Watt hours = 642.70
Ah hours = 13.27
These figures are very good considering the battery's about 18 months old. When it was new I tested it and got about 660 Wh. So the loss is only 2% or 3%.
That said, this battery (and the four others purchased at the same time: batteries #s 11 through 15) have a lot more voltage sag than batteries #s 1 through 10.
So, when the battery has used up about 40% of its energy the voltage sag is sufficient to cause the bike to stall out when accelerating from a standing start. To avoid stalling one must accelerate from a standing start very gingerly.
Odometer reading 10835 km
Update:
These batteries (#s 11 - 15) are poor performers when used singly but are very good when used in tandem.
When one battery is reduced to 60% of its charge it results in problems with stalling on full acceleration. Using two batteries in parallel gives us 200% of power. We can use 140% before we get down to the 60% of power before problems begin.
This means that the second battery can utilise 100% of its power. It gets even better when you use three batteries in parallel (which is what I use when I pull a trailer).