12V (DC) vs. 110V (AC)

I think I know the answer, but I thought I would throw it out to you' all because someone probably "really does know".

If wattage draw was the same, would there be any electrical current draw differences between a 12 V appliance and a 110 V?

I just left a company where I had an APU and a large inverter - I think 1800W. I had a small "dorm style" fridge which was rated at 6 amp. Well, the inverter would "kick out" for no apparent reason, and I had one of the mechanics tell me it was because of "that huge fridge". Long story short, I spoke with ThermoKing (Tri-pak unit) and they didn't think it was the fridge. They said to check the connections at the battery and the fuse link. Anyways, another time maintenence checked and found some to be loose. After that, no problems.

Now that I explained that, if I am right, 6 amp. should be approx. 660 Watts # 110V. Of course 6 amp. should be "peak" draw since the fridge wouldn't always be on. I believe that I'll be allowed to buy a large enough inverter to cover it and more, and the company will install it. My concern is that I will no longer have an APU to charge the batteries, so I will be either drawing from the Altenator (no problem) or the batteries (?).

I'm soon to be getting into a truck with out an APU. With the above fridge, should I be able to not idle for the night? Please assume that I would use other electrical draw items while idling - i.e. microwave, coffee maker, TV, etc. - so would probably have fully charged batteries before "shutting down".

Sorry for the longer post, but I wanted to provide enough info. if someone can help. I asked some specific questions, but maybe I only need a general answer to a general question. With fully charged batteries, and all other electrical items turned off, should I worry about running a 6 amp. fridge for the night. The last thing I want is to wake up to is "click click click". Last thing, I realize that factors like winter, starter and engine and battery condition will all be factors.

Thank you in advance for any constructive help! Take care, be careful out there, and have fun!

 

Thank you all for the quick replies:

1) Dutch - I'm afraid you missed something, or I didn't explain it right. I have a 110V fridge that is rated at 6 amps. I believe that means that it would draw - 110 X 6 = 660 Watts. I can't convert the 110V fridge to 12V.

2) Pharm - I am wondering about a switch or having the fridge "hot" so that it is off when the ignition is off? I don't mean to scare you, as much as I want more of an idea of how far I can use these batteries before I hear that "click click click" - been there, done that! I like your ideas to turn it off.

3) Red - I like the insulation idea! Reminds me that the exhaust from my previous bunk heater was low level as the fridge. Blocking that might mean alot - frankly, with the APU, I didn't need to think about these things! Unplug, turn off, or wire "hot" to the ignition so it is off.

This brings me full circle to - Dutch. All of the OTR trucks that I have driven have had a 12V outlet in a cubicle that a cooler or fridge could go. Also, they either had switches on the dash for "refridge" or "option". The first I assume was wired to the above outlet, the later, I don't know other than possibly being wired to other 12v outlets in the truck - I can think of at least three others. Do you see it as a big deal (i.e. expensive) to switch that 12V outlet to a 110V connection connected to one of those dash switches?

 

Now you bring up another thought, Pham. That is, let's say you need 1500 Watts to cover your needs. Would there be any advantages to having a 2500 Watt Inverter compared to 1800?

Seems to me that it wouldn't matter, but I really don't have a clue.

My biggest concern right now is draining my batteries, and I don't think the Inverter would matter (as long as it covered the minimum voltage) - it would only cover the conversion from DC to AC - right???