All set for inspection

Shield were made to prevent accidental touching of battery terminals and powered connectors. They were made from clear acryl sheets that were painted black on the bottom side. The shields also block some of the spashing water from reaching the battery terminals.

Also the motor controller assembly got an enclosure which was modified so that it can be opened by a single butterfly nut.

As everything works now I think its time to have the Corolla inspected to make it street legal as an electric car!

Updated main circuit diagram

Quite many changes were done to the initial circuit diagram along the way. The changes were governed by the idea of not needing to alter the original wiring. The circuit diagram shown above shows the current state of the Corolla eFX electrical connections. I am currently happy with it as everything seems to work well.

The biggest change to the original circuit diagram are the six parallel connected power MOSFETs that are located between the 12V battery negative terminal and the chassis. They were added to boost the discharge current capability of the PCM circuit from 20A up to about 100A. The gates of these MOSFETs are controlled by the same gate drive that controls the 12V battery pack PCM discharge MOSFETs. This way when the PCM notices an undervoltage situation the MOSFETs are turned off  protecting the lifepo4 cells from potential damage.

The other major change was the addition of the 72V to 12V isolated power supply. This change made it possible to use a common 12V relay to wake up the motor controller. It also provided an isolated 12V power supply to be used by the panel meters. The 72V to 12V isolated power supply chosen is actually a low cost plug type offline AC/DC power supply that needs only about 50Vdc to start up. Not all of them do, but many of them do start with a lot lower voltages than the typically rated voltage range of 96Vac...250Vac. Of course, if used with a lower than specified input voltage the output current can not be expected to reach rated values.

Electric brake booster mounted

The electric vacuum pump and the vacuum operated microswitch were mounted close to the vacuum brake booster. The pump was mounted using a rubbery tube clamp to damp some of the pump's vibrations. This electric vacuum pump is quite a shaker when it is on.

12V PCM tested

After successful tests with the 72V battery pack's PCM branded as Signalab, I was expecting similar behaviour from the 12V battery pack PCM. I do not know the manufacturer of this board which is shown in the picture, but it is still available in eBay.

When I first connected the batteries to the 12V PCM I had my multimeter connected to measure the resistance between the P- and B- terminals. I was expecting the resistance to drop close to zero when the last cell was connected. To my disappointment the resistance dropped before the last cell was connected to the B+ terminated. My first assumption was that the board was faulty. A new PCM board would take weeks to arrive so I though that I would examine this one a bit more before giving up with it.

I disconnected the PCM and took it to my lab room to examine it with a laboratory power supply. I found out that the PCM worked as it should with the cell over- and under voltages, but what was left undocumented is that if any cell voltage would be less than about 0,7V the under voltage situation is no longer detected and the P- terminal is enabled again (if the other cell's do have a valid voltage between 2.0 to 3.85V). This happened to me during the first test of the PCM when the last cell was disconnected and still the P- was enabled.

Now that I know how this circuit works I decided to install it anyway although the circuit can not be expected to disconnect the load if for example a wire gets disconnected between the PCM and the battery pack.