CMOS Batteries

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hjanzen · #1 Post by **hjanzen** » Wed Feb 09, 2011 8:51 am

CMOS batteries in Thinkpads like f.i. the 600 series use simple and cheap type CR2025 or 2032 batteries connected by 2 wires and a plug to the mainboard.
These batteries are not rechargeable, but last quite a number of years before they die.
Other laptops, like the 701c and the 240 series use rechargeable batteries.

Some months ago the battery of my 701C died and I got the 161-163 warning.
I removed the battery and soldered a similar 3V rechargeable substitute.
After that no warning any more and the laptop started normally.
Since than the laptop has been sitting idle on the shelve.

Recently I tried to start it and to my surprise the annoying 161-163 warning appeared again.

Does that mean that one should regularly use the laptop, just to make sure that this type of CMOS battery is permanently charged and keeps its load? Or could there be another reason, laekage (?) somewhere at the main board , causing the battery to die that soon.

I do hope to get an expert's view on this matter.

Hans

#2 Post by **RealBlackStuff** » Wed Feb 09, 2011 12:05 pm

The 701c has a (soldered, 3V) CMOS battery AND a (rechargeable, 1.2V, removable) backup battery AND a main battery.
Them being from the last century, I would open the 701c up and inspect thoroughly for battery leakage and/or corrosion.

hjanzen · #3 Post by **hjanzen** » Wed Feb 09, 2011 1:20 pm

I appreciate your reaction but I thought I clearly mentioned the recent exchange of the soldered CMOS battery....
During that operation there was no indication of corrosion.

#4 Post by **RealBlackStuff** » Wed Feb 09, 2011 2:02 pm

I mentioned corrosion, because a 701c that I got in for repair, did not work because of it.

Errors 161/163 are for missing date/time. Replace the CMOS battery again...

hjanzen · #5 Post by **hjanzen** » Wed Feb 09, 2011 3:03 pm

In my above post I failed to mention that I replaced both batteries at the same time...

#6 Post by **RealBlackStuff** » Fri Feb 11, 2011 12:06 pm

We are not clairvoyant here...

hjanzen · #7 Post by **hjanzen** » Fri Feb 11, 2011 3:20 pm

You are quite right! Sorry..

I am afraid one of these days I have to dismantle the laptop again and check both batteries.
If I understand you well it is the one under the upper(sub) board that is keeping date and time and causing the 161 163 warning.

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