Battery Tester

That sort of testing is built-in to many chargers, e.g. mine is pretty old-hat, but will do a discharge/charge cycle, or can vust measure cell voltage

eBay still sells them, but most seem to be USA imports (beware expensive duty?)

some of the "smart" chargers do something like that before they start charging, although I dont think many of them handle lithium batteries

I have an "older" non smart charger which sometimes brings them back to life, possibly on account of a very low and constant charge current

I had one of those, but I was never convinced the refresh/test was useful. It broke eventually, after 7 years. My latest one was very basic, £10 USB powered.

I also use a tester:

New batteries are pretty cheap.

Me too, even when the refresh one wouldn't, but I think the sensible thing to do is throw them away the moment you suspect they are problematic.

thats one approach ...

but I suspect that my smart charger might be a bit too picky sometimes.

If it tells me that a cell is knackered then I leave it in the slow charger for a couple of days and when it gets back the smart charger usually changes its mind - most of the time they dont seem to suffer from the experience

For quick and ready, I use my "shaver test." I know what it should sound like with a set of good batteries so I swap them in and out and weed out the failing ones.

As the batteries fade through use over time, they get reduced to less demanding operations. Camera and motor (and DAB radio) batteries get demoted to other equipment as they fade until they end up in the bathroom AM/FM radio which seems to keep working on little more than a trickle of juice. Then it's off to the great battery graveyard in the sky - aka Lidl/Saino's recycling bins.

Nick

One way is to bodge a good cell in parallel with one that the "too smart" charger refuses to charge, just until the cell voltage rises a little ...

or ... if its an AA cell .. I can sometimes hold the cell against the contact for a C or D cell in the smart charger for about 10 seconds

I am not completely sure what this does but it sometimes frightens the cell in to behaving itself

I've had this with 12v lead acid batteries. My smart charger will reject them if it senses that the battery voltage is below some arbitrary level. My old dumb charger will put current into anything you connect it to, and has more than once 'restored' an exhausted battery to the point where the smart charger finds it acceptable. The battery has gone on to give useful service for an extended period.

I've had one like that for years (from 7dayshop), although mine has an analogue meter instead of the led display. I thought that they were only of use with non-rechargeables, as they were designed for testing 1.5V batteries.

My way of squeezing the last drop out of AA & AAA batteries (rechargeable or otherwise) is to put them in a set of LED 'candles' I place in odd corners upstairs . They operate on a built-in timer, and give just enough light for those middle of the night journeys.

around here most houses have that new fangled electric lighting stuff :-\

Yeah 1.5v, and you don't get all three green bars with a 1.2v NiMH, but you do get 2 green bars.

FWIW, you do get 3 lights on if you take a NiMH out of my GigaSet VoIP phone, because it over charges/cooks the batteries and indeed they only last a year

If I really cared I could use a voltmeter. Normally I'm happy that 2 bars means they should work. Cheap and cheerful. My point was that in practice the greater stats from a smart charger were not really useful in an everyday sense. The smart charger took many hours (days) to tell me the capacity of a battery, then I would forget which was which.

Flash in the pan. It'll never catch on, I reckon.

(When you get to my age, you look better by candlelight.)

I have a smart charger like that. If I run the batteries down too low the smart charger indicates it is faulty. However, I have an ancient low current charger (16 hours to fully charge AAs in 2s or 4s, no odd numbers) and if I bring the batteries back into part charged with 4 hours or so in that, the smart charger will then happily continue the charge until full. My smart charger charges each battery separately, and it signals fully charged separately for each battery. Because of that, I can mix AAs and AAAs despite their different charge capacities. I can mix NICADs and NIMH too. It doesn't charge lithium batteries though.