14.8v would be a bit high for a running car. Most batteries are 12.2-12.6 charged, and 13.5 or so for running. Lower with things like headlights, heater, stereoect runnning.Highest I've ever seen is 14.2 without anything running, and that was after upgrading to a 130amp alt, where the old was 55amp.
Some 12v electronics are not regulated, even when "designed" for automotive use. If the voltage range isn't higher then 12v, and it isn't regulated, your going to burn something up. Also, with a 12-24v range, the higher input you have, generally the less taxed the regulators are. To a certain extent, it is better to be slightly over voltage, then under, as long as your in the acceptable range. I am guessing something in the charger shorted, or your pulling too many amps on the cigarette lighter socket.
In my station wagon I can charge 4 3 cell 1800's at a time, all day long with the car off without worry about the battery going dead. 2 of those run off of the cigarette lighter socket, shared between my stereo, cellphone charger, and both chargers in the rear door. The other two are run under the hood with clips.
Your battery should be rated for 650cold cranking amps or more. Deep cycle discharge should be higher then that. Figure 2-4 chargers at 12.6v's, and 4 amps each, 36-72 amps an hour, it should take me over 8 hours under full load to run my battery dead. I also generally charge at .3 to .5 amps if I'm not in a hurry, and 1.75 if I am. So basically, I should be able to charge 4 battery's for a full day of flying before my car battery runs dead. My dx6I transmitter batteries won't even last that long.
If your charging large cells at higher voltage, like with lithium ion, it will draw significantly more then that.
Most regulators will work much harder as voltage drops. With car computer electronics, most things would run for 15 seconds or so at 8v's before browning out, but would pull much more amprage through all of the curcuits. Making it work harder will burn it out quicker, especially at lower voltages. My old ford uses a larger power consuming starter motor, and it will crank over well enough to start down to about 8v's. Lots of newer cars run much more efficent starters, I know one guy that couldn't roll his windows up and down after leaving his headlights on, but it did start. So if you were running your battery lower then the 12v's the charger was rated at, you were overstressing that charger.
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