Dear Heikki,
Suvi will produce more useable warmth that that little heater...
I tried that route last fall.
I hooked up a 12 Volt outlet to a 12 amp hour battery, from a scooter, to save space and weight.
It kicks out a little heat for about 20 minutes, then the battery dies.
I took 5 of these batteries with me, and still didn't have enough juice to stay warm for more than a day.
Honestly, I think a candle would put out more heat...
The heater could not keep up in 38 degree temperatures.
Finally gave up and installed a small RV furnace.
I'm happy now!
Rob
<img src="http://img.photobucket.com/albums/v284/1948rob/small%20pictures/heater1.jpg?t=1189080469">
Waiting for "someday" will leave you on your deathbed wondering why you didn't just rearrange your priorities and enjoy the time you had, instead of waiting for a "better" time to come along...