Thinkpads Forum

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?

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.

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.

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?

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

You need ~3V or better.

Thanks. I have ordered a new solder in battery.

I soldered in a new battery and installed my upgrade CPU and 2x2gb ram, and it booted, fan and Bios started. I also managed to start my 10 year old Windows 7 pro.I also managed several restarts no problem.

Then I attached the wifi cables and installed some chassis screws, and now I have the same problem, just blue power light for 5 seconds, then off no sceen, no fan.

I tried to solder and resolder the CMOS battery, no luck.

What do I do? What is the problem?

I read 2.69v when battery is attached.

Looks like a bad/dying CMOS again, but also a bad/dead wifi card (Intel 5100?)
Look for an Intel 6200 or 6300, hoping there is no wifi-whitelist.

I bought two new batteries, both are 2.7v

The wifi card was connected when computer worked, just not the antenna cables. I tried to remove the card, but it wouldnt boot.

The CMOS battery shows just 0.05v when power is connected, no main battery inserted

How do I get it to boot?

If the new CMOS is also a rechargeable one, such as Maxel/Sanyo ML1220, when charged it should have 3V (or more).
If so, let it sit overnight (or a bit longer) with charger plugged-in to charge that CMOS first.
But if you bought ordinary (non-rechargeable) CR1220 batteries, you probably got NOS (New Old Stock) depleted batteries, that have been lying around for a few years...

It's a ML1220 rechargeable battery.

Desoldering negative on battery on board and leaving it overnight and resolder and try to start up with power connected and no battery connected did not work. Just blue light, no fan or boot.

How do I reset bios?

Why do I only read 0,05v higher on the battery when both battery and power is connected?

How do I get it to boot? Do I need to disconnect all components and desolder battery again?

To charge that CMOS, both connectors need to be soldered to the motherboard, then plug it in and charge overnight.
If no luck, the charging circuit on the mobo may be faulty.
Don't forget that laptop is about 15 years old!

I will try and connect a C2032 battery with taped wires on battery, and solder on the wires to the board.

How do I reset the bios?

If you can get into BIOS, usually you press F9 to set it to default, then press F10 to save and exit.

No fan, no post, no LCD, no bios, no beeps, no error messages. Just blue light on for five seconds.

Thinking of buying a replacement mainboard from aliexpress, these are tested before sale, for a non-nvidia gpu mainboard, with GM45 chipset, not PM45, probably less heat without the nvivdia gpu, I don't need any 3D-capabilities, so the GM45 chipset with the integrated graphics and the HDMI port would be sufficient. Maybe also a more durable design of the mainboard without the nvidia chip on it.