How to Fix Corroded Battery Terminals

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About: I've always liked pulling things apart - it's the putting back together again that I have some issues with.

Many a time I’ve managed to get my hands on some electronic gizmo only to find that the battery compartment totally corroded. It’s usually one of the main reasons I think that people throw toys and whatever else takes batteries away.

The corrosion is caused by potassium hydroxide which can leak out of alkaline batteries (these are the usual types of batteries you put inside toys etc). All batteries discharge, either through use or just slowly through the production of hydrogen gas which forms pressure in the battery. Eventually that pressure will find a way out through a seal or as the battery ages, through corrosion or rust in the outer shell.

As soon as the first signs of a leak forms, then the best thing to do is to get rid of the battery. if you don’t get to it in time however, then the corrosion can grow and spread out of the battery which causes oxidisation and corrosion of the terminals making your device caput.

This Instructable will go through a couple of ways that you can fix your device to bring it back to life again. The first is the most extreme corrosion where the terminals have to be replaced, the second is a small amount of oxidisation which only needed the potassium hydroxide to be neutralised and the terminals to be cleaned.

You can take precautions though to stop this happening such as not mixing different battery types in the same device, replacing all of the batteries at the same time, storing in a dry place and at room temperature, and removing batteries for storage of devices. I’m inherently optimistic (and also lazy) so I’ve never taken any of these precautions but it’s definitely good practice, especially with expensive electronic goods.

Step 1: Parts and Tools

Your parts are going to be any electronic goods that need terminal cleaning and/or relacing. The following though will come in handy when you are going this type of work

Tools

1. Battery Holders. I have a bunch of these lying around which are good for projects. You can also use the terminals from them to repair other electronic goods.

2. You can also just buy these terminals from eBay

2. Small files

3. Vinegar

4. Small paint brush

5. Needle nose pliers

6. Ear cleaners

7. Wire cutters

8. Soldering iron

9. Rubber gloves – to protect your skin from the potassium hydroxide. I have touched it before and it does mildly irritate the skin so it’s best to use gloves when handling.

10. Eye protection – self explanatory

11. Protective mouth and nose mask. Potassium hydroxide can be quite dangerous and breathing it in can be toxic. Better to be safe then sorry.

Step 2: Removing Leaking Batteries

Don’t use your fingers to try and remove the batteries. The potassium hydroxide inside the battery can irritate your skin (I know as I’ve touched it before!). Potassium hydroxide is a caustic agent and is the chemical that corrodes the terminals and destroys the batteries. You may have also seen a feathery crystalline structure forming around the battery and terminal as well. This is potassium carbonate and forms when the potassium hydroxide reacts with carbon dioxide in the air.

For those who want to understand more about the chemical components inside an alkaline battery, please check out the following

Steps:

1. Place a set of rubber gloves on and some safety glasses

2. Use a small screwdriver to pull the batteries out. The glasses here are very important as it is easy to flick small pieces of the corrosion whist pulling out the batteries.

3. Sometimes that batteries can be so corroded that they virtually weld themselves to the terminals. In this case you will need to use a large screwdriver and maybe some pliers to remove them. You’ll probably rip out the terminals as well so be careful you don’t pull any wires out at the same time

4. Dispose of the batteries in a plastic bag.

Step 3: Removing the Corroded Terminals

Next thing to do is to remove all of the corroded terminals. It can be tricky sometimes to do this if they are severely corroded as bits can break off and the grooves in the battery holder can get clogged-up.

Steps:

1. Use a small, thin screwdriver and push this between the top of the terminal and the battery holder. This should bend out the terminal

2. With a pair of needle nosed pliers, grab hold of the terminal and pull it out.

3. If the terminal has solder points, make sure you de-solder or cut the wires and cut them away to be able to remove them easily

4. Dispose of the corroded terminals once removed

Step 4: Cleaning the Battery Cover

The battery holder that I fixed came away from the torch so make it easy to wash and clean. However, this might not always be the case as it will depend on what type of electronics you are cleaning.

Steps:

1. You can neutralise any leftover potassium hydroxide (a caustic agent which acts a little like acid) with some vinegar. Many comments have been made on this in the comments section and initially I also included baking soda as a way to neutralise the alkaline. I've removed this as there is a fair bit of contention if this would actually work or not.

