Testing a Battery - Why Does this Work???

It may work - but that video does absolutely nothing to convice me.

1. The cells were of different type/manufacture - may have been differently shaped and/or of different internal construction.
2. The video has obviously been heavily edited - it would be easy to film each "drop sequence" 20 or 30 times (or however many were needed to obtain the supportive outcomes) and edit out the counter-examples.
3. With the dropping operation being done by hand as shown, it would be very easy to introduce a bias - even unconsciously on the tester's behalf.

Actually, your theories were indeed tested by an EE in the UK who confirmed this with a more controlled experiment. He then went on to dissect them and found that there was a chemical and physical change in the alkaline matrix inside of the dead batteries that accounts for the different mechanical properties when dropped.

http://www.dailymail.co.uk/sciencetech/article-2743595/Want-know-battery-dead-See-BOUNCES-Engineer-reveals-simple-trick-check-cell-lost-charge.html

Now, that might be a hoax too, in which case the Daily Mail should be embarrassed...

how many bounces = 1.5V?

Does it work on dogs??

Works the other way - they fall over and stay down when they run out of oomph. Or maybe it's the same way - can't remember (the video made such an impression ).

Yes but opposite.

No bounce = dead

The author is working now on a video to show how to recognize a egg as fresh or hard boiled in a non destructive way.

speed of spinning difference

chemistry and mechanics

Everybody knows the hard boiled egg determination test.....

I perform it at least once per month. If in doubt spin it about.

Battery bounce test is less reliable than the egg spin.

Lovely, at least he appears to be fully charged!!!

Thanks for sharing!!!

A good dog, will go on and on and on and on....

A dead dog, not so much.

The one battery wasn't completely dead...just the bottom half, which is why it fell over.

'Bad batteries bounce' is alliteration, or beginning rhyme. Hence, 'it rhymes, it must be true'.

In US' slang "bad" means: WOW super good, e.g.

'Bad batteries bounce, but better batteries bounce better.'

I have a battery tester.

We go through tons of AA's.

I'll run an uncontrolled, unscientific experiment, if I remember.

The test is true only for batteries that originally have a flat base.

As an alkaline battery loses charge, it builds up pressure inside due to the production of Hydrogen gas. In extreme cases the metal case can rupture and the leaking chemicals will combine with CO2 in the air to form K2CO3 which you see as a white powder.

Before the case ruptures, it will have expanded due to the internal pressure, and the bit that expands the easiest is the flat end which now becomes convex. The battery will now fall over if dropped from a short distance more readily than will one with a flat bottom.

Some cells are manufactured with a concave base for which the drop test will not work even when the cell is deeply discharged, and others are made with a slightly convex base, and they will fail the test even when new.

I never knew about alkaline batteries building up pressure. This is good information to know. Lately, we've had a run of Duracell batteries that have leaked into our remote controls (stereo, cable tv, etc).

If they just start to leak and die that's fine, they get changed and the device gets a clean.

It's when the device is working fine, no hint of battery demise, and they battery leaks madly for some time before the device stops. Corrodes the terminals and then well ...cuss,cuss, cuss.

Tropical weather doesn't help.

Don't EVER use a dead battery for an oija board cursor........

I treat my batteries far better than that as I want a long life......

A tester is available for a relatively small sum from many places......

maybe this dog swallowed the good one .

Dry cell battery voltage testing without a load is meaningless, sticking an external load on a battery during voltage measurement is subject to a suitable resistor being on hand....not always the case.

A quicker way and very reliable way of quickly checking if a dry cell has or hasn't got any juice in it with nothing more than a multi meter is to perform a quick short circuit current check.

The meter's internal current shunt and the battery's internal resistance are the load.

Measure the batteries voltages first and if there are any that test too low on open circuit don't bother continuing unless your academic interest is piqued.

Connect your meter probe leads to the current jacks of the meter and set the meter range to its max Idc range (normally 10A). Briefly touch the ends of the battery under test with the meter probes, any reading over 1A means there's still some life left in the battery.

The 10A jack is normally fused, make sure you have a spare fuse before doing this.

A non digital (one with a needle) meter is perfect for this job as you get a result much more quickly than with digital meters that dick about auto ranging and cooking while you wait.

I could go on about digital V moving coil meters but that's another rant.

But yeah, short circuit test.

This is totally transparent to me: The good battery is strong enough to stand on its own. The dead battery is dead, and can't stand up. Enough said.