EEVblog #508 - Can You Test Battery Charge By Dropping It? - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: August 15, 2013, 09:15:55 am
content: 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

author: ddavidebor
author_rank: Super Contributor
timestamp: August 15, 2013, 09:36:59 am
content: Mmh morning video niceeee

author: adam1213
author_rank: Regular Contributor
timestamp: August 15, 2013, 10:47:15 am
content: 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 videoShow that a given battery normally bounces in a certain way.

author: Unknown
author_rank: Unknown
timestamp: August 15, 2013, 10:56:06 am
content: 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...

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 15, 2013, 11:01:14 am
content: 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

author: EEVblog
author_rank: Unknown
timestamp: August 15, 2013, 11:03:52 am
content: Quote from: adam1213 on August 15, 2013, 10:47:15 amI 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.

author: dr.diesel
author_rank: Super Contributor
timestamp: August 15, 2013, 11:05:53 am
content: Quote from: mikeselectricstuff on August 15, 2013, 11:01:14 amPerhaps some of the same reason dead batteries are prone to leaking as well.

author: EEVblog
author_rank: Unknown
timestamp: August 15, 2013, 11:08:53 am
content: Quote from: Citizen on August 15, 2013, 10:56:06 amTo 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.

author: tinhead
author_rank: Super Contributor
timestamp: August 15, 2013, 11:14:05 am
content: Quote from: mikeselectricstuff on August 15, 2013, 11:01:14 amright, 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.

author: EEVblog
author_rank: Unknown
timestamp: August 15, 2013, 11:16:27 am
content: Quote from: adam1213 on August 15, 2013, 10:47:15 amUsing a multimeter to determine a batteries charge level is a very poor way to do it.QuoteI will do that, but I need some bits and more time.QuoteI can confirm fully charged batteries bounce to roughly the same height.

author: Unknown
author_rank: Unknown
timestamp: August 15, 2013, 11:17:55 am
content: Lol. i was joking:))BTW a charged battery has as much electrons in it as a discharged one;)

author: EEVblog
author_rank: Unknown
timestamp: August 15, 2013, 11:24:09 am
content: KipKay's video is a complete ripoff of this one done a month ago:

author: Wytnucls
author_rank: Super Contributor
timestamp: August 15, 2013, 11:32:16 am
content: You could also carefully recharge the depleted battery and see if it stops bouncing.

author: Psi
author_rank: Super Contributor
timestamp: August 15, 2013, 11:56:30 am
content: 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.

author: ddavidebor
author_rank: Super Contributor
timestamp: August 15, 2013, 01:05:01 pm
content: No

author: Wytnucls
author_rank: Super Contributor
timestamp: August 15, 2013, 02:00:58 pm
content: 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.

author: lewis
author_rank: Frequent Contributor
timestamp: August 15, 2013, 03:35:04 pm
content: Is it April 1st already?

author: LaurenceW
author_rank: Frequent Contributor
timestamp: August 15, 2013, 04:29:45 pm
content: 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.

author: KedasProbe
author_rank: Frequent Contributor
timestamp: August 15, 2013, 06:25:33 pm
content: Maybe you can drill into one at the top to let the gas out.

author: hammy
author_rank: Unknown
timestamp: August 15, 2013, 08:36:47 pm
content: Quote from: EEVblog on August 15, 2013, 11:08:53 amBefore 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. Yousortedthe batteries before.

author: Legit-Design
author_rank: Frequent Contributor
timestamp: August 15, 2013, 08:39:01 pm
content: Quote from: hammy on August 15, 2013, 08:36:47 pmFor 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.

author: IanB
author_rank: Super Contributor
timestamp: August 15, 2013, 08:51:14 pm
content: 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.

author: firewalker
author_rank: Super Contributor
timestamp: August 15, 2013, 09:46:49 pm
content: Take two metal cylinders. Fill them with water. Freeze the one. Drop them.Alexander.

author: Psi
author_rank: Super Contributor
timestamp: August 15, 2013, 10:06:57 pm
content: Quote from: ddavidebor on August 15, 2013, 01:05:01 pmYou can't say that unless you've actually tested it.

author: EEVblog
author_rank: Unknown
timestamp: August 15, 2013, 11:14:09 pm
content: Quote from: hammy on August 15, 2013, 08:36:47 pmI assume you are kidding, right?

author: Excavatoree
author_rank: Frequent Contributor
timestamp: August 15, 2013, 11:19:37 pm
content: Quote from: IanB on August 15, 2013, 08:51:14 pmI'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?

