• CMOS Battery Wiring Question

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    Does the difference between the order of the wires on the original CMOS battery connector and the order of the wiring pattern on the replacement battery connector matter?

    I installed the replacement CMOS battery, but the laptop still loses the date and time.  I figure that means either the replacement battery is bad, or the difference in the order of the wires on the replacement battery connector matters. That is why I am asking about this.










    • This topic was modified 1 year, 4 months ago by kc27.
    • This topic was modified 1 year, 4 months ago by kc27. Reason: Add more details
    Viewing 11 reply threads
    • #2418482

      The wiring of the color coded wires does matter.

    • #2418474

      The wires must match the color of the wire of the old battery. The red and white must be changed to match the original battery

    • #2418484

      I am glad you included the picture. It sounded like you were asking if the polarity of the battery matters, and yes, <span style=”text-decoration: underline;”>of course</span> it does – isn’t that obvious? But with your picture, I see the confusion – and why it is not so obvious; the red and white wires are reversed.

      I am confused as to why there are even 3 wires – there are only 2 poles on a battery, the Positive and Negative poles. With the original and the red in the middle, that might be used for reverse polarity protection. But with a keyed connector (where it can only go in one that), that is not needed.

      You are going to have some how determine how those wires are attached. If handy with a multimeter, you could do it that way. But I suspect you may need to cut open the blue insulating wrap to inspect the batteries to see how the wires are attached, then rewire the replacement to match. Most likely, the red is to positive, and needs to be swapped (cut, swapped, then spliced) with the white.




      Bill (AFE7Ret)
      Freedom isn't free!

    • #2418497

      I ran into the same problem when replacing an old ThinkPad CMOS battery about 5 yrs ago. I couldn’t believe it and had to check several laptops to confirm, but I was surprised to discover not all ThinkPad models used the same CMOS battery pinout, despite using the exact same connectors.

      The metal crimp-on connectors are a snap-in fit inside the plastic holder, so I cinched the plastic end in a small desk vise, used a magnifying glass and sewing needle to depress the metal latches, slid the wires+connectors out, and snapped them back in, in the proper color-coded order. The battery worked perfectly after that.


    • #2418554

      Wire colour is not an indicator of correct orientation. If you change the wires around you may damage your PC / the battery, or not, per dg1261’s post.

      Can you ask the battery supplier?

      cheers, Paul

    • #2418570

      You can see the battery ends are right – note the rounded edge is the side with the negative end of the battery. confirm with a meter if needs be (red should be 3V WRT black and white). I assume as you say it doesn’t fix the problem that it plugs in, so all you really need to do is ensure when you plug it in the colours of the wires still attach to the main board in the same order with the replacement battery even if the connector isn’t quite the right one.

      The connectors are likely JST but the Molex one with flatter pins makes a better picture to put the detail on. I suspect you need to swap the white and red wires on the replacement I suspect. use a hat pin, small precision screwdriver, or similar pointed prove – insert, lift the tab and use the tip of the probe under the tab to hold it whilst withdrawing the wire. press the tab down with the problem to level it with the housing so the new wire locks when you push it in (note the side of the metal connector  with the “gap” goes to the tab..)

      If it doesn’t work, the attempt seems likely to have killed the battery as the red wire was connected to a pin where a negative connection would normally be – I suspect the “loop” of white and black to the same terminal visible in the photo (which are likely joined) performs the function of the battery jumper on a desktop system to ensure a reset to clear any corrupt data when the battery is changed.

    • #2418573

      Prove and problem should both be probe where they don’t make sense! I should really read the whole thing when fixing my typos..

    • #2418586

      The order of the colored wires are the same where connected to the battery:

      Red – pos side

      Black and White – neg side

      Therefore the connecting order to the mother board must be the same.  The red and white wires need to be switched.

      The third wire is used to monitor the battery – if that function exists on the current motherboard.

      HTH, Dana:))

      HTH, Dana:))

    • #2418718

      That appears to be correct.

    • #2418769

      Go to Parts people: The Dell experts since 2002. Dell OEM Replacement Parts.
      Enter Dell’s Service Tag and order the original CMOS battery for your Dell Precision M6500.

      HP EliteBook 8540w laptop Windows 10 Pro (x64)

    • #2418984

      Drcard:)) was correct, the black and white wires are tied together – see photo below. I did try parts-people.com as cmptrgy suggested, they do not have any batteries in stock. I do not have the visual acuity to do the pin swap that dg1261 and oldguy suggested.

      I  did not pay attention to the order of the wires when I purchased the first replacement battery. I bought a second battery with the wires in the correct order and that solved the problem. I have purchased this type of battery in the past for other units, I must have just gotten lucky and bought compatible batteries by chance because I never checked the wire order before purchasing a CMOS battery in the past. This is the first time the order of the wires was an issue.

      Thanks for all the help on this, what should have been an easy fix.




      1 user thanked author for this post.
    • #2422718

      Amazing!  I have exactly the same problem on the identical machine.

      Thank you to the OP and all subsequent posters.

      Why would you make (and specify) two batteries with identical 3-wire connectors, but opposite polarities at the connector end???  (What could possibly go wrong?)

      At least the designers were clever enough to incorporate protection against incorrect polarity — after resetting the CMOS with the correct connections, the computer seems unharmed.

      — AWRon


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