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