Thinkpad R61 cannot boot twice

[gdro]

I have power problems with a 2006 Lenovo Thinkpad R61 (8918). I can't boot it twice without having to wait a few hours in between. After say 6 hours of charging, I can boot it and work for hours but the minute I shut it off, if I restart it it won't go past the bios. I can, for example, press F1 to enter bios but it will or will or not have time to enter the bios settings menu before power cuts 1-2. Then I need to disconnect the battery and AC adapter to restore power. And now I'm good for some more 6-8 hours of charging beore I can complete a boot up again.

The laptop battery had been dead for a few years before I recently bought a new one, thinking that it would solve the power problem, which started to occur after a few years of using it with the dead battery in and always connected to the charger. I had also replaced the fan back then at some point, to fix fan errors that would prevent it from booting.

New battery keeps its charge and fan works good. CPU temp stays around 55-65°C when I'm using the laptop.

My problem has similar characteristics to the ones in this thread:
http://www.tomsguide.com/forum/64361-35-laptop-turns-shuts-seconds-later-laptop

I suspect the CMOS battery is involved but I'm not sure since bios settings are not lost between each power cut. Does the CMOS battery need to have enough power to support booting or if its power is only used for keeping bios settings and time?

Any suggestions will be much appreciated. It's an old laptop but it's perfect for my needs so don't want to buy an other one if possible. Thanks.

 

[hang-the-9]

Does the system work fine without the battery?

 

[gdro]

no, it's same with or without the battery. I was thinking about updating the bios in the hope it would fix my problem but I fear that a potential power cut during the process would make things worse.

 

[ffg7]

cmos battery not needed for booting as it sounds like a motherboard issue. try this, remove main battery from laptop, disconnect power adapter from laptop, hold the power button down for a 20 count, reconnect power adapter & turn on laptop. after getting into windows, do the proper windows shutdown then try to power up again. if works then try 3 more times & if still works then install main battery & see if still works.

 

[gdro]

just tried what you suggested: almost completed 1 boot and then power has cut (no led on, nothing). it may be because I spent some time in boot order menu, to keep the laptop from trying the cd drive. Second time, I did the 20 seconds thing with battery and adapter out. Plugged the adapter back in and booted successfully. I shut it down and tried another time to boot it: couldn't get to the GRUB menu. Tried the 20 second thing again, then couldn't get passed bios.

 

[gdro]

thanks for your help. how would I find if the mobo's a problem? do I need to remove one component at a time (ram, hdd) and see what it does, as described in the thread I referenced in my first post?