Hey Electrified Miata team, here's the latest update in the never ending quest to go faster, have fun, and be safe! For those of you following along, last week, we were going to program the kart controller, finish one battery pack, finish mounting and wiring the power control box, make the Pi portable using the mini-battery pack and write some software to control the power. That sounds like a lot of work and it was! The work started on Sunday when Bruce and I got together.
I delivered the headlight and we took a little time to program the controller. Luckily for us, the software for that 12 year old product still exists and worked on a modern laptop since it was designed for an older version of Windows. Thank you AllTrax. We raised the controller voltage to 90 volts, raised the minimum voltage to 60 volts and lowered the performance to 20% of the controllers maximum. The reason we set the performance to 20 percent is to save the battery because one pack is not designed to put out the full 450 amps this controller is capable of. Bruce took a screenshot of the controller settings and he noticed the throttle up/down rates were only set to what looks like 40% of their maximum.
How could this have happened to us, lol? You can be assured that the next time we alter the settings, (likely for adding another battery, or when we have updated information on how much the current the pack can safely put out), we'll change these settings to something more aggressive. The kart looked beautiful so it was time to get the battery finished!
The correct parts for the battery arrived on Tuesday, and it took me a day and 1/2 to finish assembly. Lucky for us, Dad donated some of his hardware he'd accumulated over the years, and had over 100 8/32 nuts for me to use. It took quite some time to double nut all the studs to drive them in the pack and then take them apart. Many thanks dad for the all the parts. I'm betting Dad didn't know he was saving things to make an electric car! Once the pack was finished, the next project was the power distribution box.
This box is intended for being re-used for the leaf motor, so I used some larger parts than what would be strictly needed for the go-kart, namely the fuse. The box accounted for another one and 1/2 days of work to puzzle out how the the components were going to fit and where all the wires go.
The larger 0/2 cables take more preparation time with heat shrink and the hydraulic crimper. After all that, we still needed some software to run it, but that effort was nearly trivial, compared with all the physical activities Finally, all was close to ready when we met.
Everyone had something to work on.
Ed worked on the power distribution box, drilling the final holes for the big wires going in and out. Bruce worked on assembling one more power cable and using the hydraulic crimper. Brian restored the throttle to its original location and operation, while I finished making connections between the kart, Pi, mini-pack and power distribution box. Joe had to supervise, as there are only so many hands that can fit on one kart without being in each others way. After all jobs were finished, we connected the batteries and tried to make it spin. Initially nothing happened and I thought we'd need to get the laptop interface to the motor inverter to find out what was wrong. It turned out the throttle needed one more adjustment. As soon as it started spinning, we started getting some drop outs, where the pi would reboot. Brian found one of the power leads to the mini pack was loose. After fixing that, we still had intermittent drop outs, but that's a problem for next week. Battery cell drop was about .1 volts when under load (using the brake and the throttle at the same time). Visible progress and another step in our quest for speed, fun and understanding.
Plans for this coming week are, documentation, mounting parts, re-routing wires, a plan for cell testing, having fun. Documentation and planning are extremely important to the project, so can all work together smoothly. I've been behind on this, so I'll be correcting that this week. Someone asked me if I was happy with this successful milestone. Happy, yes. No one got hurt, there are no major impediments to being able to drive kart, other than mounting everything and stabilizing our wiring connections. Satisfied, heck no. Twenty percent performance?? As long as I can dream up ways to go faster on a limited budget, I won't want to rest. I'm starting to miss my Pantera! Getting the kart to spin the wheels is one step on the journey of miles, but it all starts with just one step.