Here's an update on the Electrified Miata. Preparation was the active phrase describing this week's activities. I ordered the coupling in preparation to join the Leaf motor with a Miata transmission. I now have the BMS boards in preparation for monitoring and charging. I worked on tuning PID for preparation for shifting without a clutch. I drained the Miata gas tank in preparation for removal. I bet you're getting the picture. There wasn't a lot of progress in any one area, but I'll give some highlights of this week's experiences in making an Electrified Miata.
The preparation for gas tank removal will require draining the fuel. I thought to myself that this newer (1999) car has an electric fuel pump and so I should be able to activate the pump and not deal with a siphon. Do you know how absolutely awful gas tastes? It looks like Mazda planned for an event like this by providing a diagnostic port. In this age of YouTube and car manuals, someone figured out that shorting two pins on the port, the fuel pump will run when you turn the key on so you could test fuel pressure, test the system for leaks, or drain the tank. I hooked up some extra fuel line between the Miata and my truck.
I went to ask my wife for a metal paper clip so I could make that connection on the diagnostic port. Her eyebrows shot up when I told her what I had planned. I nervously turned the key on the Miata and listened intently for those special noises only a wife can make when fuel squirts in an uncontrolled fashion. Fuel flowed between the Miata and my truck. No special noises, only the purr of the fuel pump. The tank on my Miata is 12.7 gallons and the gauge read just under 1/2 full. I'm guessing the truck got about another 5.5 gallons of fuel before the Miata was empty. Fuel filter, fuel pump and fuel sender units were all working well. When it was over, my wife told me that was pretty cool. I had done something cool in my wife's eyes. My day was complete and I felt great about 'knowing something cool'.
The next day I met Joe and he gave me six BMS boards so I can start on the software to retrieve and store battery information. He also showed me how those Anderson PowerPole connectors worked. I hadn't figured out how the parts I had worked yet and was slightly embarrassed. Joe showed me that the little metal clip inside them was actually a spring for the contacts and before the contact was inserted would prevent the connectors from going together as they were meant. Whew!! That means I have the right parts and now, know how to assemble them. Thanks Joe.
I want to make a video showing how to tune PID, but as previously mentioned ran into some inconsistency in the attempt. Upon further investigation, I found some of the inconsistency was caused by problems in my code. Then I had to write a few more tools so problems like I just had would be easier to find. After all of that, I'm close to the root of the inconsistency problem. I'll wait till I have verification and will be able to report the facts next week. I'm sure after spending the weekend under the Miata removing the fuel tank, I'll be ready to do some work in the air conditioning.
In other news, I tested 300 more batteries. All showed within 4 millivolts of each other. I also ordered an electric coolant pump and placed an order for a coupler made in 4140 steel. We should receive the coupler at the beginning of July.
We've got a project that the team could use help with. This project would both lower the cost and speed things up. We'd like to have the Leaf charger charge our pack. I've seen examples of people using Leaf batteries and the Leaf BMS system. I've been able to use the Leaf motor and inverter. I haven't seen anybody successfully re-use the charger yet and I have searched. If anyone is interested, and can work with CAN and 350 volts DC, please contact me.
To make more room in the shop, we'll be selling the go-kart. Let me know if you are interested and I'll get you the details. Batteries and head-light will not be included.
Next weeks goals are to remove the gas tank (and re-assemble the car so Teresa's car can go back in the garage), plan for where the batteries will go and finish PID testing and tuning.
Thanks for reading!