How to Fix Corroded Battery Terminals

Intro: How to Fix Corroded Battery Terminals

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

Comments

[lonesoulsurfer]

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.

[ruggbg]

THE best thing I have found to remove this corrosion is VINEGAR. Cover everything with it for about 5 to 10 minutes, then brush it off with a little water. You may need to scrap the contacts clean if the corrosion has been there too long. It amazed me how well it works. If you can't take apart the item and you get some vinegar and water internal to it, just make sure you let it dry COMPLETELY b4 applying power again.

[NitroC]

Hello I had a question this is my father's basically antique ohmmeter or multimeter and it worked not a month ago and I just tested a few batteries in the house trying to get to know how to use this I get many manuals from online how to store it properly and everything like that took it out to use it today didn't work didn't seem to read anything I didn't read that it had batteries and sure enough this is what about what led me to believe I see it was a little bit of white dust inside the clear display. The leads and everything are connected and all the blue dust and white dust was definite there before I did I just I'm devastated because my father definitely took care of this and made mention to take care of it of course I did like three at most but you can tell these batteries are very old they are 2014 expired Gucci batteries are about 10 years before anyway these batteries in this situation I just wondered does it look really bad and do I have to use vinegar and everything to get rid of this should I act now or just kind of clean away with a brush get two new batteries and see if it works? I had several small devices happen this way and I just remove the batteries in kind of filed away or any rust usually but didn't know I had to go to any extensive measures to get the device working again and I have to reiterate this is definitely A prized possession of my fathers and is an antique and well-known online it's not worth much but I'd rather just get this taken care of and not even let him know lol. Love the video or the instructional guide and definitely the best online because videos don't always suit everybody for like learning and stuff so I just wanted to ask anybody to be any advice if I have to go to the extent of using vinegar which I have here or can I just dust it out? Scrap/ file the metal connectors? Yes I said this work not even a month ago and it was stored in bubble wrap in plastic and everything like the way it was given to me so I didn't know if this was something I did or just old batteries and device I guess? The white dust in the casing is definitely new and kind of noticeable and the blue stuff looks a little fresh? I know I just blew on it and it got in my eyes because I am an idiot I guess. I just wanna proceed with caution because this is a pretty precise measuring device and don't want to go at it like I would an old TV changer or something like that any help would be greatly appreciated thanks so much

[RicksterInstructables]

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.).

[Dave1ssi]

This is it right here. Couldn't agree more that Caig De-oxit is the best product to clean and support battery terminals, switches or contacts. Been using it for many years. Clean up the nasty bits with vinegar and a small brush, use denatured alcohol to clean up anything else and top it off with De-oxit. Do not use water around your battery terminals or electronics.

[Rumplestilkson]

I have used De-oxit for years in my 2 way radios, flashlights, department pagers, scanners, and ham gear, never had a battery problem. Of course with my flashlights, I replaced the batteries every spring and fall wither they needed them or not, usually much sooner, used for volunteer fire/rescue work.

[Rich6006]

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.

[RicksterInstructables]

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.

[Jiyu]

All alkaline batteries will eventually leak if you store them in a warm humid place. I've had to have Duracell replace two entire 40-packs of AA batteries because they were stored in a laundry room. They replaced them immediately at no charge. Still my favorite brand.

[RaymondR6]

The Duracell "copper tops" do leak. I have four from a battery powered lamp that I had to replace yesterday.

[skylane]

ALL brands will leak, eventually.
Duracell and Energizer brands will replace a damaged device due to leaking.

[henryharp]

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.

[lonesoulsurfer]

Nice - I'll have to give this a try!

[JohnK241]

Hentyharp hasn't come across some of the vehicle terminals I've seen! Black tea won't replace lost metal. I'm curious to see how it performs on less radical cases, though. Great to see so many fellow 'rescuers' on here. I do hate the bin it & buy new culture.

[Jiyu]

Actually, it will. The tannic acid in black tea will (eventually) reduce the oxidized metal back to base metal again. But the amount of tannic acid in black tea is extremely weak. White vinegar will do a much better job, much more quickly. In a pinch, you can also use the carbonic acid in cola or any other soda pop. It will work better than the tea, but not as well as vinegar.

[DonnH1]

Black tea would contain some acid which could help neutralize an alkaline liquid but your choice of Vaseline to protect may be a bit flawed. It is a product which can and will migrate once it is warmed up. It goes from being a thick lubricant to runny. I was introduced to something called anti-oxide battery grease and it was used to protect start battery terminals (batteries for starting large diesel electric plants). Anyway it is quite tarry. It may even have something in it to keep it in place like some sort of fibre. I have used it for years on my own automobiles and once applied I never again have to clean, scrape, or wash off the terminals. You need to treat the nuts and bolts too. Yes it would work on other things like flashlight battery terminals. One other area people don't think about is turn signal lights. Water containing salt gets into the sockets of turn signals during the winter, the stuff used to make the roads safe to travel on in the winter. The thing to do is smear something like silicon grease all over the light contacts and socket contacts and put the bulbs back in. That will stop corrosion in those lights. I just Googled anti-oxide battery grease and a Amazon item came up. It was No-OX-ID in an 8 oz tube. That would probably last a long time. There are similar products. I have no idea who made the stuff I was using.

[RaymondR6]

See my post on using light mineral oil. It is easier to use than greases.

[DonnH1]

I have an ultrasonic cleaner I purchased through Amazon for a fairly reasonable price. I throw electronic parts to be cleaned into the bath with some white vinegar and water. It cleans them up very well. It was a great investment. If you can remove a battery holder and drop it in the bath that helps. Afterward you can replace the vinegar solution with just plain water and run the machine for a rinse. I sometimes use it to clean coaxial cable parts. I live in an area where there is sea air containing a small amount of salt harmful for coax cable connectors and antenna parts. The ultrasonic cleaner helps with that. Also cleans my wife's jewelry and makes it shiny again.

[bpark1000]

The corrosion products are usually alkaline, not acid. To dissolve the corrosion, you need acid, not alkali (baking soda is alkaline). The best acid to use is hydrochloric acid, available as a pool pH adjustment chemical and brick/concrete cleaner. If you use that, you need only a thimble-full diluted in a few ounces of water. You can also use vinegar with a little salt added. After you dissolve away the corrosion, first rinse well, then use the baking soda solution to neutralize the acid. (Do not mix soda with acid. That just destroys the acid and makes fizz. You want to let the acid do its job first.)

For equipment with integral battery compartments, hold the item with compartment facing down, and apply chemicals/rinse from below with cotton swabs to minimize chance of getting chemicals in the electronics. Dry everything completely before closing up the equipment, preferably overnight. Preferably, remove batteries when not using equipment. When equipment has batteries in it and it is not being used, store with battery compartment facing downward. Modern mercury-free batteries burst and leak, often before you even have a chance to use them!

[Jiyu]

Hydrochloric acid is much too strong for cleaning up alkaline battery corrosion, and is very dangerous to handle. The acetic acid in vinegar works just fine, doesn't require diluting, and is perfectly safe to get on your skin (but do protect your eyes).