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EEVblog #508 - Can You Test Battery Charge By Dropping It?
Posted by
EEVblog
on 15 Aug, 2013 09:15
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Can you determine the charge of an alkaline battery by simply dropping it and see how high it bounces?
A followup to the KipKay video
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#1 Reply
Posted by
ddavidebor
on 15 Aug, 2013 09:36
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Mmh morning video niceeee
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#2 Reply
Posted by
adam1213
on 15 Aug, 2013 10:47
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The result you get might be correct. However I am not convinced by the testing method. Dave - thanks for doing a video about battery bounce vs charge.
Areas that could be done better:
- Do a blind test where you have a group of batteries of unknown charges, drop batteries, rate the charge based on the drops then compare it with a multimeter / see if you can rank the charge based on the how they bounce, record it then compare it with the actual result.
- Drop the batteries in the same way from the same height. e.g. use a line to drop the batteries from. Preferably make a device do the dropping. In the video
- Show that a given battery normally bounces in a certain way.
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#3 Reply
Posted by
Citizen
on 15 Aug, 2013 10:56
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OMG it is not rocket science...
Charged batteries have more electrons=> more weight,
Empty battery=>less electrons=>less weight.
You can also spin batteries to check if they are charged:
If it is full with electrons, then the battery will not wobble, since the mass is distributed equally through he whole? battery.
In case it is discharged, then it will wobble, because the electrons will shift the mass center...
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Why would anyone think this is about weight? Weight changes would not change the bounce.
It's clearly a damping effect due to the change in physical properties affecting the mobility of the stuff inside, which change how much mechanical energy it absorbs.
I bet if you opened them up you'd find the bouncy one less goopy than the other
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#5 Reply
Posted by
EEVblog
on 15 Aug, 2013 11:03
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The result you get might be correct. However I am not convinced by the testing method.
I said it was deliberately a very quick unscientific test, just as a go/no-go to show if it's true or not, or marginal.
From the result it is almost certainly true. I was expecting it to be marginal, but it's a fairly big difference in bounce.
I dropped some other fully charged ones and it appears consistent, as you'd expect.
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#6 Reply
Posted by
dr.diesel
on 15 Aug, 2013 11:05
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I bet if you opened them up you'd find the bouncy one less goopy than the other
Perhaps some of the same reason dead batteries are prone to leaking as well.
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#7 Reply
Posted by
EEVblog
on 15 Aug, 2013 11:08
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OMG it is not rocket science...
Charged batteries have more electrons=> more weight,
Empty battery=>less electrons=>less weight.
To quote Doc Brown - "weight has nothing to do with this"
It is not the weight, it is a change in the dampening effect of the changed chemical reaction and hence composition in the battery, as I mentioned in the video.
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#8 Reply
Posted by
tinhead
on 15 Aug, 2013 11:14
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Why would anyone think this is about weight? Weight changes would not change the bounce.
right, it is not weight directly. An discharged batt have (actually you cant "have" dark matter, you can only "bind" it) less dark matter (which is due changed potential and/or amount of electrons), so the influence of dark energy (on the gravitrons) is bit higher and the batt can bounce more/higher.
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#9 Reply
Posted by
EEVblog
on 15 Aug, 2013 11:16
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- Do a blind test where you have a group of batteries of unknown charges, drop batteries, rate the charge based on the drops then compare it with a multimeter
Using a multimeter to determine a batteries charge level is a very poor way to do it.
- Drop the batteries in the same way from the same height. e.g. use a line to drop the batteries from. Preferably make a device do the dropping. In the video
I will do that, but I need some bits and more time.
- Show that a given battery normally bounces in a certain way.
I can confirm fully charged batteries bounce to roughly the same height.
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#10 Reply
Posted by
Citizen
on 15 Aug, 2013 11:17
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Lol. i was joking:))
BTW a charged battery has as much electrons in it as a discharged one;)
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#11 Reply
Posted by
EEVblog
on 15 Aug, 2013 11:24
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KipKay's video is a complete ripoff of this one done a month ago:
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#12 Reply
Posted by
Wytnucls
on 15 Aug, 2013 11:32
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You could also carefully recharge the depleted battery and see if it stops bouncing.
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#13 Reply
Posted by
Psi
on 15 Aug, 2013 11:56
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It's probably to do with the reflected shockwave being somewhat absorbed vs propagated throughout the battery chemicals.
A better question is, if you do it repeatedly will the absorption/propagation rob a full battery of charge or recharge a flat battery.
