Ever Ready (Leclanché) Cell

[60 oldjohn]

Any one know anything about this Cell ? Were they sealed ? I have seen another on this site but it appears to be taped up in recent times. How would one of the electrodes be supported? at present it is just laying at an angle clearly not right and the jar has a moulding at the top for this electrode. When were they made ? were they accumulators ?


John.

[Cobaltblue]

It's a Leclanché cell

It's exactly as it should be.

The the liquid should be salamoniac

The rod just stands up un supported not usually at such a jaunty angle

Cheers Mike T

[Ed_Dinning]

Hi John, an early Leclanche cell as used for household bells etc. Many were just like that and unsealed. Not rechargeable unless you replace the chemicals
Zinc rod (neg) normally had a terminal on the top or a wire soldered to it.

Electrolyte was ammonium chloride solution.
Should be plenty of detail in 1920 electrical books

Ed

[Philips210]

Hi.

There is the same type of Leclanche cell shown here http://www.ssplprints.com/image/8256...ver-ready-1957 and that particular example was made in 1957.

Regards
Symon

[bionicmerlin]

Hi . I have 6 of them . I also have the bell board and bell they were powering.

They were
removed in about 1980 . At the time my boss said to me they would only supply power for a short period of time then had to recover, hence ideal for bells. Not sure how true that is as I have never used them. A few years ago I did get hold of some new zinc rods as my originals were almost corroded away. Just in case I ever want to try them.

Andy

[Herald1360]

Yes, they get polarised quite quickly causing the voltage to drop. They then need a while to recover.

[Ed_Dinning]

Hi Gents, a study of the chemistry of the cell shows that the porous pot contains manganese dioxide as a depolariser as well as carbon granules to reduce cell resistance.
I think the manganese dioxide acted as a catalyst, so should not get used up, but worth looking at.
Top of porous pot was normally pitch sealed and a line of pitch was applies round the lip of the glass jar to prevent the sal ammoniac "creeping".

It may be that the bells drew a heavy current that the depolariser could not immediately cope with

Ed

[kalee20]

I've played with them as a teenager in the 1970's.

The porous pot contains manganese dioxide. The zinc rod gets used-up according to ampere-hours consumed.

Th electrolyte is sal ammoniac (ammonium chloride), 2oz to a pint of water (ideally distilled water or clean rainwater) to stop any side-reactions.

They work well, but are indeed best for intermittent use, same as carbon-zinc dry batteries (which use the same chemistry).

The manganese dioxide is a 'depolariser' and acts to remove gas generated at the carbon plate, which is the negative electrode. If it wasn't there, hydrogen would be generated, the minute bubbles of which would stick to the carbon and insulate it, stopping current flow. The manganese dioxide oxidise the hydrogen to water. So it eventually, too, gets used up. That is why the cell cannot be recharged - in principle, zinc can be plated back onto the rod, but manganese oxide can't be electrolytically converted back to dioxide.

[broadgage]

These cells could produce a very small current continually, as well as bells they were used for railway signals and intruder alarms, both of which required a small current 24/7.

They were not electrically rechargeable but were re-usable by replacing the active materials.
The zinc rod should be replaced when largely dissolved, and when cell fails to work properly the electrolyte should be dumped and replaced with new.

The other components should last almost forever.

These cells were normally known by their total volume, the most common being the "quart" size but larger and smaller ones existed.

Unfortunately suitable zinc rods are no longer available. Zincs for Leclanche cells were treated with a little mercury rubbed onto the surface where it forms an amalgam with the zinc. This is out of favour due to the toxicity of mercury.
Plain zinc rods are readily available and work to an extent but tend to dissolve even the cell is not supplying current, due to a phenomena known as "local action". Different parts of the rod have a minutely different electrochemical potential, resulting in a local chemical reaction that dissolves the zinc.
The amalgamation with mercury retards this.

[kalee20]

Good point on amalgamating the zinc to prevent local action! Though I can't help feeling that this was a cheap way of using commercial zinc. If suitably pure metal is used, it won't be necessary...

