1 Mar ME1003 DC Brushed Motor
1 1967 Volkswagon Sandrail
1 Alltrax SPM-72400 Motor Controller
1 Motor to Transmission Adaptor Plate
1 Cycle Analyst Computer
1 600A shunt
150 5Amp-hour LiCoCO2 LIPO Cells (3kWh)
1 Aluminum Military Footlocker
1 800W Charger
1 12V Cooling Fan
6 6S LIPO Balancers
2 Buckets of Sweat
About the build:
After finishing the Tri-Fly build in 72 hours and proving the power capability of these LIPO batteries I use on my quadcopters, my friends and I were convinced the ME-1003 Montenergy Motor and the Hobby R/C LIPOs would suffice for a light weight electric vehicle. My friend Justin was able to find a Volkswagen Dune Buggy to use for the build – anything heavier would require a different motor and more. This build is simple, most of the challenges are in the mechanical sense, “How do you mate the motor to the transmission?”, “Why do the drum brakes not work well?”, etc. This is a learning experience in antique vehicle maintenance/repair and high power electrical systems.
The first problem to solve was mounting the motor to the transmission. The motor has a circular shaft with a key, while the transmission has a spline shaft. A couple was needed, as well as an adapter plate for mounting the motor to the transmission. After doing some research it was apparent the best couple to use wass a clutch-less couple. Clutch-less meant harder to shift in an emergency scenario, but with normal driving conditions and the fact an electric motor can easily speed up and slow down, it should shift just fine and without issue. Another major reason for this couple type, is in case the shafts are slightly misaligned, any extra movement will be taken care of by the couple rather than by flexing shafts or slowly ruining bearings.
While the vehicle was being looked over, brought up to road standards, and the motor mounted, the battery pack was also underway. Having learned how about the battery capabilities with testing on the Tri-Fly, working on a larger battery would be required to achieve usable driving distances on this buggy. Looking at the old battery pack, it was apparent learned how badly the design was, it was scary working with high currents and 96 volts when the wiring wasn’t easy to glance at – at one point I shorted a battery to another battery causing sparks and instant cell death – this could not happen again! Look at the old pack:
It’s a mess, I know. A new connection method was needed to continue. So began the tedious process of making 300 new connections. Soldering and heat shrinking so many was no simple task, and took many nights after work. The results were beautiful:
Then the enclosure was needed, as well as a way to secure the batteries while driving like a possible maniac. This was done by creating a wooden box to fit within the used military aluminum footlocker. In between the two layers, some fire-resistant insulation was added, just in case. Velcro was added to the battery half, to help secure them, in retrospect this stuff was almost too strong!
Finally the batteries were fitted, connections made, and balancing units added between the sets of 6 batteries that each made up 96 volts. The battery sets were connected to an aluminum bus bar by o-ring connectors to holes that were drilled and tapped. It was a lot more work than it looks like! In the end, There was a trunk full of batteries that could easily power a modest house for an afternoon.
Finally, it seemed to be getting somewhere. I spent an afternoon with Justin trying to figure out why the hall effect sensor based pedal wouldn’t read properly on the motor controller. After busting out the scope, looking at the output from the pedal it was immediately obvious: there was noise in the line, it was guessed to be from the cheap Chinese 5 volt regulator picked up from Ebay. After adding some large capacitors to the input of the regulator, it was stabilized!
One problem down, many more to go. The motor was a little undersized for the motor controller, and overheating was a real possibility that would be hard to diagnose while driving. After reading how some people online were using this motor in their drag racing electric motorcycles, with a fan cooler, it was decided a fan cooling system was a good safety to add. Being an electric vehicle, every bit of current used would subtract from my mileage capabilities. To combat this issue, Justin added an IR and temperature controlled relay that would turn on the fan based on preset temperature readings from the motor. To test this setup safely at home rather than on the road, we hooked up a soldering iron to the temperature sensor, the relay, and then the fan. It seemed work good enough for this job. Then I used an old project box I had laying around from when I built high power lasers, to house the electronics safe from the elements.
To be road safe, this vehicle needed headlights, to conserve energy yet again LED headlights were the weapon of choice. Luckily these are readily available these days. To save time and money, the headlights were bought complete, and a current controlled LED driver was bought as well. As you can see, it works quite well!
Finally, months after the beginning, it was discovered the drum brakes were bad, and certain parts needed repair. While the vehicle was dismantled for brake work, we decided to add some jazz! Sparkling metallic blue paint was the choice, no point in going red, A pop-up paint booth was setup at the local hacker space, a base coat was added, followed by the metallic blue glorious you see here:
A lot of mundane work, and back of the napkin math was left out of this log, but if anyone has any questions, feel free to email me, firstname.lastname@example.org and I’ll divulge just how awesome the torque monster is, as well as any details you might wish to know. Thanks for reading!