maha c401fs didn't reject alkaline AAA cells

This charger has always rejected NiMH AA and AAA that have high internal resistance. (flashes LED status light red)

Last week I accidentally (it was darkish and I mixed up nearly indentical looking cells) put in three energizer AAA alkaline cells. The red light went on and stayed solid red indicating charging. Later in the day the indicator lights turned green indicating done.

Even later I took them out and I noted lots of leakage around all the cells. Ooooops.

I was surprised it didn't reject these alkaline cells, I thought one of the reasons the charger checks resistance and rejects cells was to prevent it from charging alkaline cells.

Occasionally, fresh and little used alkaline cells have a low enough internal resistance to pass the test. Maybe that is what happened in your case?

(Note that people sometimes complain the C9000 rejects too many cells that other chargers will accept. Yet I have still persuaded the C9000 to accept some alkaline cells. So it is very hard to tell the difference between an alkaline cell and a bad NiMH cell.)

I have the same Maha charger that will charge damaged Energizers without warning. If I use my RadioShack or Eneloop chargers they will not charge the cells.

Thanks for the inputs folks. I don't use the 401fs much any more except to charge approaching end of life NiMH that the C9000 won't accept. I still get much use with these near dead cells - they run my son's 3xAAA choo-choo trains for hours between charges and I'd rather not kill new cells that get run to below .8V before the train stops working.

I am not sure how these three alkalines got in rotation. I haven't bought them in years. I suspect they came from one of the three train engines - in that case they must have been near dead.

I have gotten alkalines to "charge" in other smart chargers at times too. The results are almost guaranteed to be messy. Some chargers the current pulsed on a cell to "check" it is enough to slowly charge an alkaline over a day or three but I don't recommend it at all for almost every time you end up with a mess either from the charging or using the cell in a device.

Your luck was better than mine as I made the same mistake a couple of years ago with my 401fs. The charger was ruined either by overheating or by the leakage shorting out components on the circuit board.