Sony Vaio vgm fw21m Battery not detected

[anotherdude]

Picked this laptop up for £20 a few weeks ago supposed "motherboard fault" anyway reinstalled windows 7 all is fine apart from the battery, windows says "battery not detected"

Multimeter reports back that 0.00 is output from the battery, so I opened the battery up to check the cells,measuring the plus and minus of the battery circuit I see a few volts, not sure what the exact number was.

So I hooked up a 10v output to the + and - and gave it five minutes, came back and removed the output and measured the batteries again, this time the voltage is sitting at about 5-6v and slowly dropping.

So i'm assuming that the pcb the batteries are attatched to is defective, anyone any info on this or have done similar.

Have read about thermal fuses in these and that the pcb's can sometimes fail but can't find any information directly related.

Battery is vgp-bps13a

[kc8adu]

Re: Sony Vaio vgm fw21m Battery not detected

measure each group of cells.
any below 3v may have locked out the management chip.
sounds like its just a bad pack.
if voltages go out of bounds it shuts off the switch mosfets to the output.
you might try to charge the cells till over 3v/group but if they were way low they are not going to be much use.can also be dangerous to recharge dead cells.

[Th3_uN1Qu3]

Re: Sony Vaio vgm fw21m Battery not detected

measure each group of cells.
any below 3v may have locked out the management chip.
sounds like its just a bad pack.

Yes. There is also an EEPROM inside which stores that info, so you can say goodbye to the battery pack.

[anotherdude]

Re: Sony Vaio vgm fw21m Battery not detected

thnks guys, will just order a new battery then, at least I know the laptop is not at fault

[dj_ricoh]

Re: Sony Vaio vgm fw21m Battery not detected

The BMS system can lock its self when you desolder the cells.
Does making the battery dead.
In order to cheat it you need your new cells to be at the same value(voltage).
Then solder them in parallel so the bms system wont fell that there are no cells.
After that you take the old cells out.

You need to do discharge and charge a few time untill you manage to see every thing ok.

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