Guidance needed on laptop battery problem

Discussion in 'General Electronics Chat' started by systemloc, Aug 4, 2005.

  1. systemloc

    Thread Starter New Member

    Aug 4, 2005
    2
    0
    Hi,

    I know something of electronic theory. I've built simple things like PWMs and such from scratch. I'm not sure if this is the best place to ask, and I'm very open minded, so any pointers to other resources are greatly appreciated!

    I have an old Pentium 100 Gateway laptop. It functions fine off of its AC->DC power converter. When I first recieved it (used), it ran for about 5 minutes off of its battery after being charged. Now, however, it will shutdown immediately after emiting a low battery warning. This is not in any way software related, as the warning and shutdown are all controlled by the laptop's own firmware. I have checked out the battery with a professional, and the NiCd cells themselves are in fine condition. They hold a charge and sustain reasonable opperating loads for extended periods. It's my conclusion that the laptop cannot read the battery level correctly and believes the battery is dead in error. The battery unit contains an IC that connects to the laptop via a lead along with the VDC and ground. I believe it's some sort of serial comm chip. I tried preventing the chip from making the connection with the laptop with no apparent change in behavior. I'm at a loss how to proceed. I would be happy if I could simply disable the laptop's ability to sense battery level at all and fool it into thinking it was at 100%.

    I'm hoping someone could shed light on how the system might be designed to monitor power level, and/or what to look for inside the battery or laptop to gather more information.

    Thanks!
     
  2. systemloc

    Thread Starter New Member

    Aug 4, 2005
    2
    0
    I went ahead and pulled the machine and battery apart and began identifying what I could. I'm posting it here in case someone can better enlighten me.

    There are two different ports to contain a battery on this laptop. Certain ICs are located around both ports. Since they are duplicated for each port, I surmise that they must serve some function that relates to the battery. There are two ICs labeled "712 NDS9430" which I believe are P-Channel MOSFETs. There is one IC labled "BA7786FP 718 151 Y" near one port. I have identified it as an audio chip that creates the system beep. Near the other port is an IC "BA9700AF" which is a switching Dc/Dc regulator.

    Inside the battery assembly, there is a chip labeled "KLIXON® 7-s 4MM75X 09 07 J" wired to the batteries and nothing else that I cannot identify. There is also a large (1/2" x 3/16") metal cylinder with alphanumerics that I can't easily read wired to the batteries alone that has one pointed end. Reminds me of a diode, but why? There is a PCB which the VDC and GND are connected to with 5 leads that hook up to the laptop. On the board are some diodes, a chunky resistor and two ICs. One is "68AB LM35D" which I have identified as a temperature sensor. The other is a "bq2010 9636D107" which is a battery power monitor.
     
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