Battery Management

This project has been a lot of research, installation, testing, refining, then reinstallation. Many people converting a car to an EV (or any project, for that matter) follow a master plan from the very beginning so that they only have to do each process one time. It’s a very smart strategy. My way always seems to be more of a creative process. It was no different when I produced music. I would see a song or an album completely finished in my head. But I loved the creative process along the way, trying various things and pivoting on occasion. The finished project was still very close to the concept, but the process was more like a vacation than following a diagram. For the car, I really wanted to test, enjoy and refine each major system before moving on to others.

This method has taken longer, but there has been a lot of fun along the way. For instance, we got to drive the car around the neighborhood with no interior, windows and only most of a floor. Only when we were happy with that we moved to the ignition and startup refinements. Then the gear shift, etc. This has resulted in many iterations of our wiring, but I have really enjoyed the process.

MANAGE THOSE BATTERIES

That brings us to Battery Management. A solid battery management system (BMS) is critical for any EV. When you drive your Tesla, Leaf, Bolt, or any other EV you don’t think anything about BMS. But you have probably heard the stories of EV batteries exploding. This is almost always caused by a lack (or failure) of battery management.

The simple explanation of a BMS is that it constantly measures the voltage, resistance and temperature of each cell (technically a group of battery cells, and my car has 84 of these “cells”). It uses these readings to control how much (if any) charge we should give the battery, or how much (if any) power we should pull from the battery. It can shut down the charger or the Tesla motor from taking or adding current. It keeps the cells balanced (so that they are all very close to the same voltage) and more. There is a lot more to it, but for this blog, this gives you the idea.

In case you are wondering, “Then how have you been charging your car without this very critical system?” Great question. I purchased a small trickle charger (the slower you charge, the safer things are) and would run it on a timer so that it would only charge for 6 hours at a time. I would monitor the volts and only charge to a maximum of 320V, which is about 60% of my maximum charge. I would also never charge with it unattended.

BEFORE WE TEAR THIS THING APART…

Before we tear down the car for this major work let us enjoy a quick November morning drive through the neighborhood…

We will be installing the Orion BMS2 in the coupe. After much research we felt like this is one fantastic unit. The support has proven to be second-to-none as well. This is a great product built by a great team.

In order for the BMS to read each cell, we have to install sensor wires to the PC boards of each Tesla module. This means the batteries come out. We are able to remove our battery box and open it up in under an hour:

The Orion BMS is a fantastic unit which comes in various sizes to handle large and small battery configurations. This is as close as I’ve ever been to wanting to endorse anything.

Inside our main box are twelve Tesla Model S modules (there is one hidden on the very top). There are two more modules in the trunk for a total of fourteen.

The box is so tight with so little room, it was tough to make this wiring very pretty. But it is all secure and does the job well.

After all the wiring was done we reinstall the box. Notice the whips exiting the box, which plug into the BMS in the footwell of the cabin.

Brett has always gotten into his work. We needed to create new paths for our sensor wiring.

Once everything was put back together I could finally read the granular details of the battery cells. All those little 3.9 volts add up to the 333.5 volts you see above.

After all that work I get to once again enjoy the car. I started by making a run up to the Los Angeles Porsche Experience Center to relieve a bit of 405 road rage.

Next up, installing my standardized J1772 charging port so that I can charge anywhere I go.

Cheers,

Paul