Sep 02

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.

17 Responses to “9 volt battery tongue test”

  1. I did that when I was a kid. Now-a-days, I’d rather cough up for a new battery. ;)

  2. barry.b says:

    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…

  3. dave says:

    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…….


  4. sean says:

    @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” :-) ->

  5. Billy Halsey says:

    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!

  6. Neville says:

    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.

  7. the_rock says:

    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…

  8. Bob says:

    Anyone come across a schematic or instructions or a kit for a hobbyist built tester? (that doesn’t involve body parts)

  9. Spurtz says:

    That metallic taste is chlorine gas. Not too smart, better to use a multimeter.

  10. Matt says:

    I think I found the reason that you need to iPhone trick to find your car… one too many batteries tested this way. ;)

  11. sean says:

    @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.


  12. Sandy says:

    My smoke alarm cherps and I have changed the battery twice and finally change to a lithium 10 year battery. It only cherps when it gets below 60 degrees in the house. When it warms up again, it stops. Strange! Need Help and Sleep.

  13. Mack says:

    I never tried that. A battery can work better by putting one end on your lip (-) and one end on your tongue (+) to really tell if it’s goodly alive.

  14. sean says:

    @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" :-) -> <a href="” target=”_blank”>

  15. Grey says:

    The great thing about 9v batteries is that the contacts connect to each other. I made a run of about 12 of these as a kid. Needless to say i wont be touching them to my tongue again

  16. christian says:

    that hurt bad it scared the shit out of me! (:'{

  17. Keitheroonie says:

    The taste is chlorine gas?? Behave numbnuts :) the taste is down to the dc current and it’s totally harmless

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