⚡peed boost

 A mighty new 48 V battery (13S4P Super Shark from EM3ev) has been powering the Firefly for the past 150 800 km.  Voltage means speed, and this leaves the 36 V original in the dust.  It's worth mentioning that 13 series cells exceed the motor controller spec, but an internet post said it was ok.
😉

 

The hole-pattern gods must have been smiling on me, because the new battery mounting rail fits the existing bolt holes exactly.  I did add a pair of large c-washers behind the rail, to distribute load onto the plastic part.

Frame mounting holes and back of battery rail.
The small washers are unused.

One of two c-washers between frame and plastic.  Without them, the raised metal rectangles at the bolt holes (prev. picture) would probably crush the small overlapping areas of plastic (less than 1 mm wide).

Aside from a galloping speed and oodles of range (about 70 60 km), the battery broadcasts more status information than most people care to know.  In a nod toward reason, I spliced four series diodes into the charge cable, limiting the Voltage to 52 V (80 % charge).  The Super Shark's higher mass and speed cause extra mechanical stress - inspect regularly!  More weight on the front wheel does help traction.

BMS Monitor shows battery status and cell voltages (via Bluetooth).  The BMS circuit prevents unsafe voltage, current (?) and temperature, and shuffles charge between cells to equalize their voltage.

6437 km (4000 miles)

A quick update since it's been nearly a year: The last crash took some wind out of my sails, and the MS that put me in the chair keeps progressing, but the past 1400 km have been fairly uneventful with the rubber side staying down.

• The Q-211 front tire finally gave out with a slow flat and cords showing.  Lifetime: 3629 km
• The larger 36 V, 11.6 Ah battery started cutting out, perhaps due to unbalanced cells, so I reverted back to the original 6.6 Ah one.  Lifetime:  5050 km (about 250 cycles assuming 50% depletion)

Screenshot from the VESC phone app (Android).  The electronic FREEwheel is active to improve coasting and reduce torque chatter.  The throttle holder is keeping MAXimum forwards throttle until I press reverse.

Replacement Q-211 tire before mounting.