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I also wonder how much is lost over time from natural self discharge, it may be small but it should be public information.
It is, every battery manufacturer has tons of 'technical data' on what they make and it's important that the charger be designed for that SPECIFIC battery. For my remote energy control systems ,3 decades ago, I spent months pouring over data, then decided on a Gates SLA battery, same as used by the USA Nuke Subs. Designed /built charger to THEIR specs and gee whiz the batteries performed even BETTER than what was published !
BTW self discharge can only done with the battery totally disconnected from the 'product' and the 'charger'. One reason car batteries die is that even though the key is off, car not used, several computers are still active, radio,alarm system,etc.