My latest DIY build is an extra long-range cruiser based on La Croix deck and enclosure and MBS trucks and wheels. This is part of five of these boards in a group DIY in Perth Australia.
Basic details and major components of build are:
- La Croix deck and carbon fibre enclosure link
- MBS Matrix II Pro Trucks link with MBS Rock Star hubs link and 200mm Roadie tyres link
- Flipsky DUAL FSESC 6.6 link
- Samsung 21700 51E cells link 5Ah each in 10S 6P configuration to give 30Ah pack) 5Ah each in 10S 6P configuration to give 30Ah pack
- 2 x Maytech 6374 170KV 65A FLC 3.5kW sensored and with motor temp link
- Custom made Aluminium Motor mounts with cross-struts (from @Idea)
- 72T Aluminium wheel hubs (from @Idea) and 18T motor gear link with 20mm belts link
- Metr Pro module https://metr.at/shopfor telemetry and vesc interfacing (with antenna due to carbon fibre enclosure)
- Charging circuit designed for 20A but intend to normally charge board at 10A maximum (divided by 6 cells = 1.7A each = 0.34C – so conservative)
- External DieBieMS BMS https://www.electric-skateboard.builders/t/diy-6s-to-12s-bms-with-can-diebiems/2639 for charging only (build includes a new external BMS charging box housing the DieBieMS BMS )
- Relay based board main switch (no failing anti-spark switches for me)
- On board headlights powered from main battery pack
- Rear Brake lights triggered from remote PPM signal passing below 50%
Basic design parameters considered were:
Board Speed – based on 90% vesc and overall mech/electrical efficiency, 4:1 gear ratio, 200mm wheels, total board mass of 93kg, no head wind and level path, 0.9 sq m frontal area, smooth asphalt path , steady state conditions – the max speed at 95% duty cycle is as below. The gearing and motor KV was selected to give minimum 40km/hr board speed over all battery voltages.
Range/Battery Pack – desire on this build was to maximise range by installing maximum battery Ah in the La Croix enclosure compartments. After a bit of searching – settled on a brand new 21700 cell from Samsung 1NR21700 50E with basic specs -5Ah 10A continuous discharge capacity and 15A intermittent discharge capacity. Decided to go for 60 of these cells in 10S 6P which gives approx. 1,080Wh with 60A continuous discharge capacity.
Based on my current DIY board average consumption on Evolve pneumatics ATs of 13 Wh/km (average over approx. 1,500 km of rides over past 6 months) this gives a calculated range of 83km.
After looking at the La Croix enclosure battery compartments – determined that the compartment width was approx. 240mm - which would fit very nicely 11 x 21700 cells but not 12 (short by about 20mm). But decided to order the 60 Samsung 1NR21700 50E cells and have a play with a few options to see how they could be fitted with a fall-back position to go with 10S 5P or maybe 12S 5P with two parallel packs in rear compartment.
Motor and motor mounts - Decided to go with sealed Maytech 6374 motors with @Idea mount V7.3 with cross struts but without idlers. My current board (with 175mm AT tyres) has a pair of Racestar 5065 200 KV motors rated at 1,650 W with a pair of FocBoxes and this has plenty of power and acceleration torque – so the Maytechs 3.5kW motors are a bit of an overkill – but they should run very cool and efficiently.
All the major material and equipment was ordered during Nov 2018 including the lots of misc. stuff for building boards such as nickel strip (10mm x 0.15mm), 12 awg silicon wire, 14 awg silicon wire, 22 awg silicon wire, pack heat shrink, fish paper insulation, neoprene foam sheet, bullet connectors, switches, charge sockets, headlights, etc.
Boards rocked up from Canada last week - thanks Alex
and cells rocked up from nkon and motors from Maytech ( about 4 week delivery for both)
so now the build starts