Thinkpads Forum

When I first got my 600x, the cmos was dead.
I replaced it with a brand new cr2035, and it worked fine.
Now, it seems that whenever I have it unpluged for more than a few moments, the date and time reset


Is the 600x known to go through the cmos batteries so quickly like that? It couldn't have been more than 6 months since I got it..

If your main battery is dead, and AC is disconnected, then yes a weak CMOS battery will not last very long. Do you have any way of telling how old your "new" CMOS battery is?

Neil wrote:If your main battery is dead, and AC is disconnected, then yes a weak CMOS battery will not last very long. Do you have any way of telling how old your "new" CMOS battery is?

Well, I bought it at a drugstore before I put it in..

I do not have a main battery at all for the machine. I hallowed out the battery pack so now it is am empty shell to put things in.

wkw wrote:Well, I bought it at a drugstore before I put it in..

That implies you either taped the wires to the battery or soldered them on. Either method has problems. Tape can loosen and interrupt the connection of the battery to the motherboard. Soldering (if you were able to get the wires to stick on the smooth surface of the battery) will drastically heat up the battery and could have damaged it (i.e., shortened its life). You also dodged a bullet as excessive heat can make the battery explode.

The best way to determine if the battery is the problem would be to measure the voltage with a meter. A "new-ish" CR20xx battery should be 3V. Anything less than 2.7V should be replaced.

Other possibilities:

- The "new" battery from the drugstore was sitting on the shelf for a long time and was mostly dead (ref. Princess Bride )
- There's an excessive amount of current being drawn by the motherboard's circuits from the CMOS battery; a short or low resistance path will drain the battery

How would you suggest I replace the cmos in the future?
I have two other, old and dead cmos from two other 600x..

Use the proper CMOS battery that already has the leads and connector welded onto the battery. You can find them on eBay for only a few dollars. It's best to search for them by including the official IBM part number. Something like: battery thinkpad 02K6502

If you need more than one, it helps to look through the eBay search results and find a seller that offers a discount on multiple units. Here's a totally random sample from a search I just did (limited to US sellers): http://www.ebay.com/itm/110774035771 Note that I'm not affiliated with this seller at all. I would also suggest you obtain / borrow a multimeter and verify that the voltage is at least 3.0V when you first get them.

I have an anologue multimeter, so I guess I can test the voltage in the battery I am using currently.