In order to improve and take full control of the battery on the Super Soco TC Max I'll try to build a new upgraded one. I think range can be improved around 25% by using 18650 cells. First thing to do is gather the parts and plan out how to arrange the 18650s. Some cell holders are obtained from AliExpress.
Cell Holders and Layout
Cell holders designed for 80 18650 cells are used. They form a 16 parallel, 5 series module. There will be four modules stacked and connected in series making up a 16 parallel, 20 series battery pack with 320 cells total. These holders cram the most cells in whilst maintaining an easy shape to work with. The holes between cells accept a 4mm fibreglass rod to stop the modules moving around.
BMS
In order to maintain the cells within set parameters a BMS must be used. The Ant BMS has plenty of useful features including bluetooth programming and data acquisition. The TC Max pulls around 70 amps peak so the 100 amp specification of this unit is fine.
An additional communication module allows the bike's original battery meter to work with the new pack.
Structure and Insulation
Once the small holes in the cell holders are drilled clear with a 4mm drill bit, fibreglass rods can be inserted. These help to maintain the structure of the battery and hold the PTFE separators in place.
1mm PTFE sheets are cut down to size and drilled to allow the fibreglass rods to pass through. PTFE has a high melting point so should remain intact even if high temperatures occur. It insulates the modules from each other to prevent short circuit.
Cells and Welding
320 LG MJ1 cells are assembled into modules. The LG cells are rated at 3500mAh and a maximum discharge current of 10A. The bike should pull just over 4A per cell, well within specification.
Two layers of 0.2mm pure nickel sheet are welded using a K-Weld welder. Extra tabs are left on the sides to allow the module series connections and BMS cell connections.
Connectors
Battery sockets matching the original TC Max plug are used to allow the new pack to connect directly to the bike's existing wiring without any modification.
BMS Display Screen
The BMS has built in bluetooth to allow programming and monitoring of cell voltages. To make it possible to check the pack and cell voltages without a phone, a screen is added to the battery. It displays total voltage, individual cell voltages and current both in and out of the battery.
Assembly
