What are your thoughts on battery heaters. I re-installed my battery heater yesterday after having some problems with it last year. I got into my car this morning, after having a night in single digits and car started right up this morning. Is there anything that I should be careful about when I use it. I know that I should not use it unless it is less than 32 degrees and I thought that there was a maximum time limit of 8 hours for being plugged in.

Since you asked what I thought--I think the warmers are a waste of money and electricity. If you're plugging anything in, plug in the block heater. Additional output from a warm battery compared to a cold battery is miniscule--not enough to affect starting, IMHO. Of course, if it's just a psychological aid for you, then go ahead and do it.

The output from batteries ( lead/acid ) is GREATLY affected by the temperature of the battery...

The best possible situation is you plug in block and battery heaters if you have them....for really cold times...

and remember to leave the glow plugs on a minute or so past when the light goes off... before hitting the starter...

123c, don't see battery heaters on any local vehicles around here. Coolant heaters, engine oil heaters, catalytic heaters (propane or diesel) are the popular things. And those remote starters for the gas jobs (you would have giggled if you had seen me the first time I walked by an empty car that suddenly had the lights come on and start all by itself).

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daBenz - 1970 220D