Funny…..
I got a good chuckle out of the hand warmers for the batteries……
The fact is most people don’t realize cold batteries work great except in extreme temperatures and the only thing you lose with cold batteries is capacity or battery life. Some detectors are advertised as having an operating temperature range of 4 to +122 degrees F (-20 to +50 degrees C) and some well known battery manufacturers say -18 degrees C to 55 degrees C which is pretty cold…..
Battery life doesn’t even begin to drop off until about 20 degrees Fahrenheit and will still work fine close to about 5 degrees Fahrenheit and even then a detector wouldn’t be affected in terms of performance they just dont last as long.
Rechargeable batteries are less prone to cold but don’t last as long to begin with so cold weather may wear them out faster. Some Lithium’s will work -40 F anything that says Heavy duties are no good even in warm temps.
If you store your batteries in the cold you can actually gain voltage as they ‘warm up’ by being used but if you take your batteries from a warm car or house with your detector it shouldn’t be an issue unless its really cold and I don’t know why you would be detecting with the temperature below 5 degrees F Brrrrrr….
All you need is a good quality battery for cold weather but most will work well.
Sandman, what do you mean that they need to be warm to work properly and supply the correct voltage? I found this missleading for the newbies

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If I am wrong someone please fill me in.
Thanks
The Falcon