I have a huge flashlight which runs on eight D batteries. I gathered the eight batteries, but I'm not sure if they are all good, and I don't really want to test them all.

I tried testing them all out, two at a time on another smaller flashlight, but this took way too long. Is there any quick way to test if batteries are good?

  • 5
    <comments removed> Folks, if you would like to answer a question, please post it as a proper 'answer' below. Posting answers in comments does not allow that information to be vetted properly. And posting answer in comments makes it look like the author has been helped so people are less likely to post their solutions below. Please refrain from posting answers in comments. Thanks. Dec 17, 2014 at 17:48
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    If it's a 9V battery instead, try licking it! It's fun! Dec 17, 2014 at 21:20
  • Not a life-hacky way, but you can buy all-purpose battery testers for about 2$ on eBay/Aliexpress/Amazon/etc. Search for "battery tester". I doubt there's any simpler and faster way of testing.
    – Neinstein
    Oct 15, 2017 at 12:49

4 Answers 4


You can test if your batteries are dead by dropping them on a hard surface - just 5cm worked for me.

If your battery is alive, it will not bounce, and a discharged one will. Why?

A non-rechargeable battery begins with zinc powder mixed into a gel containing a manganese dioxide powder. As the battery discharges manganese dioxide powder changes to manganese oxide so the granules start to bond chemically. This packed-sand consistency reduces the anti bounce effect caused by the original gel mixture.

Source: Lifehacker

Anti bounce is caused because the gel inside moves slower than the battery, so as the battery tries to bounce back up, the gel inside is still falling and stops it.

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    Does it matter how you hold the battery when dropping it? I can imagine it's hard to see if the battery bounces, if you drop it on the shorter side (negative) and it will end up laying on the longer side.
    – Alex
    Jan 8, 2015 at 10:48
  • I think drop onto the flat (—) side.
    – Tim
    Jan 8, 2015 at 15:36
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    And can dropping it ruin it somehow? Can it hurt the manganese stuff and make the battery go bad/die?
    – msb
    Jan 19, 2015 at 6:39
  • @Msb doubt it...
    – Tim
    Jan 19, 2015 at 14:44
  • @Tim Pity that you removed a meme (which comes from the same source), but I think it helps more people to find that Q&A solution page easier via different image search engines.
    – kenorb
    Jan 24, 2015 at 11:49

I touch "+" with tip of my tongue. If battery is dead, it is tasteless, otherwise it's like a lemon. Don't try it with 9 Volts or more - it's painfull. 1.5V is ok.


Also you can test your battery if you're not sure by voltmeter. Some bouncing bateries may be suitable for use.

  • Please limit your answer to just one solution. By having multiple solutions in one answer, if your answer is marked as accepted, the rest of us have no way to know which solution was the one that worked. Recommended reading: Lifehacks Manifesto Feb 5, 2016 at 21:44

You can make one with a bulb/LED and a paper clip...

Use the bulb from the flashlight or a LED.

  • set the battery on the positive end of the battery to be tested.
  • take a paper clip and bend it into a makeshift "C"
  • touch one end of the paper clip to the negative (flat/bottom) end of the battery.
  • touch the other end of the paper clip to the bulb side.

You may need to use adhesive tape to help you, or get a friend / third hand to help hold the items together to make a good contact.

If the battery is good, the bulb will light up (if correct connections are made on the battery AND bulb). The brighter the bulb, the more juice the battery has.

NOTE: If the bulb doesn't light up right away, make sure you fiddle with the connections a bit before you discard the battery.

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    If you have a flashlight bulb, why not just put them is the flashlight?
    – Tim
    Dec 17, 2014 at 17:01
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    he has 8 of them and wants to know which ones are bad... all 8 are needed for the flashlight. This process of elimination will help him determine which ones need to be replaced out of the batch.
    – Phlume
    Dec 17, 2014 at 17:10
  • Ahh I see, yeah that would work then :)
    – Tim
    Dec 17, 2014 at 17:11
  • Any explanation on the DV folks?
    – Phlume
    Dec 17, 2014 at 19:26
  • Not very hackish is it... I didn't DV btw?
    – Tim
    Dec 17, 2014 at 19:27

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