Orbea range extender modification

[Wgm20]

Hi- first time poster, apologies if this isn’t the right forum.

I have a 2017 focus jam2. The battery is small. I read this, which suggests you can use a 36v battery as a simple range extender
provided its live: Making your own tec pack? - EMTB Forums

I liked the packaging of the orbea range extender and thought I’d try to make this work (for fun too).

On the orbea battery, I measured all the output terminals and none were 37.5v. When I open it up, I see the following:

 

[Wgm20]

So C is a bit of a mystery. As all lines bar C are 0v, my initial guess was that, if it has a switch, one of T1, T4, B4 probably gets connected to that, and it may turn on A to +37.5. Does this seem like a reasonable guess?

 

[Wgm20]

I’m also a bit surprised to see C+ and P+ on the board- the only wiring diagrams I’ve seen for any BMS on the web have had C- rather than C+ (I’m assuming C means charge). And they’ve shared P+ rather than P-.

 

[Wgm20]

All advice appreciated- I am a complete newby to electronics!