Scaled down Miata?

​Hello Electrified Miata Fans and Happy New Year!  This week's focus was getting the go-kart running.   Wait, go-kart? What happened to the Miata? We need to test and verify our current revision of the BMS boards before we commit to the next revision that will be used in the eMiata. The final part of the BMS that has not been 'field tested' is the charging cycle.   To charge, we first need to discharge.   The handiest place to discharge batteries is the electric go-kart.  Have you ever seen a go-kart with a BMS system and wireless interface so it can be controlled by the web browser on your phone? Neither have I.  Please join us as we test our systems on the go-kart.

The wireless interface is one of the remaining unknowns in our system using a Raspberry Pi.   Having a wireless web interface  will allow use of common devices like our phones or a tablet for a display. There were instructions on the internet so I was
pretty sure it was possible, but details do matter.   We use a metal case on our Pi's so I was curious as the strength of the Pi's wireless signal as metal blocks wireless signals.   Would it work at all?  Let's find out!

I am 30 years comfortable with Linux, so I started executing the steps to make one of the Pi's behave as wireless access point. After the install, I couldn't detect a wireless signal.  Rats.  The first internet set of instructions I found didn't seem to work.   The neat thing about Linux is there are usually multiple ways of accomplishing a task. Since the first way didn't work, I tried another. Unfortunately, during installation I managed to remove my ability to connect to the internet and it was easier to start with a fresh system on the Pi. After using the second method of enabling a Pi to use wireless, I had a detectable  network signal which was plenty strong!  Yay!   However, I couldn't make our web application work.  Frown.  When I did the fresh install, I unknowingly upgraded my version of socket-io, and I now needed an updated JavaScript package. After some research, trial and error, we have a working system that can serve our web-page wirelessly!   During the trial and error stage, I was reminded that our test user interface code depends on a connection to the internet. This was a decision of convenience 9 months ago.  We'd always know there would be a time to install those resources on the Pi.  That time has arrived! 

The Pi's and all the supporting electronics have to ride along on the go-kart.  As we discovered from our previous experiences on the go-kart,  all manner of road debris seem to get into the electronics.  Having a enclosed box would be good, :) Now we need boxes, connectors and connecting cables.   Dave Evans made the box to support the Pi's while I worked on the mini-pack battery box.

​Brian and Bruce came over for car night and they assembled the custom fit Ethernet cables for the three Pi's.   They also made the power cables for the batteries.  I learned that an angle grinder with a cut-off wheel works great for cutting thick 00 power cables!  I tested and  adjusted one of the voltage regulators to produce 9 volts that the network switch needs.   Lots of holes drilled and connectors installed.   Now all wires need to be soldered and connected. Should I document the wiring?  Nah, the go-kart will only be in use for a few charging cycles and then most of the pieces will be re-used in the eMaita.   For anyone who knows me, you'll recognize the Bill-speak. Documentation?  Maybe someday. ;)

While I'm sure the go-kart is of interest (isn't that what a Miata is?), what about the actual car?

Bruce and Eric have installed and painted the motor mounts, the bell-housing adapter, and the front battery tray. They also constructed a mount point for the electric water pump. Currently, they are fixing a problem on the rear end.  Here's why.

When I first dropped the rear end to remove the fuel tank, one of the brace bolts snapped off.   Bruce welded an extension to the leftover bolt and was able to remove it.  He found someone had cross threaded the bolt.   Thanks to Ed, we had a metric tap available and Bruce and Eric were able to fix the threads. While having the rear end out, hopefully for the last time, they discovered the driver's side brake caliper had be leaking as evidenced by complete paint removal from the lower a-arm. I'll be looking for a new drivers side rear caliper. Yes, Bruce and Eric have been quite productive and busy during the holiday break!  Thank you so much!

Next weeks goals will be to get the go-kart running so we can test the
BMS boards.  The problems that need to be solved for this to happen are:

1.  Remove the dependency on the internet from our JavaScript code and
    install those resources on the Pi.
2.  Oodles of wiring and soldering and testing each piece along the way.
      The contactors had better work properly and in the right sequence
       before being tested  with  440 amps connected.
3.  Programming the go-kart motor controller to use the correct voltage
      and power for these eMiata battery packs.
    
As always, thanks for reading!