The NiCad service
guys have advised the following:
When the battery
first comes into the shop, it is physically checked for defects and capacity tested (at a 1 or 2 hour rate). If it passes, it is recharged and returned to service.
If it fails the capacity test (for whatever reason), it is discharged completely to the extent that when the cell voltage drops below 0.5 V, shorting clips are attached across each cell and left in place for 12 to 24 hours. It is then recharged (usually over 1 to 4 hours) and capacity tested again. It may require 3 such cycles to bring the battery
back to specs.
If three cycles fail to bring it back, then the offending cell (or cells) is (are) replaced. If there are 5 or more crook cells (in a 24V battery), then all cells are replaced.
Of course the temperature sensors are also checked during the service along with a lot of other parameters (electrolyte levels, individual cell voltages at 15 minute intervals, etc).
Capacity tests are carried out at intervals anywhere between 1 month and 24 months (depending on manufacturer and operator requirements).
There are minor variations in the procedure depending on the manufacturer’s individual maintenance manuals
Hope this helps.