After looking at that site and what pertained to me, I think I'm to understand that there is no certain way to determine if my batteries need replacing, aside from inability to sustain a charge or separation of the cells (which may or may not be visible from the outside)? I think I also understand that replacing your batteries once every 52 weeks or so is proper maintenance? Wow, I've had mine for 4 years, never properly stored them and still don't notice any degredation! Better get some new ones before my luck runs out!