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Old 08-10-2013, 11:12 AM   #1
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Default easy battery test

Not sure if this will post, but here goes.




http://api.viglink.com/api/click?for...13761474392658
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Old 08-10-2013, 11:21 AM   #2
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Now all we have to do is figure out why that works the way it does.

The ORR.net forum is an excellent place to bounce ideas around.

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Old 08-10-2013, 01:05 PM   #3
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Hmmm -- this I gotta see.

Just now I took two brand-new alkaline AAs (Fry's Electronics brand) out of the package. I'm discharging one of them in a West Mountain Radio CBA II computerized battery analyzer. It showed 1.65 volts with no load. I'm discharging it at 0.5 amperes, and I have set the cutoff voltage at 0.8 volts, after which it will be pretty dead. Currently it's showing 1.48 volts under load.

I'll report back on the bounce tests of the one I'm discharging and the one I'm not.

As a bonus I'll know the capacity of these fairly inexpensive AAs that Fry's sells.
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Old 08-10-2013, 03:59 PM   #4
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Well, I'll be -- it actually works. The dead one bounces and the fresh one doesn't.

I was sure, actually, that I'd prove it wasn't so. I was wrong.

The Fry's AA, by the way, purchased in Dallas about a year ago, delivered just over 1 aH before dropping below 1v. Not too bad.
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Old 08-10-2013, 08:43 PM   #5
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Hmmm -- I think I'll try it with NiMH AAs, which I use in cameras and such.

[Later] Nope, doesn't work for NiMH. Freshly charged and fully discharged, no difference.
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Old 08-10-2013, 10:08 PM   #6
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hmmm....the girls and I tested this theory using AAA (we did not test the batteries using a DMV).

The good battery was purchased just yesterday, the bad battery was dug up from one of the girls bedroom.

The good battery did not rebound as much but was hard to make it stand up (possibly the small size). The dead battery rebounded quite a bit and fell over almost every time...although it did stay up a couple of times....very interesting.

Must do some tests with DMV and then try the bounce test.
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Old 08-11-2013, 07:56 AM   #7
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Guess it's kind of like a hard boiled egg it will spin on it's end a fresh one won't the gook inside the battery hardens up when it's dead?
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Old 08-11-2013, 08:53 AM   #8
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Quote:
Originally Posted by N3LYT View Post
Guess it's kind of like a hard boiled egg it will spin on it's end a fresh one won't the gook inside the battery hardens up when it's dead?
Doesn't have to be on its end, either. Just put it down on its side and spin it. A hard-boiled egg will spin, and a raw egg won't.
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Old 08-12-2013, 07:01 AM   #9
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Consider how the "Dry Cell" works, you have a metal case, an electrolytic "Gel" (or slurry) in the case and a rod of some material in the middle (The positive terminal).

As the battery discharges the electrolytic "Eats" away at the shell, it's the chemical reaction between them that generates the power. So the good battery has a nice THICK shell, but the bad battery, it's paper thin.
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Old 08-12-2013, 09:42 AM   #10
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Quote:
Originally Posted by wa8yxm View Post
... So the good battery has a nice THICK shell, but the bad battery, it's paper thin.
It bounces better because it's thinner? By that theory, an aluminum-foil sphere would outbounce a thicker aluminum shape such as a tea ball.

With all respect, I don't believe it. I think a thinner shell may reduce the coefficient of restitution, not increase it. That is, a thinner shell would bounce less.

Me, I conjecture that gas is evolved inside the shell when the battery is discharged, and that the increased pressure makes it more elastic, like the difference between a deflated basketball and one you've just pumped up.

I can test this. If gas pressure increases within, enough to make it bouncier, the cell should get longer as the pressure pushes the ends out a little. I'm going to mike a new AA, discharge it, and mike it again.

Interesting. The mike shorted it out, of course, so it warmed up a little as I held the mike on it. Started out at 1.9675 inches and warmed enough to get to 1.9680 in the couple of seconds I held the mike on it. After it's discharged, I'll have to let it cool before miking it again.

[Later] Length before discharge, 1.9680. Length after discharge, 1.9730. Longer, but by only about 1/4 of a percent. I don't think that proves anything, except maybe it proves that I'm wasting time and batteries. Oh, well.
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Old 08-13-2013, 06:40 AM   #11
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Well, the shell is THINNER, and... Often this "Thinning" is not uniform.. So I would not say "It bounces better" I would say "It bounces differently".

And the bad battery I took out of the wireless mouse... Remained upright.
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Old 08-13-2013, 08:04 AM   #12
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OK who is going to do the post mortem on a dead battery inquiring minds want to know.
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Old 08-13-2013, 09:15 AM   #13
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Soon battery bouncing will be the latest fad.

Middle schoolers all across America in their Justin Beiber T shirts, out in the hall bouncing batteries off the floor between classes.

Who'd have thought there would ever be a market for dead AA batteries? Collect the Marvel Avengers set, or the Hello Kitty set.

Man, I need some investors before some one steals my idea!!
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Old 08-13-2013, 09:23 AM   #14
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Can you shoot airplanes down with an AA battery?
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Old 08-13-2013, 09:35 PM   #15
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Quote:
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Can you shoot airplanes down with an AA battery?
Don't know about that, but if you filled an airplane completely full of AA batteries it would never get off the ground.

So then you wouldn't have to shoot it down.
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Old 08-14-2013, 11:14 AM   #16
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I haven't tried bouncing this particular AA battery. As you can see, it isn't finished discharging.
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