EEVblog #865 - How To Increase Alkaline Battery Capacity

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Dave shows you an interesting ionic resistance phenomenon that lets you increase the battery capacity in typical Alkaline AA and AAA cells.

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Very interesting video!
This is a well-known occurrence in batteries with solid particles.

Alkaline batteries (and a great many other batteries) are made with electrodes consisting of powdered zinc for one and powdered carbon and manganese dioxide for the other. Now ideally when you pack them into the battery all the particles in the same electrode will touch and eventually give you a conducting path from every particle to their respective current collector component, a carbon rod or a metal can. BUT, in practice some of the particles will remain suspended in the electrolyte and not conduct. These orphan particles can't be oxidized/reduced in the electrochemical reactions and thus essentially remain unused. Additionally, during discharge, loosely connected structures of particles will disconnect as the weakest particles get oxidized/reduced first and no longer conduct the current of its neighboring particles. So more orphan particles are created. Eventually all the connected particles are discharged and the battery is dead. But these orphan particles remain.

Compressing, striking, grinding, or even sonicating the battery will dislodge the orphan particles and cause them to connect, forming a low-current path to their respective current collectors and giving some extra capacity. This capacity was always in the battery, it was just unavailable. Continued mechanical action will eventually dislodge all available particles and the battery will truly be dead.

This effect is an active area of battery research as it has implications for the life cycles of rechargeable batteries. When a battery is discharged and recharged the particles don't quite recrystallize exactly the same way as in the previous cycle and this leads to increased ESR, physical wear of the membranes and components and other problems that contribute to limited numbers of charge/discharge cycles.

Ways to reduce the effect include better manufacturing methods, additives that make the particles stick together better and prevent the weakest particles from disconnecting, as well as advanced charging/discharge circuitry that presents a pulsating load of a special waveform to the battery that discharges the particles more evenly rather than going after the weakest ones first.

Batteries with molten electrodes, fuel cells, all-liquid electrodes and similar chemistries don't exhibit this particular effect.

NurdRage

I reckon you could get double the capacity if you throw the now squeezed battery into a turbo encabulator for a few minutes but I haven't got one on hand so I can't test.

MrTmelord

When I read " interesting ionic resistance phenomenon " I checked the date and thought you wont fool me! But this is something I used to do years ago when batteries were less plentiful and more expensive. New batteries would be used in a high current draw torch. When the torch got dim they would be transferred to a transistor headphone radio for another few hours of use. When this failed the batteries would be removed and squeezed "laterally" and put back in the radio for another 20 minutes of listening. The other trick that we used to do was put the batteries on a radiator or by the fire to heat them up. Once they were toastie you could get a bit more juice out of them. Definitely worked in the good aul days. SO now I don't know if this is an double bluff type of Aprils fool or not, especially since the other "New Office" video seemed a more obvious type of foolery!

TL:DR This video I believe, The new office one I call Shens!

oOMonkeyMagicOo

Yeah we used to do it back in 1880's, when we had no power in my small village in Morocco to power on the stereo. I used to hammer the top of the batteries like you did here Dave, some other people hammer the battery in all sides, some other people even boil them in water for few Brings back memories

bassalh

It seems natural that when you squeeze the plates together harder, more juice will come out.

Landrew

"I have no idea how much to squeeze it by." Yeah, that's what she said.

Sorry... I'll get my coat.

Thesignalpath

Batterizer better not see this video, they'll kickstart a battery squisher.

Mickice

every kid from the 80/90's with a tv remote knows this squeeze trick, cept you do it on the sides instead of each end, and usually with your teeth lol

Revoku

Didn't work with a car battery. After several hours of jumping up and down on it, all I have is battery acid all over the garage floor.

DaveCurran

so AVE was right all along? keeping something in the vice makes it better?

dukenukem

It would be interesting to put isolated metal plates in the vise with the 4 terminal measurement and give it a squeeze during the discharge to see how much you can spike the output.

stonent

Fuck's sake Dave, did you have to release this on April 1st? Now everybody thinks it's a bloody April fool's joke.

hellterminator

I've heard of similar results from baking the batteries in the oven for a while. People have been known to "recharge" non-rechargeable cells thinking that they are adding power to the battery but all they are really doing is heating up the cell due to the internal resistance.

My guess is that since the cathode of an alkaline electrochemical cell is a solid (manganese dioxide mixed with a liquid electrolyte), the products that result from the chemical reaction that occurs during discharge will stay in place after they form resulting in an area of higher resistance. Squeezing or heating the cell causes these products to become agitated (or perhaps even dissolved in the case of heating), moving them out of the way, effectively eliminating or reducing that area of high resistance and allowing current to flow more easily.

Edit: This most likely occurs on both the inner surface of the battery can (at the cathode) _and_ at the rod going up the middle of the battery (at the anode) where it exchanges ions with a zinc-containing paste or gel. The products that form are manganese(III) oxide (Mn2O3) at the cathode and zinc oxide (ZnO) at the anode. These grow inward as needle-like structures from the outer can into the manganese dioxide/potassium hydroxide mixture at the cathode and outwards from the center rod into the zinc metal/potassium hydroxide solution at the anode. Mn2O3 and ZnO are both non-conducting and basically these two will products build up until the point where they are blocking so much of the surface of the conductors that electrons can no longer get through to initiate the reactions with the manganese dioxide and zinc metal. The needle-like structures are very brittle and fragile so a little bit movement from the squeeze will cause them to break off from the surface of the conductors and migrate into the slurry around them, allowing electron flow to resume and further chemical reactions to take place.

Hope that makes sense.

goyabee

Very interesting. I'd suggest also trying some sideways pressure to see if that also happens

asusreviews

When i was desperate to get more music out of my Walkman/Discman, i used to bite the batteries and/or bash them on the hard metal bits of the train. I didn't know this wasn't common knowledge.

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