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Old 9th Aug 2018, 5:01 pm   #12
kalee20
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Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,059
Default Re: Nickel Cadmium vented cell battery, advice sought

Definitely agree with Argus on safety with KOH!

Potassium hydroxide (and sodium hydroxide) also turn fats and oils to soap - if you have a drop of solution on your fingers it immediately feels soapy. It is worth having a good quantity of weak acid available, to neutralise spills - cheap vinegar is fine. (Why should the acid be weak? Well, to be sure of neutralising any spills of alkali, you want an excess of acid - but if you have an excess, you want the surplus to be non-aggressive, which vinegar is. Note that weak acid is NOT the same as dilute acid; a weak acid is an acid whose molecules take a lot of persuasion to behave like an acid, such as only when attacked by a strong alkali; so when the spilled KOH is all neutralised, any remaining weak acid is relatively safe).

I have seen Edison NiFe cells very similar to the OP's photographs! I have never seen a wet NiCad like this - but I believe they existed. Construction would have been very similar and the only way of telling them apart would have been the labelling. So, the OP could have either types of chemistry, and I reckon that charging them and measuring the voltage is the only way to tell apart. I believe that NiFe has a higher self-discharge rate but it was cheaper, and also has a higher terminal voltage (around 1.5V as against 1.25V).
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