Hacking the i3 battery modules connector – part 2

Wiring the connectors

Now that I have the connector male that fits the i3 female connector, here are my next steps for the battery to BMS cabling:

• Get 1mm electric pins 
• Get some 20 AWG wire 
• Solder the pins to the wires 
• Solder the wire to the pin, then add some markers  to track where the wire leads to the battery (see below more about the mapping of wires in the module)
• I have used masking tape to make a tab where I could write on the code for the wire terminal
• Isolate wires with shrink tubes
• Glue and isolate the wires and connector lid.

Mapping the modules wiring

Looking at the connector as a grid 13x2 (cols x rows) this is my mapping.

for row 1 we have

Pos 1 - empty

Pos 2 - White & red wire - cell 12+

Pos 3 - White - cell 9+

Pos 4 - White & red - cell 8-

Pos 5 - Black & green - cell 6-

Pos 6 - Black - cell 3+

Pos 7 - Black & green - cell 2-

Pos 8 - Brown - cell 1- (there are 2 wires going to the same spot)

Pos 9 - empty

Pos 10 - Yellow - Thermistor in cell 7+

Pos 11 - Yellow - Thermistor in cell 7+

Pos 12 - Yellow - Thermistor in cell 2+

Pos 13 - Yellow - Thermistor in cell 2+

For row 2 we have

Pos 1 - White wire - cell 12+

Pos 2 - White - cell 12+ (there are 2 on the same cell)

Pos 3 - Red - cell 10+

Pos 4 - White - cell 9-

Pos 5 - Red & black - cell 6+

Pos 6 - Brown - cell 5-

Pos 7 - Back - cell 2+

Pos 8 - Brown - cell 1-

Pos 9 - empty

Pos 10 - Yellow - Thermistor in cell 4-

Pos 11 - Yellow - Thermistor in cell 4-

Pos 12 - Yellow - Thermistor in cell 9-

Pos 13 - Yellow - Thermistor in cell 9-

About the temperature sensors

The thermistors to check the temperature fitted on the i3 BMW modules have a different resistance compared to the 4 thermistors that came with my ANT BMS.

BMW are rated 125 kohm

ANT in my box are 13.2 Kohm (if I'm correct)

The difference of 110 Kohm ~

 
I hope that I can configure some parameters in the BMS to keep using the original BMW sensors. If the configuration is not available in the BMS I wonder if it would be possible to use a resistor to change the resistance value and take it to a range that the BMS can work with?

Ref found: 

https://www.sensortips.com/temperature/designing-with-thermistors/

https://www.embeddedrelated.com/showarticle/91.php

Please let me know if anyone has any experience of similar hacks and what other approaches would you take.