NiMh Cell: powdery coating under plastic sleeve

[Nick Odell]

One AA cell has suddenly turned grey underneath the transparent printed sleeve and it looks like a powdery coating has formed there.

Under normal circumstances I would just throw it away but these are not normal circumstances (I´m about 8000 miles away from my stash of spare batteries and over here I´m not allowed out to buy any more) so I´d like to keep using it for as long as it holds a charge if it is safe to do so and it will not ruin my equipment.

Any thoughts about whether this might be just corrosion on the outside of the can or might it be leaking chemicals or is something else happening?

Thanks!

Nick

[Brian Gaff (Sofa 2)]

Is it under the top bit? It I believe has some seals or pressure release system for when it overheats. I imagine its better than it blowing up! Brian

[tabbypurr]

usually means it's leaking, and the leakage is corrosive. In your circumstances I'd keep a close eye on it.

NT

[Pamela]

[newshound]

I think Pamela is right, it is a leak and on its way out but in your circumstances I would probably keep going. The sleeves seem pretty robust. I don't think it is likely to overhead and blow up like a Lithium Ion.

How valuable is the kit, and do you stop earning if you stop using it?

If it is a preamp for a guitar active pickup (say) then the worst consequences of failure might be corrosion and a requirement to replace the battery box. Hard to see how it would destroy a guitar but it might wipe out something more compact, say a radio mic.

Is "over here" somewhere that you can't even order stuff online? Can you get "ordinary" AA's? Assuming it is in a multi battery rig then the "extra" 0.3 volts if you replace just one is unlikely to fry anything.

[Nick Odell]

Seems to be going okay so far....

Ooops!

(Thanks to everyone for your replies. Appreciated.)

Nick

[The Natural Philosopher]

Dont worry., he is talking through his arse. All the changes that happen under [over]charge happen INSIDE the cell.

Issues outside the cell are down to surface chemistry alone

[Pamela]

You're probably confusing the white residue with potassium carbonate leaking from alkaline cells.

[Pamela]

[Nick Odell]

That mention of overcharging concerns me. I thought all chargers these days automatically cut out when the battery was fully charged or after a certain period of time had elapsed? I am currently (sorry about that) using a two-cell usb-powered charger from Screwfix which blinks while it is charging and shows a steady light when it has stopped. (Most of) my other cells run to the end of their charging cycle and then stop. These ones, I admit, just go blinking on and on.

Nick

[Nick Odell]

Not able to order anything on line. Even in the best of times on-line ordering still meant on-foot collecting which at the moment we are not allowed to do. Even so NiMh cells are comparatively expensive so I guess I will have to use supermarket alkalines if I have too many NiMh failures. I do not forsee any problems there - unlike the time I destroyed a perfectly good film camera by putting rechargeables in the compartment clearly labeled "use alkaline cells only." I told uk.d-i-y about that at the time.

"Over here" is Buenos Aires, Argentina where I will probably be for the next few months. Apart from the pocket SW Receiver (3x AA) and the electric shaver (2x AA) it is mainly photographic equipment, including a medium format film camera which uses 8x AA cells in the motor drive. I have had to take a different spin on photography: since us over-65s are not allowed out of the house under any circumstances, instead of stuff like wandering around railway sidings photographing old trains, it has become a matter of trying to find new and interesting ways of looking at whatever I can see from the balcony.

Thanks for all the advice,

Nick

[tabbypurr]

There's also the world of macro. Don't even need equipment for it, can make extension tubes from cardboard. Nothing moves so manual lens control is workable. Ring lights are useful but not essential, there are ways to bodge one from card. You probably know all that. Perhaps you could pay someone to bring you some NiMH from a local shop.

NT

[nothanks]

(Apologies for thread drift) Could this be the same Nick Odell who appears in

after about 9 minutes? I've made a few instruments (dulcimer, mandolin, Tenor Guitar, Melodeon, and Hurdy Gurdy and restored a few others). The aim is to eventually make reproduction English Guittars, if I can ever get rid of everything else that needs doing.

[Nick Odell]

Yes, well... Can not use cardboard with the medium format camera since it has a leaf shutter between the lens elements and needs an electrical connection to fire it. But I have a Pentax SLR and DSLR here for which the lenses are interchangeable and I have a macro lens in my kit.

My other half comes from here and lives here most of the year and today the task will be to d-i-y a set-up to digitise some old slides from her childhood. Of course back at home I would have put them in my

9600dpi Canon scanner but for some reason which escapes me now I did not think to put that in my luggage before I left Dear Old Blighty.

Nick

[Nick Odell]

Oh dear: I am afraid you have me banged to rights there. I have been retired now for quite some time and although I have had ambitions to turn a basement room into another workshop, details like boomerang kids at home and spending too much time down here in South America have kind of got in the way. Maybe if I ever manage to get home again and maybe if being in lockdown in the UK becomes an ongoing thing I can get those ambitions back on track.

Delighted to hear about what you have been building. I have enjoyed building reproduction historic instruments myself. Mainly as an exercise to experience how early makers used to work.

There used to be some good usenet newsgroups for instrument makers but I am afraid they seem to have gone the way of so many other good groups. Still: at least uk.d-i-y is still thriving!

Nick

[tabbypurr]

You don't need a shutter to do macro. A black cloth & very low lighting works. Film is as you know tolerant of off exposure to a sufficient extent. Crude yes, but it works, and doesn't imply low quality results.

NT