I have a small problem with my cell charger. I think I know what the problem is! When I put a couple cells in my charger to charge only one charges.
If I take them instead to an older battery charger that charges two cells is series, then they charge, and after just a few minutes, I can return them to the single cell charger, and both charge.
What I assume is there is some device in the cell charger to stop charging cells inserted the wrong way around. I guess where a cell is completely flat or reverse charged due to one cell being better then the cell charger assumes wrongly inserted, and will not charge it.
I have come across this with large battery chargers for lead acid batteries but not NiCad and NiMh before.
I have been careful to select cells of same type, and make, with the same mAH rating.
I knew about the problems of crystal growth, and at first I had assumed I had a bad batch of batteries with crystal growth, however since the charger which will start charging them is a slower charger then the one that refuses, I am reasonably sure it’s not a crystal growth problem.
The charger which fails is a fast delta voltage type charger. The one which charged them is still a fast charger with a time out, but no where near as fast as the delta voltage one.
Clearly now the problem is identified all I need to do is start the charge with another charger, but I was very near the point of binning the cells when there was nothing wrong with them.
I am also having problems with batteries which have been flat for a long time with the delta voltage charger. It signals them as charged in a very short time. Pressing the discharge button seems to cure the problem. On second charge they seem to charge OK.
Only got the delta voltage charger beginning of November, so only been using it for one month. I got it as it will charge 10 AA cells at the same time, and they do not have to be inserted as pairs. Which when one has items using 1 or 3 cells is far better. Did not realise it was a delta voltage charger until after I bought it.
So there are two reasons for post.
1) Let others know so they don’t bin good batteries.
2) Find if other have had the same problem.
Next time I get a cell fail I will stick a meter on the cell.
The instructions seem to be general, not particularly for the charger I have, as it says unplug after charge completed on box, but it has a trickle charge to maintain the cells in fully charged condition according to write up. So I am not 100% sure which instructions are general and which are for this model. It says 250ma which from time taken to charge an 800mAH cell in about 4 hours seems about right.
My wife has bought most of the AA cells when see sees them going cheap. She loves bargains even if she doesn’t need them. Most the cells are quite a low mAH rating. 600 and 800 are common although there are a few 2500 among them. Only noted the problem with the low capacity type, but this may be because I tend to use the low capacity in items like my keyboard which uses very little power and I don’t change them until it fails.
So is this a normal problem or is my charger faulty?

in general you must only ever charge a battery with the correct charger
you cannot charge different chemestry batteries unless the charger allows this
each needs chemestry needs different conditioning
old batteries and old chargers will fit new batteries and new chargers but should not be cross used unless you know the combination is compatable

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we are all ------------------still learning

The charger is designed for both NiCad and NiMH batteries. Clearly the cycle button which will discharge a battery before charging is only for use with NiCad batteries although it would not harm the NiMH type. The only battery one can't charge is the Alkaline rechargeable as the voltage is too high 1.5 volt not 1.3 volt. There is a safety in case a non rechargeable battery is put in the charger so if the voltage goes to 1.5 volt the lights flash this happens if I in error put the Alkaline rechargeable in the slot.

But the two problems either will not commence charge or very short charge I think are because of reverse polarity safety circuit and the delta voltage charging method of completing the charge cycle. I am guessing just something I have to live with?

But interested to see if others have the same problem?

I have an old delta voltage battery charger that was to charge walkie talkie batteries and I seem to remember we did have problems with that charging some batteries. The other type used a thermal switch in the battery so it would switch off as soon as battery got hot. But in both cases the main problem was people would pop the radio in charger while the radio was switched on. And we had always though the odd flat battery found where charger said it should be charged was due to that. However now I begin to wonder!

People will spend a 'lot' (relatively speaking) on a decent charger then put 'crap' in them...... and expect the crap to work as well as decent batteries?

Whilst the better chargers are designed to accommodate a wide(ish) range of battery specifications there must be 'some' that are simply outside the range of acceptability?

Also, if you don't treat the batteries according to the manufacturers instructions (i.e. let them get completely dud, reverse polarity, over-discharge, over-charge, use in matched pairs - or threes or fours or whatever....) etc them you are just increasing the chances that the batteries will exhibit some form of problem.

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This post may contain nuts

I would agree that I have some old and low quality cells and the charger does seem to cope with most. Measuring I find it needs about 1 volt left in the cell with no load for it to recharge. It's not the cells which are at fault but the equipment using them. High power equipment is not a problem. Items like my flash gun cease to function well before the cell becomes too discharged to auto recharge. But low power equipment like my keyboard will over discharge the cells.
But the question is with a cell discharged so it shows only 0.5 volts on my digital meter which draws very little current being akin to the old valve voltmeter normally when put in a delta voltage charger considered to discharged to auto recharge.