Originally Posted by broadgage

The other components should last almost forever.

That's the only thing I'd disagree with in your post. The manganese dioxide in the porous pot is not a catalyst, it DOES get used up oxidising hydrogen to water. However, there is usually plenty of it, (mixed up with carbon granules as Ed says, to effectively make a conducting matrix in intimate contact with the dioxide). I'd guess symptoms of it being exhausted would be that the cell sags heavily after a few moments use, taking ages to recover.

I'd urge the OP to try using it! Ammonium chloride is not expensive - I still have a jar I bought from my local chemist. That's all that is needed, (plus deionised water ideally).

When in commonplace use, I believe the porous pot/depolariser/electrode assemblies were shop-bought replaceable items. Obviously now obsolete - but manganese dioxide is available from a chemical supplier, and melting off the pitch seal, cleaning out and replacing, should give hours of fun...

[broadgage]

Regarding the manganese dioxide, my understanding was that this lasts almost forever and would not normally require replacement.
I thought that it reacted with the hydrogen that would otherwise form an insulating layer on the carbon rod, but that this reaction was slowly reversed by atmospheric oxygen.

Whilst replacement porous pots complete with contents were indeed sold, my understanding was that this was to replace breakages, or to construct a new Leclanche cell in say a glass pickle jar rather than purchasing a specially made vessel.

[Techman]

Good, clean battery fun!

I've got a few of these in the collection - just add water and off they go, well hopefully, as it's been a few years since I did.

As can be seen, the one in the original flimsy brown paper wrapping has never been used, plus there's a spare innards. Several of the porous pot innards are date stamped, but I wasn't going to unwrap the polythene to investigate all of them as they're likely to be a bit messy - even if they have been dry for years. Time for some water and volts - or perhaps not just yet. I've had the unused one and its spare innards out on display so it's got a bit dusty and that one will be kept as-is as a collectors item, as I've got the others to play with if need be.

Pics:-

[Dave Moll]

Originally Posted by kalee20

...the carbon plate, which is the negative electrode.

Is this really the case? With a dry cell, the central carbon electrode is the positive one, with the zinc casing forming the negative electrode, and as has been said earlier in the thread, these employ the same chemistry as the Leclanché cell.

[broadgage]

The carbon is the positive and the zinc is the negative in both an old type wet Leclanche cell and the newer dry cells.

[kalee20]

Originally Posted by broadgage

Regarding the manganese dioxide, my understanding was that this lasts almost forever and would not normally require replacement.

I thought that it reacted with the hydrogen that would otherwise form an insulating layer on the carbon rod, but that this reaction was slowly reversed by atmospheric oxygen.

It does react with the hydrogen evolved, yes, by supplying oxygen to form water. (MnO2 + H2 -> MnO + H2O - or possibly 2MnO2 + H2 -> 2MnOOH)And it would be lovely and elegant if it was reversed by atmospheric oxygen. But it isn't.

However, the amount that is present could well be enough to last for many years, so making replacement an extremely rare event!

Originally Posted by Dave Moll

Is this really the case?...

Oops! Nope! The carbon IS the positive!

[TonyDuell]

The carbon is the positive terminal of the external circuit, but I seem to remember that from the point of view of the chemical processes in the cell it's the cathode, as it's where electrons enter the solution.

[broadgage]

Does anyone know of a source for new or NOS wet Leclanche cells ?

Not valuable or collectable vintage ones, but suitable for use. They are allegedly still used for railway signalling in a few places, but I can't find a supplier.

[Dave Moll]

In what situations would a wet cell have a practical advantage over a dry one?

[greenstar]

The impression I have is that wet cells, if maintained, last for donkey's years as broadgage says. I have a couple of ancient ones, maybe 1920's, that were completely dry, added sal amoniac, and they work well. So I would think in a situation where you didn't want to keep replacing dry cells, and you had people nearby to top them up, or replace the zincs, they would have an edge and be more economical..

[Refugee]

Most modern remote locations now have a small wind turbine and solar panel with Li Iron batteries. Road signs are common with this arrangement.