I just ordered the katz 80W heater this morning. The bad thing is, I don't think its going to work very well now that I did the calcs (of course AFTER I ordered it).
First, I assumed the whole battery was made of water. I know this is not correct, but we're just getting a ballpark figure here. So (10-1/4" x 6-13/16" x 8-7/8") = ~2.6 gallons or 21.7 lbs.
80W heater will give me 80Wh in an hour (duh
) = 273 btu.
273 btu / 21.7 lbs = ~12.5 degree F increase.
Since my block heater is sized to heat up as quickly as possible, I only have about an hour to preheat. So, it looks like I may need some additional heat somehow, and insulation is going to be very important.