Introduction

Suggestions to use lemon juice (or vinegar) on battery terminals damaged by leaking batteries –usually RC transmitters in our case – have been around for some time, but I didn’t have anything to try it on.

This week I bought a used FlySky FS-iA6 combo on eBay, and while I can’t fault the seller’s packaging or speed in sending, I really did need to do something about the corroded terminals.

 jr lemon 001 jr lemon 002

 

Theory

The basic idea is that by using a weak acid – vinegar or lemon juice (pH 2.7 to 3) are the varieties most likely to be in the home - to neutralise the alkaline (pH 10 to 11) electrolyte. 

This primarily applies to the alkaline batteries that leave crystalline deposits and blue/green corrosion in our radio gear, but Ni-Cd (nicad), NiMH (nickel metal hydride), and Zinc Carbon batteries also use an alkaline electrolyte.

This obviously won’t work for the lead acid batteries used in large boats and the biggest land RC vehicles. It also doesn’t apply to rechargeable lithium-based batteries as their electrolyte is also acidic (though I’ve yet to see a Lipo battery leak electrolyte).

Button cells can also leak, but whether you can use lemon juice on them is going to depend on the exact type of battery. Internal chemistry and the electrolyte can be wildly different on the inside, even though cells may look similar on the outside.

Method

I decanted a small amount from off-brand bottle of lemon juice into the cap, then sucked it up into a syringe so I could apply it one drop at a time.

jr lemon 003

I dropped just enough to cover the affected area and observed fizzing almost immediately. After a minute or so, the reaction died down and I removed the liquid with tissue. Repeated applications resulted in a less vigorous reaction, until the fifth did almost nothing.

jr lemon 004 jr lemon 004

 

I rinsed the contacts off with clean water, dried it off as well as I could, then left the transmitter back near a radiator for an overnight low bake.

In the morning I used a fibreglass pen to get back to shiny bare surfaces at the important points, but it’s plain to see that this method is not going to restore battery contacts to an as new, or even visually good condition.

jr lemon 006 jr lemon 007

 

I also tried lemon juice on the contacts of a much older radio set (Acoms AP-227 “mk. I”), without success. I cleaned this many years back (fibreglass pen, debris removed with air, followed by a scrub with Isopropyl alcohol). Verdigris has grown since then – and an application of lemon juice this time around did nothing to remove it.

jr lemon 008

 

pH Tests

I remembered that I had a pack of universal pH test strips after doing the cleaning, so could only test for alkaline deposits by swabbing the (clean looking) inside of the front of the transmitter case. 

This showed a pH of nine (or ten at one edge) but I would expect encrusted contacts to show higher due to being undiluted.

The second image shows the acidic nature of the lemon juice – pH 2 to 3. 

The final image shows a swab of the cleaned contacts – pH 7, neutral.

jr lemon 009 jr lemon 010 jr lemon 011

 

Conclusion

Based on the fizzing reaction and the pH testing, lemon juice neutralised the alkaline deposits, potentially halting any ongoing damage and making future handling safer. It also did an excellent job of removing fresh blue/green crud and electrolyte crystallisation. 

On the other hand, it didn’t do anything about the damage done by a leak, or a previous incomplete cleaning attempt. In fact, the results can look worse due to there being nothing to hide them.

The fact that it’s a “wet” process – rather than scraping off deposits and risking them pinging off into dark corners, or eyes – must be a good thing, as does any residue collected being (at least closer to) pH neutral. 

Whether it will work on old but untouched leak residue, for example, buying an old radio set that still has the failed batteries from 1980 something still in it is something for the future.

On balance, I think I would do this on any future instances of battery leakage I happen across, because the worst that can happen is nothing. 

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Written by TB member Jonny Retro

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