# Can you actually charge a battery by rubbing it on something?



## Minjin (Nov 12, 2009)

Just as it says in the title, can you charge/recharge any kind of consumer battery by rubbing it on your pants/shirt/whatever? This is one of those tricks that I heard a long time ago. I've tried it and it has seemed to work. I've even told many other people to do it. Now that I'm a little older and wiser, I'm beginning to think that it's bunk. I think that when you pull the batteries out of a circuit, you're simply giving them a chance to relax and recover a little bit of charge. I'm going to do an experiment to prove if it works but I thought I'd see what you guys have to say first. Thoughts for or against? I'm completely open to anything.

If you think it works, can you tell me a mechanism how it would work? Also, any particular techniques I should try? Such as a finger on each terminal, rubbing in a certain direction, on a certain surface, etc.

Thanks for any help. :wave:


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## Mr Happy (Nov 12, 2009)

Rubbing a battery is likely to warm it up a touch, which will "liven it up" just a tiny bit. Clasping it in your hand would do just as well.

This is not going to recharge it though, it will just give another minute or two of life out of it.


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## 45/70 (Nov 12, 2009)

Mr Happy said:


> Rubbing a battery is likely to warm it up a touch, which will "liven it up" just a tiny bit. Clasping it in your hand would do just as well.
> 
> This is not going to recharge it though, it will just give another minute or two of life out of it.




Damn! All these years, I'm going to have to try that! 

Dave


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## TorchBoy (Nov 12, 2009)

When I was really young the story was that placing a battery on a heater would recharge it. Invoking static electricity sounds much more fun.


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## lctorana (Nov 12, 2009)

Minjin said:


> I think that when you pull the batteries out of a circuit, you're simply giving them a chance to relax and recover a little bit of charge.


This effect, while genuine, is not terribly pronounced, except in the case of plain Zinc-Carbon cells, particularly large ones.

Which rules out almost everything we use in flashlights these days.


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## 45/70 (Nov 13, 2009)

In all seriousness, what this really does is improve the conductivity of the contact area. Nickel, which most battery cell contacts are (or more than likely, are plated with), while an OK conductor, tarnishes after time. Rubbing the surfaces on cloth removes the tarnish and promotes better contact.

I don't buy the heating effect as much as the improvement in contact. It might help a bit though if, as Mr Happy said, you hold it in your hand a few minutes.

Dave


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## biggerdog (Nov 13, 2009)

45/70 said:


> In all seriousness, what this really does is improve the conductivity of the contact area. Nickel, which most battery cell contacts are (or more than likely, are plated with), while an OK conductor, tarnishes after time. Rubbing the surfaces on cloth removes the tarnish and promotes better contact.
> 
> Dave


 
Absolutely true. Furthermore, the improvement is generally much more noticeable when the cell is nearly depleted, simply because the the loss, coupled with low cell voltage, pushes things over the edge for many devices.


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## MorePower (Nov 13, 2009)

45/70 said:


> In all seriousness, what this really does is improve the conductivity of the contact area. Nickel, which most battery cell contacts are (or more than likely, are plated with), while an OK conductor, tarnishes after time. Rubbing the surfaces on cloth removes the tarnish and promotes better contact.
> 
> I don't buy the heating effect as much as the improvement in contact. It might help a bit though if, as Mr Happy said, you hold it in your hand a few minutes.
> 
> Dave



I'd have to disagree on this one. An increase of just 1 or 2 degrees is enough to noticeably improve discharge characteristics of a cell. A minor increase of conductivity (which is already quite good) at the contact area is unlikely to give even an additional minute or two of runtime.

When a cell is almost completely discharged, a slight increase in temperature can increase the electrochemical activity of any remaining anode and cathode material, as well as improve electrolyte dispersion within the cell. These effects will far outweigh contact conductivity increase.


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## Zeruel (Nov 13, 2009)

TorchBoy said:


> When I was really young the story was that placing a battery on a heater would recharge it. Invoking static electricity sounds much more fun.



For me is putting them in the sunlight. :laughing:


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## 45/70 (Nov 13, 2009)

MorePower said:


> I'd have to disagree on this one.




Fine! Be that way! Far be it from me to argue with a "Master". 

I didn't say that the heat factor wouldn't have a positive effect. I'll stick to my guns though. When the nipple and tail of a cell are tarnished enough that they are darkened, as with a device that is stored more than used, the connection factor is more important IMO.

From personal experience, when the contacts are cleaned in this manner, the device can continue to work better for days. This would rule out cell heating being a factor.

Dave


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## hopkins (Nov 13, 2009)

2 different types of metal in contact, with electricity
flowing through that contact. (in air)

Would not some resistive products be created over the discharge life
of the battery?

Or is it standard engineering practice that every contact inside battery holders
be made from the same exact metal as battery ends are?


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## Turbo DV8 (Nov 14, 2009)

MorePower said:


> I'd have to disagree on this one. A minor increase of conductivity at the contact area is unlikely to give even an additional minute or two of runtime.


