I'm with you PowerMe: two batteries ftw.
My Optibike Pioneer Allroad has two separate battery strength readouts: one is in the King LCD display on the dashboard and the second one is directly on the Battery. And for my money they're both wrong.
I fix Macs for a living and went to night school in electronics (a lifetime ago) so I know a thing or two about such matters, but the only way to learn a battery's behavior and performance is to spend time using it.
For example the bar-graph on the King Meter sags down to one bar on my commute back home from work. Then when I start pedaling above the motor's cutoff speed (and stop draining the battery) the display often jumps us to four (out of five) bars. Neither one is right.
But I have noticed that the bike will sink over 500 watts of current at the top of the battery's charge (riding in to work) and only makes the mid-400s (riding home from work. I think it's good for 25 miles but when I've gone 20, it feels pretty tuckered out
I could resolve this (non)issue by charging up at work; I do have a second charger there. Or, if I ever do a trip on the fat side of 20 miles, I could bring along my second, fully-charged battery.
That said, I have almost 1,000 miles on this whip and I'm still not really certain about the battery's personality. (Course I'm a little fuzzy about my own personality too, and I've got way over 1,000 miles on me.)
Allen