i do not own a forced hot air preheater like the one mentioned previously but a question posed to thoes that do..
i am having a hard time thinking that is is a good idea to power a unit like theese off of you aircraft starting battery. first the battery on an aircraft (presumably at a remote airfield without services and or 110v power nearby) which is already cold from the weather(otherwiese why would you be preheating) is at a very serious disadvantage when tryng to get your fan started. second the battery is not very big, in fact i think that they are just barely enough to do their job, and i know the reasons.. weight, ballence, acid loose in and accident etc which i do not dispute. third, this situation is the worst opperationaly because you are going to drain down the battery some ammount right before it has to put out the most it ever will under the worst sircunstances a battery can face.
am i missing some portion of the operation of theese heaters? do you guys carry/procure a seperate battery for this opperation? or is it just the worst way to heat at a remote airfield except for all of the rest which my not be possible at all. i assume that it takes a while to acctually get the engine up to a resonable temp which i am assuming is 15 to 60 min depending on outside air temp and weather you are employing thermal cowl and prop covers etc. just my thoughts on this particular type of system and i am only posting this to see what others have experienced and or their procedures to prevent over draining their battery on a cold day.