Author Topic: EEVblog #508 - Can You Test Battery Charge By Dropping It?  (Read 21789 times)

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Offline Excavatoree

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #25 on: August 16, 2013, 09:19:37 am »
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?
 

Offline PeteInTexas

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #26 on: August 16, 2013, 03:54:08 pm »
Gives a whole new meaning to "dead cat bounce"



« Last Edit: August 16, 2013, 04:09:41 pm by PeteInTexas »
 

Offline PeteInTexas

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #27 on: August 16, 2013, 04:17:37 pm »
OMG it is not  rocket science...
 |O
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.

No, no you're both wrong.  Its the Earth's magnetic  field: no charge, no attraction to either pole to drag the bounce hence a higher bounce.  Full charge, greater attraction to opposite pole to drag the bounce hence a thud. >:D ;D
« Last Edit: August 16, 2013, 04:19:51 pm by PeteInTexas »
 

Offline IanB

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #28 on: August 16, 2013, 04:46:25 pm »
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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Offline 99tito99

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #29 on: August 16, 2013, 05:05:49 pm »
Poke a hole in the discharged bat to relieve the pressure, then check the bounce.
Cheers, Mark
 

Offline ddavidebor

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EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #30 on: August 16, 2013, 06:57:26 pm »
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.
Davide Bortolami,
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Offline nitro2k01

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #31 on: August 16, 2013, 07:36:11 pm »
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.
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Offline nitro2k01

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #32 on: August 16, 2013, 07:42:24 pm »
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.
Whoa! How the hell did Dave know that Bob is my uncle? Amazing!
 

Offline ddavidebor

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EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #33 on: August 16, 2013, 07:44:03 pm »
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???
Davide Bortolami,
Fermium LABS srl
 

Offline nitro2k01

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #34 on: August 16, 2013, 07:51:30 pm »
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.
Whoa! How the hell did Dave know that Bob is my uncle? Amazing!
 

Offline ddavidebor

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EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #35 on: August 16, 2013, 08:24:50 pm »
Ahhhhhn ok
Davide Bortolami,
Fermium LABS srl
 

Oracle

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #36 on: August 18, 2013, 09:30:52 pm »
I'm just wondering if this method can be used only whit alkaline batteries or also whit lead acid ones.
 

Offline jancumps

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #37 on: August 18, 2013, 10:01:04 pm »
fail

 

Offline 555applelc

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #38 on: August 18, 2013, 11:52:26 pm »
i can't see the video???
because of i come from china???
 

Offline dr.diesel

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #39 on: August 19, 2013, 12:02:18 am »
i can't see the video???
because of i come from china???

Isn't youtube blocked in China?

Offline kyndal

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #40 on: August 19, 2013, 06:14:04 pm »
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

 
 

Offline hammy

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #41 on: August 19, 2013, 07:06:31 pm »
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.  >:D

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 ...  :-DMM
« Last Edit: August 20, 2013, 05:03:42 am by hammy »
 

Offline robrenz

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #42 on: August 19, 2013, 09:00:51 pm »
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.
« Last Edit: August 19, 2013, 09:12:31 pm by robrenz »
 

Offline IanB

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #43 on: August 20, 2013, 12:45:31 am »
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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Offline robrenz

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #44 on: August 20, 2013, 01:35:46 am »
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.
« Last Edit: August 20, 2013, 01:56:50 am by robrenz »
 

Offline c4757p

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #45 on: August 20, 2013, 01:52:45 am »
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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Offline robrenz

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #46 on: August 20, 2013, 02:01:40 am »
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.

Offline KedasProbe

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #47 on: August 20, 2013, 02:50:17 am »
in a Nickel-Cadmium battery you have a different pressure curve:
http://batteryuniversity.com/learn/article/charging_nickel_based_batteries
(should act the other way around)
Not everything that counts can be measured. Not everything that can be measured counts.
[W. Bruce Cameron]
 

Offline KedasProbe

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #48 on: August 20, 2013, 03:02:17 am »
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)
Not everything that counts can be measured. Not everything that can be measured counts.
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Offline robrenz

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #49 on: August 20, 2013, 03:09:43 am »
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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