Hello Electrified Miata fans! This week many of the longer term plans came together. I'm overwhelmed with lots of things to do, but that's a good problem to have. The coupler is here, the coupler is here. And, drum roll, IT FITS.. Whew. No grand celebration yet, but maybe a glass of Scotch. Wasn't sure if emachineshop.com would produce the part correctly or not. A coupler that fits means we can go forward with pulling the Miata motor. Removing the Miata motor means we need to borrow an engine puller. A Miata motor will also need a new home, as I won't need it. Okay Bill, enough of the future problems, settle down. What got done this week?
Last week's goals were to cut plastic to protect the batteries, work on the BMS software and evaluate the coupler. We met all of these goals and more! Let's talk about this week's accomplishments
I met Ed at his shop and we cut some plastic. I now have side plate protections and a place to mount the BMS boards.
The hole in the side cover is where we can access the bus bar bolts. A plastic cover from the plumbing section at Home Depot fills that hole once we are done connecting everything. Thanks Ed for your patience, expertise and providing a great shop to make more things. Ed has the main shop table cleared for mating the Leaf motor to the Mazda transmission. I know I'll need gear oil in the future for the transmission and guess what?
I was reading through the Austin Miata Facebook group when I came across FREE gear oil! I messaged Arm Suwarnaratana and arranged to pick it up. I *really* enjoyed meeting him and talking about our various projects. He has a nice blue Miata he road races. His Miata has both Ethernet and a Raspberry Pi too! I could have talked to him for hours. Thank you so much, Arm for your donation to the project! It helps a *lot* when working on a limited budget. Also on Facebook,
Noah Biebelhausen needed fuel injectors. I'm not going to need mine so I offered them for a small donation. Unfortunately, my used injectors didn't fix his problem, but we both thought it was better to spend $20 than $170 for some new ones. Thank you Noah Biebelhausen for your donation! I've already mentioned the coupler arrived and it fits. I let the Austin Miata Facebook group know the motor will be available. The motor sold fairly quickly. Thank you to all who bid on it. The Austin Miata group rocks and I am glad to have joined.
Joe, our BMS expert, a former Miata owner himself, has been making great progress on the BMS boards as well. I'm trying to persuade Joe to author an article so he can describe the journey making the BMS boards and everyone can get get to know him better. Joe and I decided to lower the speed on the communication between boards to 2400 baud to get around the signal degradation problem described in (link) this blog. With Joe's new test fixture, he can install the firmware
and verify a board's functionality in two minutes! This is a significant improvement when dealing with 100 boards. So far, he's found one bad board that had a poor connection with the on-board temperature probe. Thank you Joe for all your hard work! I couldn't do this without your help! The first batch of boards will be available to me next week, so look for updates on the go-kart and battery testing.
Having the BMS boards nearly here means I have to get the software ready. Working on software again is soothing to my soul. Even though the prototype version of the software is a little 'brute force' in places, it was fun to work on. Let me describe the problem the BMS software is solving. First and foremost, we have to keep everyone safe. The BMS helps achieve safety in two ways. One, it can be used to monitor battery cell temperatures, and two, it monitors battery voltages. Wen Murphy comes along and brings his problems, we need to describe where the problem is to the driver or mechanic. This means all the cells need labels. Somewhere, I have to associate the cell labels and the BMS board identification numbers. I'm sure a mechanic would rather see problem with "Pack #2, cell 3", rather than problem with BMS id 0x17CE66. To further complicate the issue, it's unknown if the operating system will always assign the same serial port name to each chain of BMS boards. So my part of the software has to 'figure out' which BMS boards are connected to which serial ports. The software then looks in a database to find the mechanic preferred name so if trouble occurs, the system can
display names that make sense. Enough about the BMS! How close are we to drive-able action?
Bruce has the go-kart again and will be providing mounts so the Miata battery packs can be bolted up to the go-kart. After the packs are mounted, we can work on the power control box mounting. After that, we'll have to mount the Pi's. Thanks Bruce for being able to take my vision and a complete lack of details and make it work! Everyone needs a brother like Bruce. I'm guessing in a few weeks, we'll be able to test the packs and BMS on our go-kart. We'll shoot some video when that happens.
Next weeks focus will be preparation for pulling the Miata motor, more BMS software so we can charge the Miata packs. Thanks for reading! Wishing everyone health and fun!