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#14 Reply
Posted by
ddavidebor
on 15 Aug, 2013 13:05
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No
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#15 Reply
Posted by
Wytnucls
on 15 Aug, 2013 14:00
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When the battery discharges, hydrogen gas is formed, increasing the internal pressure in the battery. The spongy KOH electrolyte then acts as a spring at impact, with a higher recoil than in a charged battery.
With the aid of a micrometer, one may be able to measure a slight difference in battery overall length depending on charge condition.
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#16 Reply
Posted by
lewis
on 15 Aug, 2013 15:35
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Is it April 1st already?
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#17 Reply
Posted by
LaurenceW
on 15 Aug, 2013 16:29
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My dad dropped the car battery from our old Austin Marina on his foot, once. That was flat, but I don't think it bounced that much. I did learn a new Anglo-Saxon expletive, however.
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#18 Reply
Posted by
KedasProbe
on 15 Aug, 2013 18:25
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Maybe you can drill into one at the top to let the gas out.
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#19 Reply
Posted by
hammy
on 15 Aug, 2013 20:36
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... as I mentioned in the video.
Before the video you bounced the batteries and then you discharged the two who bounces better. Then you marked them black and made the video.
No need to fake the video. You
sorted the batteries before.
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... as I mentioned in the video.
Before the video you bounced the batteries and then you discharged the two who bounces better. Then you marked them black and made the video.
No need to fake the video. You sorted the batteries before.
For next video, someone needs to go to the store and get fresh pack of batteries and film it all on one go. From buying to testing to conclusions. Please get James Randi as your audience so there is no trickery. After that someone will determine that the people at the store were actors and it was all faked.
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#21 Reply
Posted by
IanB
on 15 Aug, 2013 20:51
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So is nobody going to mention that dropping batteries onto a hard surface is a really bad idea?
With NiMH you can certainly damage the internal construction and cause a permanent loss of capacity.
With alkaline batteries there is a danger you could weaken the seal and make the battery more prone to leakage.
With carbon-zinc batteries you could snap the positive carbon electrode and kill the battery.
A good rule for all batteries is to treat them gently and do not subject them to mechanical shocks.
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#22 Reply
Posted by
firewalker
on 15 Aug, 2013 21:46
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Take two metal cylinders. Fill them with water. Freeze the one. Drop them.
Alexander.
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#23 Reply
Posted by
Psi
on 15 Aug, 2013 22:06
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No
You can't say that unless you've actually tested it.
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#24 Reply
Posted by
EEVblog
on 15 Aug, 2013 23:14
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Before the video you bounced the batteries and then you discharged the two who bounces better. Then you marked them black and made the video.
No need to fake the video. You sorted the batteries before.
I assume you are kidding, right?
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So is nobody going to mention that dropping batteries onto a hard surface is a really bad idea?
With NiMH you can certainly damage the internal construction and cause a permanent loss of capacity.
With alkaline batteries there is a danger you could weaken the seal and make the battery more prone to leakage.
With carbon-zinc batteries you could snap the positive carbon electrode and kill the battery.
A good rule for all batteries is to treat them gently and do not subject them to mechanical shocks.
I'm not being a wise-ass here, I feel I have to say that because my comment may appear snarky, when I'm being sincere. Is the small shock of dropping a battery (really a cell, but I won't go there) those few cm really a problem? Aren't they subject to far worse treatment in packing and shipping, and in use in various devices?
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Gives a whole new meaning to "dead cat bounce"
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#28 Reply
Posted by
IanB
on 16 Aug, 2013 06:46
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I'm not being a wise-ass here, I feel I have to say that because my comment may appear snarky, when I'm being sincere. Is the small shock of dropping a battery (really a cell, but I won't go there) those few cm really a problem? Aren't they subject to far worse treatment in packing and shipping, and in use in various devices?
Sure, just dropping from a height of 5 cm or so as David showed won't cause much of a shock. But reading the subject line without context is alarming. I can state from experience that dropping a NiMH cell from desk height onto a hard floor is certainly able to damage it.
Lest anyone be tempted to increase the drop height to see a greater bounce, I caution against it. I know an alkaline cell is not an NiMH cell, but given that alkaline cells have a tendency to leak and ruin electronics it would be wise not to take chances.
About packing and shipping and abuse during transit, yes this is actually a concern, although hard to prove or quantify. Bad handling between factory and consumer is something that may increase the risk of leakage when the battery is in your hands.
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#29 Reply
Posted by
99tito99
on 16 Aug, 2013 07:05
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Poke a hole in the discharged bat to relieve the pressure, then check the bounce.
Cheers, Mark
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#30 Reply
Posted by
ddavidebor
on 16 Aug, 2013 08:57
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No
You can't say that unless you've actually tested it.
If i've understand the question then is no. That kind of things just don't happen.
