HP 350 G1 with charging related issues, need help!!!

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  • classicandy
    Badcaps Veteran
    • Apr 2018
    • 308
    • Nigeria
    #1

    HP 350 G1 with charging related issues, need help!!!

    Hi, I have this HP 350 G1 that gives out about 16.8v on the battery (+) terminal in the battery connector on the motherboard WITHOUT a battery inserted. It should be around 2.8v without battery inserted. The battery charger IC is BQ728.

    I have searched online but haven't found the schematic diagram yet. HP 2000 uses same battery charger IC, so its schematic diagram can work for it in terms of its charging circuitry.

    I have attached the schematic diagram for HP 2000 as well as images of the charging section of the HP 350 g1.

    I would be very grateful for your help.
    Attached Files
    Tags: None
    • classicandy
      Badcaps Veteran
      • Apr 2018
      • 308
      • Nigeria
      #2
      Re: HP 350 G1 with charging related issues, need help!!!

      I have tried replacing the battery charger IC (BQ728) but no luck

        Comment

        • mon2
          Badcaps Legend
          • Dec 2019
          • 14023
          • Canada
          #3
          Re: HP 350 G1 with charging related issues, need help!!!

          Remove all power.

          Meter in resistance mode.

          Check the resistance of the mosfets linked to the battery.

          Source (1-2-3) & drain (5-6-7-8)
          Source & gate (4)
          Drain & gate

          Start with Q6012 which is the battery mosfet. Post the measurements.

            Comment

            • classicandy
              Badcaps Veteran
              • Apr 2018
              • 308
              • Nigeria
              #4
              Re: HP 350 G1 with charging related issues, need help!!!

              Originally posted by mon2
              Remove all power.

              Meter in resistance mode.

              Check the resistance of the mosfets linked to the battery.

              Source (1-2-3) & drain (5-6-7-8)
              Source & gate (4)
              Drain & gate

              Start with Q6012 which is the battery mosfet. Post the measurements.
              Ok, thanks for the fast response. I'm taking readings now

                Comment

                • classicandy
                  Badcaps Veteran
                  • Apr 2018
                  • 308
                  • Nigeria
                  #5
                  Re: HP 350 G1 with charging related issues, need help!!!

                  Originally posted by mon2
                  Remove all power.

                  Meter in resistance mode.

                  Check the resistance of the mosfets linked to the battery.

                  Source (1-2-3) & drain (5-6-7-8)
                  Source & gate (4)
                  Drain & gate

                  Start with Q6012 which is the battery mosfet. Post the measurements.

                  Q6012

                  Resistance Mode (200M ohms)

                  Drain & Gate
                  Black Probe on Gate/Red on Drain = 3 ohms
                  Red Probe on Gate/Black on Drain = No readings, probably above 200M ohms

                  Gate & Source
                  Black Probe on Gate/Red on Source = No readings, probably above 200M ohms
                  Red Probe on Gate/Black on Source = 2.8 ohms & dropping, (slows down around 2.5 ohms)

                  Source & Drain
                  Black Probe on Source/Red on Drain = 2.71 ohms (dropped from 3.01)
                  Red Probe on Source/Black on Drain = 2.05 ohms

                    Comment

                    • mon2
                      Badcaps Legend
                      • Dec 2019
                      • 14023
                      • Canada
                      #6
                      Re: HP 350 G1 with charging related issues, need help!!!

                      Can you share or confirm the readings ? Post the pic of your meter to verify.

                      200M = 200 Mega ohms is the max.

                      If '3' reading, then it is 3 Mega ohms ? That is ok if understanding is correct.

                      Check the next mosfet in the same way for the high side charging leg for the battery.

                        Comment

                        • classicandy
                          Badcaps Veteran
                          • Apr 2018
                          • 308
                          • Nigeria
                          #7
                          Re: HP 350 G1 with charging related issues, need help!!!

                          Originally posted by mon2
                          Can you share or confirm the readings ? Post the pic of your meter to verify.

                          200M = 200 Mega ohms is the max.

                          If '3' reading, then it is 3 Mega ohms ? That is ok if understanding is correct.

                          Check the next mosfet in the same way for the high side charging leg for the battery.
                          I think it is 3 Mega ohms

                          Also, I just noticed, It goes to 16.9v (from 2.3v) when powered on without battery inserted and goes back to 2.3v after some seconds when powered off.

                            Comment

                            • classicandy
                              Badcaps Veteran
                              • Apr 2018
                              • 308
                              • Nigeria
                              #8
                              Re: HP 350 G1 with charging related issues, need help!!!

                              Originally posted by classicandy
                              I think it is 3 Mega ohms

                              Also, I just noticed, It goes to 16.9v (from 2.3v) when powered on without battery inserted and goes back to 2.3v after some seconds when powered off.
                              I have checked another motherboard using same battery charger IC (BQ728) and it doesn't behave like this.

                              Is it normal for this HP 350 g1 to behave differently despite using same battery charger IC with other motherboard ?

                                Comment

                                • classicandy
                                  Badcaps Veteran
                                  • Apr 2018
                                  • 308
                                  • Nigeria
                                  #9
                                  Re: HP 350 G1 with charging related issues, need help!!!

                                  The laptop behaves in a weird way such that if i power it on, it will work well for some time like few minutes and might trip off, and if i try to power it back on, it might turn on and turn back off almost immediately and the white light would go off as well, until i unplug the charger and leave the motherboard for a while (probably to cool down) and try to power it on again before it comes on for some time.

                                  It doesn't get too hot when on. Its just normal operating temperature, so i can't suspect its due to overheating

                                    Comment

                                    • mon2
                                      Badcaps Legend
                                      • Dec 2019
                                      • 14023
                                      • Canada
                                      #10
                                      Re: HP 350 G1 with charging related issues, need help!!!

                                      Carefully measure the voltages on each pin of the charger IC.

                                      It is possible that the charger IC believes there is a battery connected so it is enabling the charging mosfets.

                                        Comment

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