Normally the self test is not a full 3 hour run down, rather the NiMH runs it down for about 30 mins, and verifies that the cell voltage drop is 'on track' not to fail in the declared time. The larger lead acid units are tested by verifying internal impedance from a very short high current discharge - a higher than expected voltage droop indicates loss of useful plate area, and reduced capacity, While both methods are a bit approxmate, usually it is pretty good, within about 10% of a proper capacity test.
It is more important in such cases to re-fit the right sort of replacement battery, as a change of chemistry, or the use of a gel lead acid instead of liquid filled a glass fibre mat can confuse the self test, either into warning when it should not, or worse, not warning when it should.
Normally the self test is not a full 3 hour run down, rather the NiMH runs it down for about 30 mins, and verifies that the cell voltage drop is 'on track' not to fail in the declared time. The larger lead acid units are tested by verifying internal impedance from a very short high current discharge - a higher than expected voltage droop indicates loss of useful plate area, and reduced capacity, While both methods are a bit approxmate, usually it is pretty good, within about 10% of a proper capacity test.
It is more important in such cases to re-fit the right sort of replacement battery, as a change of chemistry, or the use of a gel lead acid instead of liquid filled a glass fibre mat can confuse the self test, either into warning when it should not, or worse, not warning when it should.
