X380 Yoga battery how to jumpstart BMS?

[likengmx]

Hi. Trying to recover a battery for X380 Yoga.
Nominal Voltage is 15V but it had only 7V and doesn't charge.
My idea is that probably this battery was without use long time and it has auto discharged. So I disassembled it, it has 4 cells li-poly 3.82V. I charged them individually and now battery has 15V, but bms board, battery controller, doesn't output power.
With old thinkpad batteries you can restart, jumpstar the bms, joining its positive output with positive from cells. But it doesn't seem to work with thinkpad yoga batteries.

Does anybody know how to jumpstart the BMS of new thinkpad batteries?

This is the board and its pins:

Output connector to laptop, 9 pins:

+ + + C D T - - -

where C D T are comms.

BMS connection to cells in order left to right, with names in board:

VL First cell positive
VG Ground, negative
VM2 Second cell positive
VH Third cell positive
VM1 apparently same voltage than VM2
VP Positive 15V

Other contacts in board, I don't know function

VH JP same voltage as VH
VP JP same voltage as VP
2nd JP same voltage as VP

[likengmx]

OK. I have been informed in badcaps.net forum that modern batteries BMS cannot be jumpstarted.
Once the controller locks the battery, the controller has passwords and also you need to reprogram the controller with special tools.

[kfzhu1229]

OK. I have been informed in badcaps.net forum that modern batteries BMS cannot be jumpstarted.
Once the controller locks the battery, the controller has passwords and also you need to reprogram the controller with special tools.

yes indeed that is true. That is true for practically all laptop batteries from the 2010s and later, after the whole saga of exploding Dell and HP batteries with sony cells, manufacturers had "one more reason" for more evil BMS' that will erase its own existence after the slightest overdischarge. Not helping many laptop battery packs nowadays use custom ordered BMS chips without even a pinout chart officially released to the public.
My only luck with "rebuilding" a "modern" battery pack outside of using aftermarket BMS is on on an internal 6 cell (still 18650) Acer battery from 2011 where I swapped 3 of the 6 cells without ever disconnecting the other 3 cells (and with all of them discharged to the around same 3.6V). this way no programming is required. The wear count just went down over time with use to the right level.