2. Next if possible, wash out the bottom of the battery holder and clean any of the old potassium hydroxide away from the case. If you can’t remove the battery holder, then you are going to have to be a lot more careful when cleaning the area. Use a damp cloth instead of running water and remove any leftover potassium hydroxide residue

3. Next, you may need to remove any pieces of terminal or corrosion that is in-between the grooves that the terminals sit in. Use something thin and sharp to remove anything lodged inside the grooves.

4. Lastly, give the area a clean with some Isopropyl Cleaning Alcohol to remove any last traces of oils, stains etc.

Step 5: Sourcing Some Battery Terminals

In some cases, the corrosion is so bad that you need to replace the terminals inside the battery compartment. One of the easiest places to get these is from old battery holders. You could also grab the terminals out of any old electronic parts.

You can also buy the terminals from eBay and I have put a link in the parts section

Steps:

1 If your battery terminals have tabs on the back, make sure you lift these up first. You might also need to de-solder any wires on them if you got the terminals out of a toy etc.

2 Next, use a small screwdriver to push them out of the battery holder. Just place the tip of the screwdriver into the bottom of the terminal and lift it out of the battery holder. They are held in place by a couple of grooves in the side of the battery holder so should come out relatively easily.

Step 6: Modifying the Battery Terminals

Chances are you will need to modify the battery terminals so they will fit into the batter holder. You can do this pretty easily with some wire cutters and a dremel if you have one.

Steps:

1 First, try and fit one of the terminals into the battery holder grooves. If it does fit, then you can probably ignore this step and move onto the next. If not, then you will need to modify it.

2 Trim the sides of the terminal with some wire cutters and try to push into the grooves again in the battery holder

3 I also had to add a small slit into the terminal in order for them to fit which I did with a dremel.

4 Once you have modified, it’s then time to add them to the battery holder

Step 7: Putting the Battery Terminals in Place

Steps:

1. The first thing to do is to determine the orientation of the terminals. You need to make sure that the spring section on the terminal will be touching the negative part of the battery and the flat section is touching the positive.

2. Usually you can just look on the bottom of the battery holder and there will be images or the orientation. If not, then work out where the positive wire is going to be connected to the terminal and use this as a guide on the orientation of the terminals.

3. Place the terminals into the battery holder grooves and push into place. If they are a little loose then usually the batteries will hold them into place. However, you can slightly bend the terminal and push it back into the grooves which will make the fit a little tighter.

4. Once you have all of the terminals in place, solder the positive and negative wires to the solder points on the terminals

Step 8: Add Some Fresh Batteries and Test

Steps:

1. Before you screw everything back into place, add some batteries and make sure everything works as it should.

2. If everything works ok – replace the screws and covers and whatever else needs replacing to finish off your part

3. Lastly, give it another test and make sure it works

4. Now if you don’t want to have to do this all over again, go back to the intro and follow the precautions

This is really the most extreme case of having to fix battery terminals. The next sample, I think is more common and is more oxidisation of the terminals due to some leakage of the batteries. It’s easier too to fix!

Step 9: Fixing Oxidised and Minor Corroded Terminals

I found this cool, vintage mike at the dump and wanted to try and get it going again. Initially I tested it not knowing that it needed an AA battery and thought it was probably something to do with the wiring. After un-screwing the case however, I discovered that it needed a AA battery to run. The battery had been in place for some time and the terminals were oxidised and had some minor corrosion damage. I could have replaced the terminals but decided it would be easier just cleaning them

Steps:

1. Remove the old battery with a screwdriver and dispose of. Even though there was not as much damage and leakage as the first sample, I still made sure that I wore gloves and eye protection. They are considered safe to dispose of in the bin (imagine how many batteries get thrown away each day!) but there might be some local laws that require you to dispose of them in other ways

2. You can see in the images that there is a little corrosion and potassium hydroxide on the end of the terminal but that the terminal itself looks relatively unaffected structurally.

3. The brown streaks you can see running through the middle of the battery holder is actually glue that has discoloured over time, not corrosion

4. The next step is to neutralise the alkaline from the potassium hydroxide.

Step 10: Neutralise the Acid

Next thing to do is to neutralise any residual potassium hydroxide left of the terminals. There have been many comments left on how best to neutralise the corrosives from the potassium hydroxide. As potassium hydroxide is a strong base, then an acid like vinegar or lemon juice is probably the best thing to use when neutralising an alkaline like potassium hydroxide.