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#31 Reply
Posted by
nitro2k01
on 16 Aug, 2013 09:36
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If i've understand the question then is no. That kind of things just don't happen.
What kind of thing just doesn't happen?
You do realize a chemical process happens while the power is consumed right? A fresh alkaline battery consists of zinc powder for the anode and manganese oxide (MnO
2) for the cathode. When the battery is dry, the anode becomes ZnO and the cathode another manganese oxide (Mn
2O
3). It stands to reason that the final ZnO is no longer a powder, but mostly a big solid lump, which is much less shock absorbent. But don't take my word for it, you could actually open a fresh and a dry alkaline battery and investigate the consistency of the materials.
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#32 Reply
Posted by
nitro2k01
on 16 Aug, 2013 09:42
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Right, you were answering Psi's question in the post above the "no" post. Well, it might actually serve to discharge the battery quicker. How? By temporarily or permanently damaging the integrity of the separator between the anode and cathode and help the self discharge happen more quickly.
I don't see how mechanical impact could recharge the battery. Maaaybe if it rearranged the anode and cathode materials such that an unused part of the chemicals could be used. Even so, that effect would be negligible at best.
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#33 Reply
Posted by
ddavidebor
on 16 Aug, 2013 09:44
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If i've understand the question then is no. That kind of things just don't happen.
What kind of thing just doesn't happen?
You do realize a chemical process happens while the power is consumed right? A fresh alkaline battery consists of zinc powder for the anode and manganese oxide (MnO2) for the cathode. When the battery is dry, the anode becomes ZnO and the cathode another manganese oxide (Mn2O3). It stands to reason that the final ZnO is no longer a powder, but mostly a big solid lump, which is much less shock absorbent. But don't take my word for it, you could actually open a fresh and a dry alkaline battery and investigate the consistency of the materials.
Don't mind you word, but how on earth you're going to restore the electrons charge and reverse the reaction WHIT A BUMP???
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#34 Reply
Posted by
nitro2k01
on 16 Aug, 2013 09:51
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That's not what I said! Consider the possibility that there's unused zinc powder near the center conductor, or MnO2 near the outer shell, ie in either case far away from the separator so the reaction can't happen optimally. Shake it around and magic happens. But like I said, this effect would be somewhere between non-existent and negligible. The whole point of the electrolyte is to provide good ion flow across the whole battery. But if the electrolyte was somehow dried up, it could theoretically have a small effect.
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#35 Reply
Posted by
ddavidebor
on 16 Aug, 2013 10:24
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Ahhhhhn ok
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#36 Reply
Posted by
Oracle
on 18 Aug, 2013 11:30
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I'm just wondering if this method can be used only whit alkaline batteries or also whit lead acid ones.
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#37 Reply
Posted by
jancumps
on 18 Aug, 2013 12:01
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fail
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#38 Reply
Posted by
555applelc
on 18 Aug, 2013 13:52
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i can't see the video???
because of i come from china???
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#39 Reply
Posted by
dr.diesel
on 18 Aug, 2013 14:02
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i can't see the video???
because of i come from china???
Isn't youtube blocked in China?
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#40 Reply
Posted by
kyndal
on 19 Aug, 2013 08:14
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Before the video you bounced the batteries and then you discharged the two who bounces better. Then you marked them black and made the video.
No need to fake the video. You sorted the batteries before.
I assume you are kidding, right?
no.... this thing stinks to hell and high water like your NE555 discoveries. etc..
fool me.. twice? i lost count.. anyway there is no trust left in this world...... ;o)
saving grace is that its nowhere near april. so i have been bouncing batteries..
that being said.. your probably going to need to build that rig..
weigh some batteries. poke a few holes ?
haha..
mythbusting monday?
/Kyndal
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#41 Reply
Posted by
hammy
on 19 Aug, 2013 09:06
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Before the video you bounced the batteries and then you discharged the two who bounces better. Then you marked them black and made the video.
No need to fake the video. You sorted the batteries before.
I assume you are kidding, right?
Yes, I'm pulling your leg.
I watched the video, I don't believe it. But I also
don't think you fooled us. It's time to buy some batteries ...
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#42 Reply
Posted by
robrenz
on 19 Aug, 2013 11:00
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Here is my GUESS. There is an anode rod that is connected to the negative cap of the battery that runs up through the anode powder. With full charge it is more intimately connected to the anode powder and the anode powder is more rigid itself. A force on the negative cap will try to push the anode rod further into the anode powder causing shear forces at the cylindrical interface of the anode rod and the anode powder and compression forces at the tip of the anode rod. This will make the negative cap more rigid than if there where no anode rod or if the anode rod could move freely (no friction)in the anode powder. So we have a diaphragm spring (negative cap) with a central post (anode rod) that acts as a frictional damper whose damping rate is affected by the mechanical changes in the anode powder caused by the chemical reactions that occur in discharging the battery. Therefore change in the bounce height.
