Cannot identify balancing wire of laptop battery - tension between the different wires does not make

I need help identifying the balancing wires of a laptop 3 cells battery - the tension I measure between the different wires does not make sense.

I have a laptop (Toshiba Chromebook 2) with a 10.8V li-ion battery (3 cells).
I am trying connect an external powerpack made of 3 18650 cells, in parallel with the laptop's battery.
Like this:
- https://sites.google.com/site/keyboarddriver/laptop-battery-mod---adding-more-batteries

- https://sites.google.com/site/keybo...g-more-batteries/step-4-soldering-and-testing

The idea would then be that I can either charge this external powerpack with an RC lipo/li-ion charger, OR if connect to the laptop, then the laptop power supply would charge both the internal battery, AND the external powerpack.

However, I am having trouble finding the balancing wires of the internal battery.
If I measure the tension between the +ve and -ve, I get 12.5V when fully charged, but for the balancing cables, I don't get plausible values (either it's too heigh (9.15), or too low 3.16 / 3.27).

The laptop's battery is:
http://www.laptop-battery-shop.com/toshiba-pa5208u1brs-108v-3860mah-original-batteries-p-5298.html

The internal battery has 9 wires:
1-2 : RED
3 : Yellow
4 : Blue
5 : White
6 : Green
7 : Orange
8-9: RED

Here are the tensions between the different wires:

FULL BATTERY (37Wh):

2-3: 0.13V
2-4: 12.48V
2-5: 12.07V
2-6: 9.15V
2-7: 9.15V
2-8: 12.48V

3-4: 3.16
3-5: 2.83
3-6: 0
3-7: 0
3-8: 3.16

4-5: 0.30
4-6: 3.28
4-7: 3.28
4-8: 0

5-6: 2.95
5-7: 2.95
5-8: 0.30

6-7: 0
6-8: 3.28

7-8: 3.28


EMPTY BATTERY (1.5Wh):

2-3: 0.13
2-4: 10.08
2-5: 9.72
2-6: 6.77
2-7: 6.77
2-8: 10.08

3-4: 3.16
3-5: 2.84
3-6: 0
3-7: 0
3-8: 3.16

4-5: 0.30
4-6: 3.28
4-7: 3.28
4-8: 0

5-6: 2.95
5-7: 2.95
5-8: 0.30

6-7: 0
6-8: 3.28

7-8: 3.28

Thanks a lot in advance for any feedback!