Here's a little more information on acids and bases for those who are interested and how to neutralising.

Steps:

1. First thing to do is to add the vinegar to a small container like a bottle cap lid.

2. Next, add a little to each terminal with a small paint brush or something similar.

3. Wipe off any excess from the terminals and leave to dry

4. Now that the potassium hydroxide has been neutralised, it’s time to clean-up the terminals

Step 11: Cleaning Up the Terminals

You need to remove any oxidisation and corrosion from the terminals. I find that the best thing to use is a small file but you could use sandpaper or an emery board or nail file as well.

Steps:

1. Use a small, fine file on the terminal until the oxidisation and any corrosion is removed. You may not be able to get it all off but sure you get as much as possible.

2. Once you have removed the oxidisation, give the terminals a clean with some isopropyl alcohol. You can also add some non-oxidising grease to help stop any further oxidisation.

3. You can sometimes remove the terminals from the grooves without having to undo any screws or removing any wires. It can make it easier to file if you can do this – just be careful that you don’t break any wires etc.

Step 12: Add a Fresh Battery and Test

Steps:

1. Once the terminals are clean and back into place, you can add a battery/s and test.

2. As before, it’s best to test before you screw everything back into place

That’s it! Hopefully you have managed to bring something back to life again with only a little bit of work.

Do you have any other tips? Let me know in the comments

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126 Discussions

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lonesoulsurfer

9 months ago

Hi All,

Thanks for the comments. I have updated the section in the Instructable on what to use to neutralise the Potassium Hydroxide that can be produced in Alkaline batteries.

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Wellingtonsaam

5 months ago

This is very helpful. I could have avoided wasting a lot of equipments... Not now. I'll never trash gadgets again. Thankx a lot

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ve6cmm

5 months ago

I can't remember who manufactured the TITANIUM E batteries, and where I can still get them. They were fantastic, providing much more power than regular AAs. I could get hundreds of photos with my camera with the Es and maybe 20 with regular alkaline batteries.

The company I worked for at the time had these in Satellite transponders that lasted 3 years before we would replace them. They still had a fair bit of capacity in them.

I think the company pulled them because they were so good. They weren't inexpensive, costing about $5 Canadian each, but they were well worth the price as they lasted much longer than conventional AAs.

2 replies
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RicksterInstructablesve6cmm

Reply 5 months ago

Energizer “Ultimate Lithium” might be what you’re thinking of.
They come in AA and AAA sizes.
They are slightly higher voltage than alkaline cells, but not enough to be a problem in probably 99% of devices.
They are not rechargeable, but they have at least 50% (according to my testing) morecapacity than the best alkalines. They are also significantly lighter in weight.
They also work much better at low temperatures (below 0C) than alkalines.
And finally, they have better performance in high current devices - such as camera flashes, toys etc.

I have never seen one leak.

They are all around better, except they cost significantly more.

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ve6cmmRicksterInstructables

Reply 5 months ago

I have tried these but thay aren't as good as the Titainium E's. From what I understand, they are no longer available;

I do have to say that this instructable and it's comments have been very interesting. Lots of ideas and methods to consider. Thanks to all.

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RicksterInstructables

Tip 5 months ago

The absolute best thing you can do is to buy a small jar of Caig De-Oxit D100.
(https://www.amazon.com/CAIG-Laboratories-D100L-2DB-Electric-Cleaner/dp/B0002BBVN2). Buy the small bottle that comes with an applicator brush in the cap. It’s like a nail polish bottle.
It may seem expensive, but a little goes a long way and it will last you for many years. I discovered it many years ago. I only just recently had to purchase a new bottle.

It prevents corrosion of the terminals. It helps clean corroded ones.
You will never have to “shake” a flashlight again to get it to work.
If your batteries do leak, it’s much easier to clean up the mess.

Any/every time I install or replace batteries I always put some on the terminals and the ends of the batteries.

Oh, and don’t buy batteries at the dollar store. They are not worth the money you save.
Buy a name brand.

Finally, I’ve found that buying batteries online is sketchy at best. Sometimes they are at or past expiration. Some come loose packed (not in original card packages) - I think those may be rejects, or possibly used. I now only buy batteries from retail stores (Home Depot, COSTCO etc),

You can thank me later!

(Note on my comment regarding used batteries. Many companies replace batteries in their devices on a schedule, rather than waiting for them to die. This results in a box of used, but not quite dead yet batteries, which I suspect find themselves somehow on Amazon, EBay etc.).

