X380 Yoga battery how to jumpstart BMS?

[Liken]

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

[Vesko356]

Re: X380 Yoga battery how to jumpstart BMS?

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?

Yes I know - you can't "jumpstart the BMS" on a modern laptop battery like it was done years ago with "old thinkpad batteries" on YouTube.

https://www.badcaps.net/forum/showth...81#post1241581

.

[Liken]

Re: X380 Yoga battery how to jumpstart BMS?

OK. I didn't know that modern batteries were so protected, even with passwords. Thank you.

However, I have not done any cell replacement, and the bms has not lost voltage at any time while charging the cells individually. I understand that it doesn't matter, once it locks for whatever, goodbye.

[sam_sam_sam]

Re: X380 Yoga battery how to jumpstart BMS?

This does not matter because once you have passed a certain amount of watt hours then on some BMS protection boards it locks the system out and in some cases it can not be unlocked from what I have read

I have one question what is the voltage on each group of battery cells because if they are more than 0.050 volts from each other some BMS boards lock out because of this if this is the case you can try rebalancing the battery cells but I caution you that you need to be extremely careful about not letting the voltage to go below 2.8 volts pre battery cells because some BMS boards lock out the output voltage and will not allow it to be reset unless you remove all power from the circuit board but some of them if it has a micro controller it locks it permanently and it will useless

One thing you can try is to bring down the voltage to about 9.0 to 9.5 and see if it will charge or not but make very sure that your battery voltage are exactly the same on each battery cell grouping if this does not work I no other suggestions for on this because I do not play with laptop battery packs because they are a pain in the a** to deal with

The easiest way to do this is to use an automotive light bulb like a 1157 or a M16 20 or 50 watt do each group of battery cells individually and stop the discharging cycle when they reach 9.5 volts

When you reconnect the battery pack to the laptop do not have the power supply turned on until you have the battery pack installed then hook up the power supply to the computer and see if this will reset the BMS board

[Liken]

Re: X380 Yoga battery how to jumpstart BMS?

I have one question what is the voltage on each group of battery

When I disassembled it the cell voltages were:

c1: 0.41V
c2: 1.82V
c3: 2.47V
c4: 1.91V

The first one was very very low. However it was charging fine for hours with 0.5A. Then I charged the rest of them and they are balanced at 3.8V +- 0.04V tolerance.

It seems clear that there were reasons for a BMS lock.

Why are you talking about 9V, Is it some special voltage range? The nominal voltage of the battery is 4 x 3.8 = 15.2V

[Liken]

Re: X380 Yoga battery how to jumpstart BMS?

Do you think it would be a viable idea to buy a cheap 4S BMS 20A board, 2$ in Aliexpress, and solder its connections to the existing BMS?

It would be like a bridge VP to Out + but keeping safety. And the original BMS establishs the required comms. The question is, can the original BMS, through comms with the computer, inhibit the charge and discharge from the mainboard side?



I use Linux and, although battery is dead for charge and discharge, I can see its voltage. And BIOS needs to acknowledge the battery to boot.

(By the way, I have seen that the fuse of this BMS is DS5A4, I have not checked whether it is blown or not)