I am trying to find out how much current draw is on the block heater. It is getting too difficult at work here trying to be able to park near a power outlet. My thought would be to use a 12 volt battery with a inverter to power the heater if the draw is reasonable. My truck is a 97 Ext. Cab 4X4 Automatic.

 

Not sure how much draw but from judging my power bill it is alot. I think it would drain your batttery very fast. I would think a Wabaso or Hot box would work better.

 

I believe it's 750 watts. But I'm not positive.

 

You are correct.
With the average US power rate of 8.14¢ per kWh it will cost you 6.1¢ per hour to run the block heater.
Check your power bill to find your actual power rate and multiply by .75 to find how much it costs you per hour.
Here are the average power rates by state http://www.eia.doe.gov/cneaf/electri...figure7_4.html

A friend tried running his block heater off a very large battery (two people could barely lift it into the bed) with an inverter.
The battery was dead in 45 minutes.

 

I have a 2001.5 and was wondering the same thing about what it took. I bought an energy meter at a local auto and hardware store. I plugged it in and mine took 650-675 watts. Based on our rates here at .1013 cents/kwh it was about 7 cents/hour plus taxes. I don't think an inverter would be very smart.

 

run it for an hour or so and that might warm it up.

 

750Watt-hours (running the heater for one hour) would be 62.5 Ah on a 12V battery if the conversion was lossless.
Recharging it from the vehicle would take rather long (several hours) if you don't want to shorten battery life significantly. You'd need a very big battery to take the draw of more than 60A in cold weather for a long time without being damaged. (Cold cranking amps are meant for a very short time only- like 30seconds IIRC) - The continuous draw as a rule of thumb is about 5-10% of the battery capacity in Ah. So to keep this within specs you should get 600-1200Ah batteries, an Espar heater would cost much less IMO.

AlpineRAM