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Rich6006

9 months ago on Step 2

That's what happens when you use Duracell batteries. Great way to clean up the mess that they leave though.

Thanks for the helpful tip.

1 reply
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RicksterInstructablesRich6006

Reply 5 months ago

That’s odd. I’ve never seen a “copper top” leak/corrode and now use them (or the new quantums exclusively.
I’ve seen way too many pink bunny battries leak...

When I buy something (like a TV remote) that comes with batteries, I always throw those questionable,ones away and use copper tops.

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ZaRue

5 months ago

After using a 'bath' and then file to remove the offensive corrosion, I have found it helpful to 'tin' (coat with solder) the contacts. So far, no further damage has been caused by any leaks after using this method of 'sealing' the contact.

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LesB

9 months ago

Best solution:

DO NOT USE ALKALINE BATTERIES.

Period.

Well, ok, I do use them on cheap throw-away devices.

For any device that one values use LITHIUM batteries. These do not leak. I have not had a lithium leak in the (15?) years I've used them. Plus, they are just plain better.

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RubensS2LesB

Reply 9 months ago

Just to be careful with 3.6V AA rechargeable lithium batteries like 14505 or LS14500 non rechargeable ones... For even batteries appliances there are '"dummy" AA cells tha allow using these lithium ones (50% real batts, 50% dummies...). Of course there are 1.5V Lithium AA, with built in step down converters (3,6v --> 1.5V), for both rechargeable or non ones...

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LesBRubensS2

Reply 5 months ago

Lithium batteries come in standard AA and AAA sizes. The voltage is slightly higher than Alkaline, I think 1.65V.
You are thinking of Lithium Ion, which is the rechargeable version. I'm referring to the plain lithium which are not rechargeable.

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RubensS2LesB

Reply 9 months ago

Also be careful with fake Lithium coin cells... I've got a "CR2032" (leaked into a equipment) that was in fact 2 alkaline (?) cells in series, performing 3.0V or a bit more new. They leak.

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JohnC430RubensS2

Reply 9 months ago

That's great advice. However, Lithium batteries are 3.7V and come in odd shapes compared to the Alkalines. so they don't fit physically or electrically. 1 battery voltage is too low and two becomes too high so u need 2 batteries with a voltage regulator. so although the suggestion is possible it is not very practical. I have had to do just what I said for some of my small projects.

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fattG

5 months ago

The Chinaperson who sells little terminals does not ship to USA.

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Zaphot

9 months ago

a "Glass Fiber Eraser" is a good tool to remove oxidisation and corrosion too...

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lonesoulsurferZaphot

Reply 9 months ago

Cool - thanks for the tip! Never heard of these before. Just got myself one from eBay

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richfiddler11lonesoulsurfer

Reply 5 months ago

Oops missed this comment and recommended the same thing above... in any case +1 for the fiberglass scratch pen/brush, it’s an indispensable tool for cleaning contacts! Pro grade electrical contact cleaner is also good to have on hand (mostly for volume controls/pots/rotary switches, etc.

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richfiddler11

5 months ago on Step 1

Great instructable! I’ve been cleaning devices with corroded batteries for years, but never knew the chemistry. From now on I’ll definitely neutralize with vinegar.

One tool I’ve found invaluable is called a “Fiberglass scratch brush” or pen. It’s a bundle of fiberglass strands in a (bulky) pen form factor and does a terrific job of removing the crystals and corrosion without damaging the surface (as would a file or sandpaper). You can find many on amazon, etc by searching for the name above, they run about $10.

It’s funny, for years I hadn’t seen many leaky batteries, but within the last 5-10 years it’s been much more common. I’ve heard this attributed to the rise of inexpensive alkaline batteries that cut corners in design and manufacture to save money. I still use cheap batteries, but I try to remove the batteries from anything that might not be used for awhile.

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henryharp

9 months ago

I have been using a very simple method for 65 years and my parents used this method before me, so I don't know how many years this has been common knowledge. I have never failed to permanently restore even the most corroded terminals on vehicle batteries or any other battery-dependent item. It is a three-step process: take some regular cold, very strong black tea, pour it on the terminals as you scrub with an old toothbrush. Let it dry, and then coat terminals heavily with vaseline. Put your new batteries back in. I have never had to dismantle any mechanism, and have had 100% success using this very simple method.