Can't find bq20z955 datasheet (battery management chip?)

[nuno]

Anyone has this chip's datasheet? Is on a Packard Bell (Acer) notebook battery, cells seem good but Windows reports "not charging".

[amyk]

According to https://e2e.ti.com/support/power_management/battery_management/f/180/p/61751/379023 and https://e2e.ti.com/support/power_management/battery_management/f/180/t/62507 it's a custom chip for some manufacturer so you're going to have to find some "insider" chummy enough to give you the details... good luck.

[nuno]

Just perfect... has locking keys and all...
Thanks for the links.
Need to think what am I going to do with this.

[nuno]

Well, there's some information:
http://www.ti.com/product/BQ20Z95
Original name: bq20z95

[nuno]

Ok, I get it... The battery cells are ok, but for some reason some event led the chip to enter a "permanent failure" mode, where the battery is basically dead and it will not let it be charged. It is possible to clear the failure from the chip, but you need the "battery manufacturer's password"  ...

[Jwillis]

Are you sure the cells are functioning properly? Did you test each individual cell or the whole pack.Even with one faulty cell inside the pack will put the charging in safe mode and will  not charge .
Same thing happened to me with and HP Envy Ultrabook 6.Replaced the pack and everything was fine.Opened up the old pack and found one cell was dead and it would not take charge and the rest were all good .Only takes one cell to put those packs in the trash heap.Such a waste.

edited for better explanation.

Battery packs ,specifically Lithium, are designed in a series parallel configuration. Lithium batteries charge fine in  parallel but not well in series.So the pack is charged by splitting the parallel cells from the series cells .This is called balancing.Theirs a PCB inside the pack that does this.The charge controller detects how those individual parallel batteries are charging and switches them accordingly.If it detects that one parallel set isn't charging correctly it goes into safe mode.This is a safety feature built in to prevent fire by charging bad batteries.     

[nuno]

There are 4 prismatic cells in series in this pack. Unfortunately I didn't realize the problem on time (that it was not charging; I have it connected to mains most of the time) and when I put my hands on it, the cells were already drained to near 0V. I removed them from the pack and slowly brought them back to a normal voltage then charged them normally to some 20% of full. They all charged normally and held the charge, and all have roughly the same internal resistance.

[Rasz]

liion that went near 0v is garbage

[Jwillis]

I agree with Rasz . The batteries are garbage replace the pack.