Here are some faults with batteries and cells that you may not be aware of.
Dry cells are called Leclanché cells after the name of the original inventor in1866.
Originally they consisted of a carbon rod and zinc rod or sheet in a solution of ammonium chloride in a glass jar, but if the jar was tipped over, the contents would spill.
To prevent spillage the cell was constructed with a zinc case and a carbon rod down the centre with black pitch or tar to cover the cell.
Because the cell did not spill, everyone thought it was "dry."  So the name stuck.
The cell also had  Manganese Dioxide depolariser and a number of other additives to prevent the zinc case being attacked when the cell was sitting around..
But basically all dry cells are constructed the same way.
By adding carbon to the depolariser, the cell will deliver a higher current but nothing can increase the capacity (amp-Hr of the cell).
These are called zinc-carbon cells, dry cells, or manganese cells. 
The only reason why some cells are poor performers is due to the thin zinc case, filler instead of manganese dioxide, little or no additives, such as carbon, or a thin mix of ammonium chloride.
Heavy Duty cells use Zinc Chloride instead of Ammonium Chloride as the electrolyte but the overall capacity is the same. The Zinc Chloride improves the current capability and the terminal voltage is slightly better over the life of the cell.
The next improvement was a cell called Alkaline. These cells have a capacity of about 2-4 times that of a "dry cell" and will deliver a higher current - about 2x-3x higher.
There are lots of other types of cells on the market such as button cells, air depolarized cells but the first two we mentioned, are the most popular.
However they can have some very unusual faults and this is the issue we are describing.

Most "dry cells" are enclosed in a steel jacket because the zinc case gets eaten away when the battery delivers a current and eventually a hole is produced. Secondly, the cell produces water as a by-product of producing electricity and the insides can become quite "wet." This is the fluid that leaks out.

1. Some "dry cells" have a very poor jacket of cardboard and they leak ammonium chloride liquid. This liquid is conductive and will attack copper. Avoid these cells.
2. The terminal voltage drops very quickly with some dry cells to 1.1v, even though they still deliver a high current. The cause is unknown. Avoid these cells.  Other cells will maintain 1.55v, right up to the end of their life. These cells are fantastic.
3. Some Alkaline cells go "open circuit" for no reason or produce 0v output for no reason.
This also includes the 9v alkaline batteries.  Alkaline cells can be very unreliable for this reason, so don't use them for emergency applications. 

If you have any other interesting faults, let me know.

Colin Mitchell