Just a quick note. I got an early X-Byke claimed to be 6Ah in all of the press releases and original specs. When you look at the pack of batteries within the 'bottle' it says very clearly 4.8AhI don't think this is likely. The Cytronex battery is 4.5 Ah, the other bottle battery around is the larger li-ion one on the Powabyke X models, 6.5 Ah, though both are 36 volts.
A 12 Ah battery would be more like a torpedo than a bottle and be far too bulky and heavy for the bottle mounts.
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I got a spare battery too- that also says 4.8Ah on the label inside the 'bottle'.
Things may have changed, maybe not.