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9 volt battery tongue test
September 2nd, 2007 by 
sean 
For a quick way to tell if there’s charge left in a 9 volt battery, briefly touch the contacts together with your tongue. If there’s juice in the battery you’ll get a tiny shock (and a nasty metallic taste). It’s not enough voltage to hurt you but it’s definitely not pleasant and you wouldn’t want to test a bunch of batteries this way.
I can’t remember exactly who showed me this technique but I’ve used it for years in checking gadgets like smoke detectors and guitar tuners. Sometimes the battery truly is dead but other times it’s just a matter of it having been jarred out of place and needing to reposition it so the contacts line up properly.
lifehack
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September 2nd, 2007 at 3:18 pm
I did that when I was a kid. Now-a-days, I’d rather cough up for a new battery. ;)
September 2nd, 2007 at 4:01 pm
What’s next I wonder:
licking cane toads perhaps?
if so, there’s a few million around here you can have if can catch them…
September 2nd, 2007 at 7:01 pm
now that you got this one down let me tell you how you test an electric fence….
don’t touch it! walk up, pull your trousers down, aim…….
;)~
September 2nd, 2007 at 7:21 pm
@brandon- yes i suppose we’re ghetto like that. i just bought a bunch of new floodlights for our office and you can bet i’ll be unscrewing all those and taking them with us when we move in december :-)
@dave - “don’t whiz on the electric fence” :-) -> http://www.electricfencewhiz.ytmnd.com/
September 3rd, 2007 at 1:49 am
My dad showed me that one when I was about 4 or 5. I used to love doing it. The little scientist in me even tried it with C and D batteries, but no go. The gay man yearning to break free, though, did discover that putting 2 D batteries in my mouth at the same time and saying “Hello, I’m Barbara Walters” made for a surprisingly good impersonation!
September 3rd, 2007 at 7:11 pm
Hey what happened to spending a few bucks for a battery tester? lol
These days the only thing I use a 9-volt battery for is my smoke detector and boy do I know the battery is dead as the detector makes a high pitch cherp every minute.
September 24th, 2007 at 12:42 pm
I’ve been testing 9V batteries like that for over 50 years and it works (qualitatively) just fine. You can easily check 1.5 V batteries too — just wet your finger to touch the other electrode. The effect isn’t as strong, but you definitely can tell a dead battery…
October 3rd, 2007 at 9:32 am
Anyone come across a schematic or instructions or a kit for a hobbyist built tester? (that doesn’t involve body parts)
November 21st, 2007 at 1:03 pm
That metallic taste is chlorine gas. Not too smart, better to use a multimeter.
September 10th, 2008 at 1:02 pm
I think I found the reason that you need to iPhone trick to find your car… one too many batteries tested this way. ;)
September 10th, 2008 at 1:40 pm
@Matt - no doubt. those braincells are long gone and clearly electroshock, while appropriate in some situations, is no cure for being navigationally challenged and forgetful.
sean