author: PeteInTexas
author_rank: Frequent Contributor
timestamp: August 16, 2013, 05:54:08 am
content: Gives a whole new meaning to "dead cat bounce"

author: PeteInTexas
author_rank: Frequent Contributor
timestamp: August 16, 2013, 06:17:37 am
content: Quote from: EEVblog on August 15, 2013, 11:08:53 amNo, 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.

author: IanB
author_rank: Super Contributor
timestamp: August 16, 2013, 06:46:25 am
content: Quote from: Excavatoree on August 15, 2013, 11:19:37 pmSure, 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.

author: 99tito99
author_rank: Regular Contributor
timestamp: August 16, 2013, 07:05:49 am
content: Poke a hole in the discharged bat to relieve the pressure, then check the bounce.Cheers, Mark

author: ddavidebor
author_rank: Super Contributor
timestamp: August 16, 2013, 08:57:26 am
content: Quote from: Psi on August 15, 2013, 10:06:57 pmIf i've understand the question then is no. That kind of things just don't happen.

author: nitro2k01
author_rank: Frequent Contributor
timestamp: August 16, 2013, 09:36:11 am
content: Quote from: ddavidebor on August 16, 2013, 08:57:26 amWhat 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.

author: nitro2k01
author_rank: Frequent Contributor
timestamp: August 16, 2013, 09:42:24 am
content: 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.

author: ddavidebor
author_rank: Super Contributor
timestamp: August 16, 2013, 09:44:03 am
content: Quote from: nitro2k01 on August 16, 2013, 09:36:11 amDon't mind you word, but how on earth you're going to restore the electrons charge and reverse the reaction WHIT A BUMP???

author: nitro2k01
author_rank: Frequent Contributor
timestamp: August 16, 2013, 09:51:30 am
content: That's not what I said! Consider the possibility that there's unused zinc powder near the center conductor, or MnO2near 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.

author: ddavidebor
author_rank: Super Contributor
timestamp: August 16, 2013, 10:24:50 am
content: Ahhhhhn ok

author: Unknown
author_rank: Unknown
timestamp: August 18, 2013, 11:30:52 am
content: I'm just wondering if this method can be used only whit alkaline batteries or also whit lead acid ones.

author: jancumps
author_rank: Unknown
timestamp: August 18, 2013, 12:01:04 pm
content: fail

author: 555applelc
author_rank: Newbie
timestamp: August 18, 2013, 01:52:26 pm
content: i can't see the video???because of i come from china???

author: dr.diesel
author_rank: Super Contributor
timestamp: August 18, 2013, 02:02:18 pm
content: Quote from: 555applelc on August 18, 2013, 01:52:26 pmIsn't youtube blocked in China?

author: kyndal
author_rank: Regular Contributor
timestamp: August 19, 2013, 08:14:04 am
content: Quote from: EEVblog on August 15, 2013, 11:14:09 pmno.... 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

author: hammy
author_rank: Unknown
timestamp: August 19, 2013, 09:06:31 am
content: Quote from: EEVblog on August 15, 2013, 11:14:09 pmYes, I'm pulling your leg.I watched the video, I don't believe it. But I alsodon't thinkyou fooled us. It's time to buy some batteries ...

author: robrenz
author_rank: Super Contributor
timestamp: August 19, 2013, 11:00:51 am
content: Here is myGUESS. 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 allspeculationon my part.

author: IanB
author_rank: Super Contributor
timestamp: August 19, 2013, 02:45:31 pm
content: 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".

author: robrenz
author_rank: Super Contributor
timestamp: August 19, 2013, 03:35:46 pm
content: 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.

author: c4757p
author_rank: Super Contributor
timestamp: August 19, 2013, 03:52:45 pm
content: I'm not sure that would be a conclusive test, though. Before hydrogen production you havensolid mass + 0 gaseous mass. After, you haven - msolid mass +mgaseous mass, and after drilling a hole, you are only back ton - msolid mass and a lower density. Granted,mis 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 hydrogenisa product of battery operation, which AFAIK it is, then pressurization of the canister seems an obvious result.

author: robrenz
author_rank: Super Contributor
timestamp: August 19, 2013, 04:01:40 pm
content: 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.

author: KedasProbe
author_rank: Frequent Contributor
timestamp: August 19, 2013, 04:50:17 pm
content: 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)

author: KedasProbe
author_rank: Frequent Contributor
timestamp: August 19, 2013, 05:02:17 pm
content: Quote from: robrenz on August 19, 2013, 04:01:40 pmYou have to do that on the one that has a bounce.(like reducing the pressure of the ball that bounces too much)

author: robrenz
author_rank: Super Contributor
timestamp: August 19, 2013, 05:09:43 pm
content: That is exactly what I did. the bouncy cellsarethe dead cells. There was no change or decrease in bounce when vented.

