[brucepick]

Daox, I wonder how you're doing on this. Lots of barely-on-topic material in this thread.

I'm working on a tank type heater on my Civic, not done yet.

HOWEVER, I calculated that running the heater on 12V DC will draw not-too-many amps from my deep cycle battery when parked. I think it came to about .8A for my 850 watt heater. Not enough to heat a cold block, BUT if you connect it after arriving at work it might be enough to keep the block warm till quitting time, without draining too much charge from the battery.

I won't even think about an inverter running off deep cycles to power the heater to heat a cold block. Probably would need a bank of big batteries. I could do the calf but don't know the efficiency losses of typical inverters of the needed wattage rating.