EDIT: The reason the test works somewhat better on a compliant (rubbery) surface is the edge of the negative cap is fairly rigid from its shape and a flat hard surface cannot deflect the diaphragm center into the battery if the diaphragm is flat to begin with. The compliant surface also lessens the need for the battery to be perfectly vertical at impact to get deflection of the diaphragm.
Remember this is all speculation on my part.
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#43 Reply
Posted by
IanB
on 19 Aug, 2013 14:45
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When alkaline batteries discharge the chemical reaction produces bubbles of gas (hydrogen) inside. The gas increases the internal pressure of the cell, blowing it up a bit like a bicycle tire. This gas pressure is also what forces liquid out through the seals when batteries leak.
There are chemicals in the cell designed to absorb the gas and turn it into water, but some gas bubbles are always going to remain, especially if the cell is fully discharged.
So the strongest possibility is that "bouncy cell" = "gassy cell".
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#44 Reply
Posted by
robrenz
on 19 Aug, 2013 15:35
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So we can determine that by drilling a small hole in the edge of a depleted cell to relieve the gas pressure and retest. If same bounce as fresh cell then pressure is it. If same bounce as before more mechanical.
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#45 Reply
Posted by
c4757p
on 19 Aug, 2013 15:52
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I'm not sure that would be a conclusive test, though. Before hydrogen production you have n solid mass + 0 gaseous mass. After, you have n - m solid mass + m gaseous mass, and after drilling a hole, you are only back to n - m solid mass and a lower density. Granted, m is very small, but couldn't the density change possibly make a difference?
As far as I'm concerned, the hydrogen production is plausible enough that I'm willing to take that as an explanation even without testing. As long as it's an established fact that hydrogen is a product of battery operation, which AFAIK it is, then pressurization of the canister seems an obvious result.
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#46 Reply
Posted by
robrenz
on 19 Aug, 2013 16:01
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I just vented several dead bouncy cells with a dremel disc on the positive end and no change in bounce. I don't think pressure is the predominant mechanism. I don't have time right now to do more scientific testing but I might do a video later including showing the spring rate of the negative terminal diaphragm on fresh and depleted cells both vented and unvented on the depleted ones.
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#47 Reply
Posted by
KedasProbe
on 19 Aug, 2013 16:50
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#48 Reply
Posted by
KedasProbe
on 19 Aug, 2013 17:02
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I just vented several dead bouncy cells with a dremel disc on the positive end and no change in bounce.
You have to do that on the one that has a bounce.
(like reducing the pressure of the ball that bounces too much)
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#49 Reply
Posted by
robrenz
on 19 Aug, 2013 17:09
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That is exactly what I did. the bouncy cells are the dead cells. There was no change or decrease in bounce when vented.
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#50 Reply
Posted by
ciccio
on 19 Aug, 2013 19:26
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Well, I'm really astonished: tested more than 40 dead or very discharged batteries (all VARTA INDUSTRIAL) against 10 new, charges batteries: it works. Dead cells bumps and fall down, charged cell stand up.
It's time to find the free time to investigate.
Best regards
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#51 Reply
Posted by
Dread
on 20 Aug, 2013 02:51
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Reply 31 and 42 have the right answers.
While I find the bounce test to be impractical I do know of one practical application for a similar kind of testing.
For a long time myself and several other engineers at work noticed that 9V batteries could easily be tested to see how good they are by squeezing the flat side of the battery between our fingers. A fresh fully charged battery feels solid but a dead battery feels squishy, we could actually see the sides squeeze inward between our fingers. One day we decided to cut one open and what we found was that the material inside had contracted away from the sides as it dried out leaving about .5mm of space going around the battery. It would stand to reason that the same thing happens with the AA battery and the contracted material allows the end cap to flex inward and create a greater bounce. It's funny how stuff that a few engineers played around with 20 years ago comes back up again.
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#52 Reply
Posted by
rsjsouza
on 21 Aug, 2013 18:17
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Why would anyone think this is about weight? Weight changes would not change the bounce.
+1. Although there is a small change in mass given the decrease in energy (nice explanation
here).
A fresh fully charged battery feels solid but a dead battery feels squishy, we could actually see the sides squeeze inward between our fingers.
I wonder if this is still valid if the 9V battery is comprised of six LR61 cells (or AAAA)... (
wikipedia reference)
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#53 Reply
Posted by
PA4TIM
on 26 Aug, 2013 13:33
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Funny, I'm gonna try this.
