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Mitsubishi Miev Battery Pack

By Nikolay Shishkov • July 03, 2018

EV95lev-50mievrav4 ev

I have aquired a battery pack from a crashed Mitsubishi Miev produced 2017.

I am planning to use the modules in an old Toyota RAV4 EV produced 1997 with NiMH battery that is no longer produced.

The LEV50-8 modules from the miev battery pack are suspiciosly exactly the same size as the EV95 NiMH modules used in the RAV4 EV.

Part of the project is to interface the new pack with the old car, and to be able to do that I had to reverse engineer the communication protocol in the RAV4 EV and the one in the Miev.

The Miev pack has a CMU (cell monitoring units) on each module and a BMU (battery monitoring unit) that communicates with the CMUs on a separate CAN bus. The BMU communicates with the rest of the car on an external CAN bus.

On an earlier versions of the Miev the BMU lives under the rear seat of the car. In this 2017 pack the BMU can be found in the middle of the pack.

The messages on the internal bus are with CAN ids 0x6X1, 0x6X2, 0x6X3, 0x6X4 sent from each of the CMUs, where X is the number of the module - from 0 to C. There is also a 0x3C3 message sent from the BMU that contains information / command about balancing.

Here is a relevant but untested Arduino code for decoding the CAN bus frames from the CMUs:

_lev_typeId = rxId & 0x00F; // 4 messages per CMU 1, 2, 3, 4
    _lev_CMUId = ((rxId & 0x0F0) >> 4) - 1; // CMU id

switch (_lev_typeId)
    {
      case 0x1:
      _levMod[_lev_CMUId].temp[0] = canMsg[2];    // temp1 + 50
      _levMod[_lev_CMUId].temp[1] = canMsg[3];    // temp2 + 50
      _levMod[_lev_CMUId].volt[0] = canMsg[4] * 256 + canMsg[5]; // volt 1
      _levMod[_lev_CMUId].volt[1] = canMsg[6] * 256 + canMsg[7]; // volt 2
      break;

case 0x2:
      _levMod[_lev_CMUId].temp[2] = canMsg[1];    // temp1 + 50
      _levMod[_lev_CMUId].temp[3] = canMsg[2];    // temp2 + 50
      _levMod[_lev_CMUId].volt[2] = canMsg[4] * 256 + canMsg[5]; // volt 1
      _levMod[_lev_CMUId].volt[3] = canMsg[6] * 256 + canMsg[7]; // volt 2
      break;

case 0x3:
      _levMod[_lev_CMUId].temp[4] = canMsg[1];    // temp1 + 50
      _levMod[_lev_CMUId].temp[5] = canMsg[2];    // temp2 + 50
      _levMod[_lev_CMUId].volt[4] = canMsg[4] * 256 + canMsg[5]; // volt 1
      _levMod[_lev_CMUId].volt[5] = canMsg[6] * 256 + canMsg[7]; // volt 2
      break;

case 0x4:
      _levMod[_lev_CMUId].volt[6] = canMsg[4] * 256 + canMsg[5]; // volt 1
      _levMod[_lev_CMUId].volt[7] = canMsg[6] * 256 + canMsg[7]; // volt 2
      break;

Two of the modules have only 4 cells each and the corresponding messages contain 00 or FF.  See the screenshot below for messages 0x6C3 and 0x6C4.

A photo of a CMU sitting on top of a 4 cell module:

To be continued...

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