Hi all,
I had problems with rechargeable AA cells not fitting into battery holders. After close inspection, I found out the following:
IEC and ANSI standards specify a cell diameter of 13.5 to 14.5 mm for AA.
See
http://data.energizer.com/PDFs/E91.pdfSome rechargeable cells, especially the ones with the highest capacity, are at the upper limit of this diameter to get maximum capacity, and the outer shell is also thinner (= more volume for active material).
This means that pressure in the cell will expand the cell in diameter, which can lead to a stuck cell. Cells expand when they get hot. It is also possible that they get distorted when they are dropped, so that they are more oval than round. There is also the possibility that the shrink wrap around the cell has thickness tolerances beyond 14.5mm.
In my case, its a LED flashlight that is finicky about cell diameter. There is a sticker inside the battery tube that reduces the internal diameter to just below 14.5mm, so I have a battery set assigned to it that fits without problems. Maybe the designer was not aware of the extra safety sticker...
The alkaline AAs I had on hand (Duracell and some noname brands) all measure to about 14-14.2mm diameter.
My MixPre D accepts Kodak AA rechargeables with a cell diameter of 14.4mm with enough sideplay so that even hot cells should slide out without problems.
My recommendation: If a cold cell is a tight fit or if you have to force it into the battery holder tube (like on the MixPre or many flashlights) - dont use it. Look for cells that give some sideplay - they get thicker when warm or when they age.
Greetings,
Rainer