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I buy an used notebook (Sony Vaio SVF152C29X), its only defect is that it doesn't charge the battery, it only works plugged in the power supply (19.5V and 6.2A output).

I don't know if the battery doesn't charge because it's dead or if it is a notebook defect.

I used a multimeter (in DCV position) to measure the output in the notebook terminal (where I plug the battery) and it shows 19V. But the battery specification is 14.8V/2670mAh/40W (it is a Sony VGP-BPS35A).

Is there something wrong with the notebook or it do exists batteries 14.8V that charges with 19V voltage? Or the battery can have a smaller transformer inside it?

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There must be 1 step down converter with current and voltage control for the battery pack ( which is most likely dead or very weak) and then many step down regulators for the motherboard for CPU, GPU, RAM, I/O. So the 19V is just a universal charger + mobo driver voltage and you're just reading the voltage just stored by the charger there recently, which you ought to be able to pull down with xx K resistor as it ought to be reverse current diode protected.

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  • \$\begingroup\$ Its battery is a 4-cell in series. It came with two batteries, an old one (that I open and get 9V), as I can read the voltage in the entire serial pack os cells, there is no dead cells in it, am I right? The other battery is newer, the voltage in the entire pack is 15V, the notebook should be able to turn on using this battery, shouldn't? I think that the owner try to buy a new battery and it didn't resolve, so, he sell the notebook. \$\endgroup\$
    – lmcarreiro
    Commented Nov 18, 2017 at 9:43
  • \$\begingroup\$ My multimeter has only one DCV position, that is a 1000 DCV, so, the 15V may be a 14.8V (same as the battery specification) \$\endgroup\$
    – lmcarreiro
    Commented Nov 18, 2017 at 9:44
  • \$\begingroup\$ I just saw some videos of li-ion batteries in fire, I won't try to fix these batteries. \$\endgroup\$
    – lmcarreiro
    Commented Nov 18, 2017 at 10:04

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