If you know a lead acid battery will be used to maintain a very small load for a long time, there are changes to the construction that will aid this - internal resistance is less serious than it would be for one required to provide short high level pulses, and so wider electrode spacings and less concentrated acid slow the ageing process, but only to a small extent, perhaps a factor of two. AGM and gell cells are less likely to dry out than a traditional wet cell, and for very lox current applications, drying out is the failure mode.

In the other corner, an engine cranking battery has poor self discharge, but is very low internal resistance. I' expect to check the state and perhaps top up charge every few months  if unloaded. 

Calcium may be added to the plates in place of the 5-10% antimony that is used to make the lead plates stiff, to make  long life batteries,  and traces of silver or tin may also be added.

Exact alloys are the battery maker's trade secrets.

You will not get the full thousand cycles of charge and discharge if you only cycle it once a year, and if you only need a few cycles in the full life use, it soon becomes worth looking at other battery chemistry options, and even primary cells instead.

Mike.

If you know a lead acid battery will be used to maintain a very small load for a long time, there are changes to the construction that will aid this - internal resistance is less serious than it would be for one required to provide short high level pulses, and so wider electrode spacings and less concentrated acid slow the ageing process, but only to a small extent, perhaps a factor of two. AGM and gell cells are less likely to dry out than a traditional wet cell, and for very lox current applications, drying out is the failure mode.

In the other corner, an engine cranking battery has poor self discharge, but is very low internal resistance. I' expect to check the state and perhaps top up charge every few months  if unloaded. 

Calcium may be added to the plates in place of the 5-10% antimony that is used to make the lead plates stiff, to make  long life batteries,  and traces of silver or tin may also be added.

Exact alloys are the battery maker's trade secrets.

You will not get the full thousand cycles of charge and discharge if you only cycle it once a year, and if you only need a few cycles in the full life use, it soon becomes worth looking at other battery chemistry options, and even primary cells instead.

Mike.