HP Envy 17tbw000 not detecting battery.

[redbaron1007]

Hi all, I've got an HP Envy 17tbw000 with a haymitch 2g mb 17888-1 motherboard that isn't detecting batteries. I've tried two different batteries and it doesn't detect either of them. I have a donor board with a dead CPU I've been pulling parts off of. I replaced the BQ25708 IC as well as two 10.5 ohm connected to pins 19 and 20 that were reading ~100-200 ohms and had physical damage on the top of the package. I also tried replacing the fets on the battery charge circuit because I had spares and all of this hasn't changed anything. I don't have a schematic so I can't find the 10kohm resistors that the datasheet for the BQ IC says should be present on the smbus pins 12 and 13. I have already read through https://www.badcaps.net/forum/showthread.php?t=90356 and is how I got into looking at the smbus and trying to find those resistors.

I have also tried reflashing the bios and have had no success with that either. The laptop will turn on when the charger is plugged in, but shows the battery as unidentified. With the new battery it will stay on for a few minutes when the charger is unplugged. When I check the battery voltage when the laptop is not plugged in I get 0V across all pins, but when the charger is plugged in I get 9.04V on + and 3.05V-3.07V on /,D,and C pins and 0V on gnd.

I have had no luck finding any schematics or any other information about this fault other than others asking for the schematic.

I forgot to bring the pictures of the board I took with markups on them home with me when I left work today, but I can upload those tomorrow if it would help anyone.

[mon2]

Re: HP Envy 17tbw000 not detecting battery.

Locate the vcc power pin for the bq charger ic. There should be a 3 pin dual diode nearby. This diode powers the charger ic. Check that there is power for all cases.

Adapter only.
Battery only.
Adapter and battery together.

The higher of the 2 power sources will power the charger ic.

Confirm the above.

[redbaron1007]

Re: HP Envy 17tbw000 not detecting battery.

I checked the voltages and get following on pin 1 VBUS

Adapter only 19v
battery only 0v
Adapter and battery 19v

I don't get any voltage coming from the battery when the adapter isn't plugged in. When I disconnect the charger The voltage on the battery goes from 10v down to about 2v and then back to 0v. I have access to the tabs coming off the battery to the control board and I do have ~2.9v-3v on each of the three cells in the battery. All three cells are within .005v of one another. The cells were reading higher yesterday when I was working on the laptop ~3.5v. If I leave it on the charger for a few hours the voltage goes back up and the laptop does seem to be charging the battery.

[mon2]

Re: HP Envy 17tbw000 not detecting battery.

Are the batteries you have tested known good ones and compatible with the motherboard? It is possible that the bms is locked out.

Suggest for you to source another battery pack from Amazon which is risk free and test again. You can keep or return the battery pack if it is not required.

Be sure the battery pack smbus lines are reaching the charger ic. Confirm it with a meter in resistance mode with no power to the board. Remove the battery and check the resistance from the battery connector contacts to the charger ic.

[redbaron1007]

Re: HP Envy 17tbw000 not detecting battery.

Are the batteries you have tested known good ones and compatible with the motherboard? It is possible that the bms is locked out.

Suggest for you to source another battery pack from Amazon which is risk free and test again. You can keep or return the battery pack if it is not required.

Be sure the battery pack smbus lines are reaching the charger ic. Confirm it with a meter in resistance mode with no power to the board. Remove the battery and check the resistance from the battery connector contacts to the charger ic.

One of the batteries is the one that was the original one from the laptop that the owner replaced with one they bought from HP. The other one is the one they bought from HP directly that was also having the same problem.

I ended up buying a replacement battery for cheap off amazon to test with and rule out the batteries, but it's still got the no battery detected issue.

I checked the smbus lines and was getting ~2 kohm on one of the lines and ~4 kohm on the other. I don't remember which one was which.I wrote it down, but left my notes at work. From reading the datasheet for the bq chip there's supposed to be a 10 kohm resistor somewhere between the IC and the smbus pins on the battery connector so I was expecting higher resistance values. I couldn't tell from the datasheet if the 10 kohm was a requirement or a suggestion.