 
It depends on the device. I have a digital camera which sits in the trunk of the car for months of non-use with lithium cells in it. The camera is seldom used, and the lithiums are basically new. Sometimes when I go to use the camera, it won't power up, or it will power up then quickly shut down, indicating low battery power. If I remove the cells and wipe the contacts, the camera powers up fine, indicating full battery power. I also believe in this case the "tarnishing" does not even have to be grossly visible to cause poor enough contact to make the camera believe the cells are dead. So, in some case, even minor changes in conductivity can have a large consequence.

I also have a battery operated fan that uses NiMH D cells. The positive contact plating of the batteries and fan have dulled due to vibration in my backpack during motorcycle transport. I have to regularly wipe the contacts clean, or else the fan runs erratically and/or slowly. It took a while to figure it was the battery contacts. I figured it was the brushes or switch, or some other cheap component that would cause it to run erratically shortly after I changed the batteries. Then I wiped the batteries and fan contact and it was like new. Now I stuff a small piece of folded up aluminum foil between the positive fan contact to increase the contact area. Problem solved.

So, cleaning even minor oxidation can very well yield significantly better run time and performance.


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## Mr Happy (Nov 14, 2009)

If the two electrical contacts are different metals and there is any moisture around you can get galvanic corrosion. Thin films of oxidation can have significant resistance. The extreme case of this is anodizing -- see how the metal body of an aluminum flashlight is a perfect insulator in spite of its bright metallic appearance.

Contact resistance is easily seen in cheap flashlights. Have you noticed how a light will tend to be dim and flickery if you take it out of a drawer after a period of storage? But rotate the batteries against the contacts and it will go nice and bright again.


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## yellow (Nov 14, 2009)

id say its heating up the cell.
Normally lights are used at night, when for most parts of the year it is "cold".
Maybe cold enough that "heating" the battery gives some effect.

The colder the temp, the more noticeable
(expecially with those old incan lights which also improved from lesser internal resistance, a modern led driver might not have such a dramatic effect)


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## TorchBoy (Nov 14, 2009)

Turbo DV8 said:


> So, cleaning even minor oxidation can very well yield significantly better run time and performance.


If it was resistance causing the poor performance wouldn't that extend the runtime? (Poor as the performance during that runtime may be.)


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## bhds (Nov 14, 2009)

As the other posters have stated, rubbing the contacts does clean up the corrosion and improves conductivity. I have been doing this for years with my tv and vcr remotes. In fact, a lot of the times if my remote stops working, I will simply open the cover and just rotate the batteries in place without removing them. This gives the contacs a nice clean electrical path. The remote will "magically" start working, for quite a while I might add. :thumbsup:


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## Turbo DV8 (Nov 14, 2009)

TorchBoy said:


> If it was resistance causing the poor performance wouldn't that extend the runtime? (Poor as the performance during that runtime may be.)


 
I hear where you're coming from on that. My (perhaps misleading) use of the term "runtime" refers to useable runtimes in the two examples I noted. Before cleaning, the useable runtimes in the examples were next to nothing, since they barely worked.


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## Minjin (Nov 14, 2009)

bhds said:


> As the other posters have stated, rubbing the contacts does clean up the corrosion and improves conductivity. I have been doing this for years with my tv and vcr remotes. In fact, a lot of the times if my remote stops working, I will simply open the cover and just rotate the batteries in place without removing them. This gives the contacs a nice clean electrical path. The remote will "magically" start working, for quite a while I might add. :thumbsup:


I do the same as well. In older Volvos with cylindrical pointed fuses, just running a finger down the fusebox, spinning each one, will often times fix electrical problems. 

So no one actually thinks it's a static electricity thing? I should be able to test the heat thing pretty easily with my box of nearly dead batteries. The contact issue seems a little more difficult to test since it is so dependent on what and how you're touching the pads.


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## TorchBoy (Nov 14, 2009)

Minjin said:


> So no one actually thinks it's a static electricity thing?


I was just joking when I mentioned it in my earlier post. (Just in case that wasn't clear.)


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## Minjin (Nov 14, 2009)

TorchBoy said:


> I was just joking when I mentioned it in my earlier post. (Just in case that wasn't clear.)


Oh, I'm not referring to you at all. I've talked to some people who think that is what is actually happening...


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## shadowjk (Nov 15, 2009)

An old teacher of mine in highschool said when he was young he used to put the batteries on the oven to get a few more minutes out of the flashlight.

I imagine it worked better with old heavy duty type carbon cells.


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## Turbo DV8 (Nov 15, 2009)

Minjin said:


> So no one actually thinks it's a static electricity thing?


 
Even if one were talented enough to be able to divine the static electricity to the charge goes to the appropriate pole (!) I would imagine it would require a whole lot of rubbing! You'd have to put the cell in your pant pocket and rub all day to get any appreciable charge, but you might be hauled off to jail under presumption of lewd and lascivious conduct.


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## Radiophile (Nov 15, 2009)

Are you rubbing the battery across the terminals of a charger?


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