For me it's not critical because we can just continue without assist, but I just assumed the bars would work similar to a smartphone...if the variables are consistent, then the drain should be too. Over 30 miles the weight, speed, and for the most part grade, were pretty consistent...yet the bar segments were not.
The battery is advertised as having a 25 mile range and it surpassed that pulling more than twice the weight it is designed for so that is great, just have to settle that the display bars aren't accurate.