Dell Power Adapter - hardware or firmware (BIOS) control?

Discussion in 'BIOS Mods' started by swmspam, Jan 11, 2012.

  1. swmspam

    swmspam MDL Novice

    Jan 11, 2012
    The Dell power adapters have a Dallas DS 2501 1-wire memory chip that transmits a binary code through the center pin of the power supply cable. Since these pins break very easily, or the wire inside of the shielded cable fails often, I have a pile of Dell power adapters that still deliver power but do not transmit the code. A few google searches show this is a common problem, but not many solutions other than purchasing new power adapters. It seems wasteful to dispose of perfectly functioning power adapters because of the flimsy dictatorial obsessive-controlling circuits are the first parts to break.

    The laptop will enable/disable battery charging depending on the receipt of the adapter code. If no code is received, no battery charging, regardless if the power adapter is otherwise healthy.

    Is this decision made in hardware (in the power circuitry) or in firmware (in BIOS)?

    There is a great reference for this, but the forum denies me of posting links. Find detailed hardware analysis of the Dell power adapters at (remove spaces):
    www . laptopbattery4 . co . uk / blog / dell-ac-power-adapter-type-cannot-be-determined-solution
  2. tqhoang

    tqhoang MDL BIOS Modder

    Apr 29, 2008
    This is likely in the Embedded Controller (EC) firmware.
    Stop hovering to collapse... Click to collapse... Hover to expand... Click to expand...
  3. swmspam

    swmspam MDL Novice

    Jan 11, 2012
    I originally thought the adapter control was done by a separate microcontroller (since my first d600), but recently have been rethinking my conclusion. The newer Latitudes (such as my e6220) prerelease BIOS had a "AC Battery Charging Behavior" setting that could disable the power adapter from charging the battery from BIOS. This opens the possibility that the charging control may be done by BIOS, although the actual decryption of the adapter code may be done elsewhere.
  4. gabiz_ro

    gabiz_ro MDL Member

    Feb 2, 2010
    That's 100% correct.
    Most if not all of charger controller are managed through SMBUS. EC detect type of charger and let charger IC to communicate with battery controller.

    For more info read some datasheets like MAX8731 (smart charger with SMBUS) and some BQ2085 series (battery fuel gauge with SMBUS)
    Since charger cannot comunicate with battery will not pass any current to battery,same thing with battery,since cannot comunicate with smart charger will not let any voltage to go to battery.

    As I see only way to bypass this is a EC firmware mod.
    Many are based on 8051 CPU but withouth any datasheet is a very hard work, and any mistake could brick your laptop forever (unless EC is reflashed or replaced)