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Author Topic: EEVblog #508 - Can You Test Battery Charge By Dropping It?  (Read 9479 times)

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Offline EEVblog

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EEVblog #508 - Can You Test Battery Charge By Dropping It?
« on: August 15, 2013, 07:15:55 PM »
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


Offline ddavidebor

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EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #1 on: August 15, 2013, 07:36:59 PM »
Mmh morning video niceeee

Online adam1213

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #2 on: August 15, 2013, 08:47:15 PM »
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.
« Last Edit: August 15, 2013, 08:50:36 PM by adam1213 »

Citizen

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #3 on: August 15, 2013, 08:56:06 PM »
OMG it is not  rocket science...
 |O

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...

Offline mikeselectricstuff

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #4 on: August 15, 2013, 09:01:14 PM »
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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Offline EEVblog

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #5 on: August 15, 2013, 09:03:52 PM »
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.
« Last Edit: August 15, 2013, 09:12:12 PM by EEVblog »

Offline dr.diesel

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #6 on: August 15, 2013, 09:05:53 PM »
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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Offline EEVblog

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #7 on: August 15, 2013, 09:08:53 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.

Offline tinhead

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #8 on: August 15, 2013, 09:14:05 PM »
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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Offline EEVblog

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #9 on: August 15, 2013, 09:16:27 PM »
  • 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.

Quote
  • 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.

Quote
  • Show that a given battery normally bounces in a certain way.

I can confirm fully charged batteries bounce to roughly the same height.

Citizen

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #10 on: August 15, 2013, 09:17:55 PM »
Lol. i was joking:))
BTW a charged battery has as much electrons in it as a discharged one;)

Offline EEVblog

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #11 on: August 15, 2013, 09:24:09 PM »
KipKay's video is a complete ripoff of this one done a month ago:



Offline Wytnucls

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #12 on: August 15, 2013, 09:32:16 PM »
You could also carefully recharge the depleted battery and see if it stops bouncing.

Offline Psi

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #13 on: August 15, 2013, 09:56:30 PM »
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.
« Last Edit: August 15, 2013, 09:58:46 PM by Psi »
Greek letter 'Psi' (not Pounds per Square Inch)

Offline ddavidebor

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EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #14 on: August 15, 2013, 11:05:01 PM »
No

Offline Wytnucls

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #15 on: August 16, 2013, 12:00:58 AM »
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.

Offline lewis

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #16 on: August 16, 2013, 01:35:04 AM »
Is it April 1st already?
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Offline LaurenceW

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #17 on: August 16, 2013, 02:29:45 AM »
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.
If you don't measure, you don't get.

Offline KedasProbe

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #18 on: August 16, 2013, 04:25:33 AM »
Maybe you can drill into one at the top to let the gas out.
Not everything that counts can be measured. Not everything that can be measured counts.
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Offline hammy

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #19 on: August 16, 2013, 06:36:47 AM »
... 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.  :=\

Offline Legit-Design

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #20 on: August 16, 2013, 06:39:01 AM »
... 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.
« Last Edit: August 16, 2013, 06:40:59 AM by Legit-Design »

Online IanB

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #21 on: August 16, 2013, 06:51:14 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.
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Offline firewalker

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #22 on: August 16, 2013, 07:46:49 AM »
Take two metal cylinders. Fill them with water. Freeze the one. Drop them.

Alexander.
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Offline Psi

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #23 on: August 16, 2013, 08:06:57 AM »
No
You can't say that unless you've actually tested it.
« Last Edit: August 16, 2013, 08:08:35 AM by Psi »
Greek letter 'Psi' (not Pounds per Square Inch)

Offline EEVblog

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Re: EEVblog #508 - Can You Test Battery Charge By Dropping It?
« Reply #24 on: August 16, 2013, 09:14:09 AM »
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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