It is amazing how much difference a few volts make. That tiny little LiPo pack really helped my understand what extra volts would mean for my bike.
The main thing I noticed is the available power. Not too surprising really, since I usually cruise at 40kph using WOT as my "cruise control".
With the extra volts, at 40 kph I now have about 300w reserve power. So rather than slowly settling towards 40kph, I race towards it.
It really changes the whole feeling of the bike, especially with the new DH frame. It felt less like a push bike, and more like a motor bike.
To me this is about the tipping point for what is a "pedal assist bike", and what is a "why pedal type bike".
This graph probably highlights the change in performance the best. It shows the output power for the motor at various voltages 48, 60 & 72 (solid lines), as well as the power required to go up various grades of hill. 1%, 5%, 10% & 15% (dotted lines)
For example if you look at where the 1% curve intersects all the power curves, this tells you the typical WOT cruise speed on the flat
48V = ~40kph
60V = ~48kph
72V = ~56kph
If you do the same for a 10% curve, it tells you how fast you can climb a decent hill
48V = 22kph
60V = 32kph
72V = 36kph
Or look at a particular speed, 40kph, and see what sort of grade you can maintain 40kph
48V = 1% grade
60V = 5%
72V = 8%
So at 60V and a bit of peddling I could basically maintain 40kph for my whole commute. Rather than drop down to 30kph on the hills like I currently do.
Sooooooo. The question is: What will it take?
Let's see. Based on http://www.bmsbattery.com
US$66 - 4 more headway cells
US$36 - 20cell, 40amp BMS
US$35 - 240W charge
r (times two)
Total $172 + shipping
But hell if I am doing that, I might as well go for 72V.
$5 extra for the BMS, $66 for batteries.
So $242 + shipping
Just need to repackage things a bit on the bike to fit it all.