Shelf life and sell by date/best before date
Primary batteries are provided with a sell-by-date or best-before date. They should be suitable for normal use until then, so the overall performance should be up to par.
Performance can be split into capacity and safety. Capacity will decrease slightly over the years but safety has to remain a 100%.
In order to measure these one needs a lot of time; shelf life these days is up to 6 years, but itís not practical to wait so long for a result.
That is why accelerated aging simulations are used. Batteries are put to a so called stress test: high temperature or frequent major temperature change for a longer period of time.
After this stress test a selection of the normal IEC-tests are executed. These results will be compared to the standard outcome.
Results in safety should be the same. Decrease in capacity (medium and heavy duty application tests) will give an indication of shelf life,
If all product details are required additional tests can be done at the end of the real shelf life.