But about a tear ago I did some testing on batteries. Nicad, nimh, lead batteries and normal akaline. I found out full batteries have an impedance that is Real Ohms with a small inductive imaginair part. Empty but still good rechargable batteries have a higher (AC, 1 kHz ) Rs as full ones but still an imaginairy part close to pure Ohms. A bad battery however has a much bigger negative imaginair impedance part. It is capacitive. I tested this with a lot cells and the measurement is done with a GR1650 and a HP decade to zero the bridge. And checked measurement (not from all tested cells because it takes a lot of time) with a VNA
I made a page about it on my site. The reason I did this test was because I was experimenting with a desulfator. That test is not done yet. The dead battery is still connected to a loader and desulfator (so over a year) and I plan to do some tests again on it if I find the time.
http://www.pa4tim.nl/?p=3550
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yes but would the gas not be within pockets? i'm not sure if the gas would be distributed around the inside of the battery case ready to be released by drilling a hole.
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#58 Reply
Posted by
ornea
on 21 Aug, 2015 12:05
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OMG it is not rocket science...
Charged batteries have more electrons=> more weight,
Empty battery=>less electrons=>less weight.
You can also spin batteries to check if they are charged:
If it is full with electrons, then the battery will not wobble, since the mass is distributed equally through he whole? battery.
In case it is discharged, then it will wobble, because the electrons will shift the mass center...
I dont think electrons are lost. The same net electrons flowing out the neg (pos) equal the net electrons flowing into the pos(neg). The battery does work to push them around.
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#59 Reply
Posted by
eilize
on 23 Aug, 2015 07:37
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Charged batteries have more electrons=> more weight,
Empty battery=>less electrons=>less weight.
You can also spin batteries to check if they are charged:
If it is full with electrons, then the battery will not wobble, since the mass is distributed equally through he whole? battery.
In case it is discharged, then it will wobble, because the electrons will shift the mass center...
nice try ^^
a corpse in free fall gain a speed
that speed....don't depend of the weight
it depend of gravity (ok it change from heigh...you need a lot of difference to see something :p)
a cannonball and a feather fall at the same speed in vacuum
so, it depend of air resistance (no luck a empty and a full battery have the same form or there is not enough difference)
IF you see difference when you let fall 2 battery ,it's because you don't blet fall at the same moment or the don't let fall from the same angle
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#60 Reply
Posted by
tree
on 28 Aug, 2015 23:48
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Question is...If I slip on the batteriser, will the battery bounce higher or lower?
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#61 Reply
Posted by
amyk
on 29 Aug, 2015 15:00
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Question is...If I slip on the batteriser, will the battery bounce higher or lower?
Probably not at all, thus it can increase the charge in the battery and make it last longer.
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#62 Reply
Posted by
Godzil
on 01 Sep, 2015 22:29
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Question is...If I slip on the batteriser, will the battery bounce higher or lower?
Don't do that! With the 800x more energy in your battery you may create a blackhole! That's what batteriser is, accumulating more energy in a small area, like a blackhole does!
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#63 Reply
Posted by
Barny
on 02 Sep, 2015 07:48
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Funfact:
If you try the bounce-test with a button cell, the bouncing effect is extreme.
If you use a small button cell out of an hearing aid, it bounce nearly to the same high if it hit a hard surface when its emty.
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#64 Reply
Posted by
ez24
on 10 Sep, 2015 20:20
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Found this article on the bouncing batteries
http://www.princeton.edu/main/news/archive/S42/72/95S25/index.xml?section=topstories
turns out none of us got it right; @robrenz was the only one on the right track.
Who would have guessed that bouncing batteries gets to this level:
Support for the project was provided in part by the National Science Foundation, the U.S. Department of Energy and Brookhaven National Laboratory.
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#65 Reply
Posted by
apis
on 10 Sep, 2015 22:29
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Nice picture:
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Thanks ez24 for that link, very interesting!
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#67 Reply
Posted by
ez24
on 11 Sep, 2015 19:52
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Thanks ez24 for that link, very interesting!
Thanks but it was not my link -- it came from EvilGeniusSkis
So I also say thanks to EvilGeniusSkis
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ooops, right, thank you both!
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Thanks ez24 for that link, very interesting!
Thanks but it was not my link -- it came from EvilGeniusSkis
So I also say thanks to EvilGeniusSkis
Your welcome
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#70 Reply
Posted by
BrianHG
on 02 Dec, 2018 01:20
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Here is a really good side-by-side comparison of full and empty batteries, and why they bounce higher when they are empty: