Testing alkaline batteries Featured

Most articles suggest a brand new alkaline battery starts at 1.65V o/c and goes down from there.

Do you have reference you can cite for a well used one with a o/c voltage of 1.8V?

The only odd circumstance I can think of will be a duff meter.

no, haven't looked.

I told you what the circumstances were. The meter's fine. But feel free to get stupid again.

NT

But it's you that said it will kill the DVM...

I have and 1.65 is the highest I saw for a new battery. An old battery will typically be < 1V.

Perhaps it was user error then, or not recognising a malfunctioning meter?

If you have any non "stupid" reason for the erroneous measurement, please do let us know.

I see some consistency here, where the facts are bent to meet opinion.

Have we no electrochemists in the house ?

(+) electrode:? 2 NiO(OH) + 2 H2O + 2 e? ? 2 Ni(OH)2 + 2 OH? (E0 = +0.50 V/SHE)

It's a redox reaction with two half-cell potentials, that give the overall battery cell output voltage.

Was this battery mixed in with a lot of other batteries ?

Or did some other battery type leak, electrolyte got between the inner cell metal jacket and the outer shell steel covering ? The multimeter would need to be touching the outer steel covering, instead of the tab on the end, to (somehow) tap into the phantom voltage.

It makes more sense that it was a purpose-built NiZn cell.

Paul

In message snipped-for-privacy@davenoise.co.uk>, "Dave Plowman (News)" snipped-for-privacy@davenoise.co.uk> writes

And if the fuse is a 'special' (like in my Fluke) it's rather expensive. [I think mine cost eight pounds.]

Well spotted!

The 1.8v muppet was talking about *rechargeable* alkaline batteries when everyone else was discussing single use primary alkaline AA batteries.

I have never seen a battery whose voltage increased significantly with use as its remaining capacity decreased. YMMV (but I expect that it doesn't)

Rechargeables can increase their voltage when discharging, I have a discharge tester that shows voltage, current and capacity as it runs and you often see a (small) increase in voltage at the beginning of the discharge cycle.

If this happens, why? If has cooled down after charging, possibly the effect of warming up a little?

The reduced voltage is a consequence of temperature increase and the corresponding reduction of terminal voltage. It is often used to determine the charge end point.

Oh dear, did you find out the hard way?

I suspect the reason is the voltage rating of the fuse and arc suppression.

This can happen if you don't:

I just decided to buy a spare to fit into the little slot in the case!

About a tenner, as I recall.

Yup. Makes you take care. ;-)

these weren't new batteries

no

the measurement was not erroneous. Did I not already mention the cells had just been recharged? Short term overvoltage after charge is a routine phenomenon. Any EE knows this. 1.8v is unusually high but there ya go, consistency is not something that happens with post-charge voltage. Did we not cover this already? Yes I did:

NT

it was a recharged alkaline or ZnC.

No you didn't. Unless you're a sock pretending to be someone else and think you have?

Any EE would know that the alkaline batteries referred to by Scott and myself were primary cells. Rechargeable alkaline never caught on for being so poor in so many ways.

You might well have done, which can only be explained as an entirely different chemistry to the standard alkaline battery discussed here.

You never did answer the question, "Was this battery mixed in with a lot of other batteries?"

A good rule is don't let your insatiable desire to be right get in the way of facts. The alternative is to look a plonker.

Please do give more details.

So not a battery that any EE would refer to as alkaline.

You've excelled yourself at being an idiot. The batteries in question were alkaline. They had just been recharged. That's it. It doesn't get any simpler. If you still don't understand the situation, I have ceased to care.

NT