I just go by what I read on the web, for example:
http://www.batterystuff.com/blog/how...ry-is-bad.html
Observation with my own battery, I charged it for 12 hours with a basic model Ctek charger, fresh off charger it read 12.7V. I put a 10A load on it for 10 seconds, after which it read 12.4V. That is not right if battery is ok. It should not go down to 12.4V after a 10 second 10A load.
I charged it a second time for 14 hours using de-sulphation mode and the result was same as above.
Apparently lead-acid batteries are not supposed to spend a long time below 12.4V, mine has and has lost capacity.
http://www.tayna.co.uk/tutorials/car...ur-battery.php