as you reduce the load before you completely tap out the battery.

On average, you're never going to run your compressor, lights, and stereo together for more than 10/15 minutes or so at a crack. As long as you give the alternator sufficient time to recharge the battery before shutting down the engine.

Also a note listed above to clarify:

A volt meter will show you what the charge is currently on your electrical system or if the engine is not running, what the charge is on your battery.

An Anmeter (amp meter) will show you load being placed on the electrical system.

Neither will tell you the whole story, you need to look at the system as a whole, considering time as well, and then you can make some informed decisions.

'91 has the 75 or 95 amp Nippon Dinso alternator, you will be just fine on the air kit.