Hot Wired

摘要

Last winter I made a heated pad for my transmitter warmer using a surplus 12 volt 7 Ah sealed lead acid battery, the sort used for I/C engine starting. I made four, giving three to fellow flyers to trial. It incorporated a thermal switch, which cut off at 25℃. The idea was to put the pad in the transmitter warmer, connect the 12 volt supply and let it warm up to cut off at 25 degrees switching back on at 15℃. Originally the 12 volt battery was left connected and carried in a tool pouch around the waist, but it was found that the time taken to switch on again once the temperature had dropped 10℃, was longer than the flying time! For subsequent outings the 12 volt battery was disconnected prior to flying. All four pads worked perfectly all winter and we even used them as hand warmers.