Lenovo N500 won't boot, no fans, only blue LED light

[MrOtto123]

My Lenovo N500 laptop has been sitting without a battery for a few years.

I tried it now, charged the battery, but there is no post, no boot, no fans, only blue led light on for a few seconds. I have disconnected all devices, and tried another cpu and ram, but no luck, same blue led light for a few seconds. I have tried to remove power and battery and holding the power on for a minute, but doesn't work.

I remember I had the same problem the last years I used it, and unplugging battery and power and holding power button fixed this.

Could a dead CMOS battery be a problem? Should I desolder it and replace it? This is the only way to reset BIOS if the battery is not dead?

[RealBlackStuff]

Try booting without main battery, only charger attached.
Press Esc if/when date/time is asked for.
If that doesn't work and CMOS is dead, you cannot set date/time and without that, the laptop cannot start up.
So yes, replace the CMOS.

[MrOtto123]

Thanks. I have tried without the battery and only the charger. Same symptoms, no fans and only blue LED light for 5 seconds.

I will replace CMOS battery. I am almost certain it is discharged completely.

[MrOtto123]

I measured the CMOS battery. It read 2.48v when not battery or charger was connected. So it seems to be in order. Should I desolder it to reset the CMOS, or do I have to replace the CMOS chip?

[MrOtto123]

Desoldered the battery, it says 3v spec. Sanyo ML12-something (ML1220?), can't make it out. 2.48v, possibly to low voltage to maintain CMOS?

https://i.imgur.com/Op74osi.jpg
https://i.imgur.com/g3LQ5n1.jpg

[RealBlackStuff]

You need ~3V or better.

[MrOtto123]

Thanks. I have ordered a new solder in battery.