CMOS batteries - interchangeability **PIC**

[karotlopj]

Does anyone know if there exists a cross-reference of CMOS batteries against ThinkPad models?

Are they all basically the same apart from the connector?

[theterminator93]

From what I've seen the batteries themselves are always a flavor of lithium button cell - usually a CR2025 or CR2032. Those applications where the battery is shrink-wrapped and spot-welded to a pair of contacts and wires, it's still the same battery type inside the shrink wrap. I've rebuilt a few of those using 2032 cells in the past.

[RealBlackStuff]

Or CR2016.

[karotlopj]

What I was aiming to find out was how interoperable are the connectors.

Can't believe there are hundreds of different connectors.

Is it possible to solder connectors? Don't know how to spot weld...

[theterminator93]

Yes, it can be done. There are two, maybe three approaches that come to mind.

I've been known to pry off the metal contacts from dead batteries then solder them onto replacements. It's not ideal due to the heat involved - though the approach I use (a small dab of solder kept hot on the metal, then touched to a lightly-scratched surface of the battery and left to quickly cool) has yet to yield adverse effects.

Another option that is slightly less risky is to just splice the pigtails in place and shrink-tube the splices in the wire.

Finally, this one would be the cleanest but also least likely to work consistently, is to remove the contacts from the connector and reinsert them into the new connector. The pins can be released from them in most cases by depressing the small spring loaded clip on one side, then sliding the contact out. This would only work if the contacts between connectors are similar enough in size and shape, though.

[rkawakami]

About 11 years ago i posted this image:

(500x600; 38KB)

Two physically different connectors (600 series vs. the other two) and two different polarities using the same connector (T2x and X2x). Ignoring the much older systems which had a coin battery holder, I believe that all subsequent Thinkpads used one of these designs. Anyone correct me for systems newer than the T420/W520 since that's where my collection stops.

[m11k]

Interesting that the X2x series reversed the polarity.

I recently bought a bulk pack of so-called T4x CMOS batteries (https://www.ebay.com/itm/252964911921). These were compatible with my T60, X230, T430, and W530. The only issue I had was that they tended to have a little excess yellow plastic covering on them that made them not perfectly flat. I just carefully trimmed the end with a razor knife. On my 600X, which has a different connector, I did cut the wire off and solder on the cable from a dead battery. I also think the 600X takes a CR2025 instead of a CR2032, but the voltage is identical and they're similar enough in size that this didn't cause any problems.

One tip when testing CMOS batteries. Add a ~4.7K resistor load to the battery when measuring voltage (i.e. in parallel to the multimeter). These batteries can show a high voltage with no load, but if they are going dead it will drop off significantly when there is a load attached. I don't remember what voltages I was seeing for a good/bad battery, but I just compared the voltage measured (under load) on a brand new CR2032 vs the existing CMOS battery to determine whether or not it needed to be replaced.

[789]

Are they all basically the same apart from the connector?
Is it possible to solder connectors? Don't know how to spot weld...

I recently changed battery in a z60m. Purchased batteries in the dollar store. Carefully removed the plastic from the old batterry. Scratched the surface of the new battery, attached the wires, used electrical tape. It works.