author: ciccio
author_rank: Frequent Contributor
timestamp: August 19, 2013, 07:26:49 pm
content: 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

author: Dread
author_rank: Regular Contributor
timestamp: August 20, 2013, 02:51:34 am
content: 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.

author: rsjsouza
author_rank: Super Contributor
timestamp: August 21, 2013, 06:17:18 pm
content: Quote from: mikeselectricstuff on August 15, 2013, 11:01:14 am+1. Although there is a small change in mass given the decrease in energy (nice explanationhere).Quote from: Dread on August 20, 2013, 02:51:34 amI wonder if this is still valid if the 9V battery is comprised of six LR61 cells (or AAAA)... (wikipedia reference)

author: PA4TIM
author_rank: Super Contributor
timestamp: August 26, 2013, 01:33:31 pm
content: 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 VNAI 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

author: dexters_lab
author_rank: Unknown
timestamp: August 26, 2013, 08:40:59 pm
content: 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.

author: EvilGeniusSkis
author_rank: Regular Contributor
timestamp: June 04, 2015, 02:42:54 am
content: Found this article on the bouncing batterieshttp://www.princeton.edu/main/news/archive/S42/72/95S25/index.xml?section=topstoriesturns out none of us got it right; @robrenz was the only one on the right track.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 04, 2015, 06:54:38 pm
content: Quote from: EvilGeniusSkis on June 04, 2015, 02:42:54 amVery interesting article.Thank you very much !

author: EvilGeniusSkis
author_rank: Regular Contributor
timestamp: June 04, 2015, 09:55:21 pm
content: Quote from: HighVoltage on June 04, 2015, 06:54:38 pmYour Welcome, I read the article and the immediately thought of putting it on here for everyone else to read.Maybe Dave should add a link in the video.

author: ornea
author_rank: Unknown
timestamp: August 21, 2015, 12:05:00 pm
content: Quote from: Citizen on August 15, 2013, 10:56:06 amI 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.

author: eilize
author_rank: Contributor
timestamp: August 23, 2015, 07:37:45 am
content: Quotenice try ^^a corpse in free fall gain a speedthat speed....don't depend of the weightit 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 vacuumso, 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

author: tree
author_rank: Regular Contributor
timestamp: August 28, 2015, 11:48:34 pm
content: Question is...If I slip on the batteriser, will the battery bounce higher or lower?

author: amyk
author_rank: Super Contributor
timestamp: August 29, 2015, 03:00:23 pm
content: Quote from: tree on August 28, 2015, 11:48:34 pmProbably not at all, thus it can increase the charge in the battery and make it last longer.

author: Godzil
author_rank: Frequent Contributor
timestamp: September 01, 2015, 10:29:15 pm
content: Quote from: tree on August 28, 2015, 11:48:34 pmDon'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!

author: Barny
author_rank: Frequent Contributor
timestamp: September 02, 2015, 07:48:58 am
content: 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.

author: ez24
author_rank: Super Contributor
timestamp: September 10, 2015, 08:20:14 pm
content: Quote from: EvilGeniusSkis on June 04, 2015, 02:42:54 amWho 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.

author: apis
author_rank: Super Contributor
timestamp: September 10, 2015, 10:29:14 pm
content: Nice picture:

author: vinicius.jlantunes
author_rank: Regular Contributor
timestamp: September 11, 2015, 01:20:55 pm
content: Thanks ez24 for that link, very interesting!

author: ez24
author_rank: Super Contributor
timestamp: September 11, 2015, 07:52:17 pm
content: Quote from: vinicius.jlantunes on September 11, 2015, 01:20:55 pmThanks but it was not my link -- it came from EvilGeniusSkisSo I also say thanks to EvilGeniusSkis

author: vinicius.jlantunes
author_rank: Regular Contributor
timestamp: September 11, 2015, 08:08:06 pm
content: ooops, right, thank you both!

author: EvilGeniusSkis
author_rank: Regular Contributor
timestamp: September 28, 2015, 03:24:10 am
content: Quote from: ez24 on September 11, 2015, 07:52:17 pmYour welcome

author: BrianHG
author_rank: Super Contributor
timestamp: December 02, 2018, 01:20:13 am
content: Here is a really good side-by-side comparison of full and empty batteries, and why they bounce higher when they are empty: