Forum Rules and Etiquette

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Rule 5: Copyright and other legal issues

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CMOS Battery Restoration

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    CMOS Battery Restoration

    I got a 486 Dell Latitude XP 4100C off of Craigslist, of course the CMOS battery is dead, but so far I haven't found any place online where I can get a replacement.


    The battery itself is just a strung together set of flat Ni-Cd batteries - I'm wondering if anyone on this site has just tried to open one of these up and replace the individual Ni-Cd batteries...?

    Are there any other options for replacing this battery?

    Thanks for your help.

    You can get a 4 AA or 4 AAA holder and use that.

    Like this:

    or this:
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step


      [QUOTE=Stone;284287]You can get a 4 AA or 4 AAA holder and use that.

      Nice, ok. The only thing is the specific voltage and amperage of this battery. It's a model 6GB60-FP, 7.2 V and 60 mAh

      The AA and AAA holders wouldn't match that right...


        Originally posted by Stone View Post
        I think he might have a hard time cramming one of those in a Laptop Case.

        OP Have you tried calling Batteries Plus? There web site indicates they may have compatable battery but no details.


          Why not just buy one?
          Reach me: vcfblackhole _at_ protonmail dot com.


            Originally posted by ibmapc View Post
            I think he might have a hard time cramming one of those in a Laptop Case.
            Good point. I had desktop in my head.
            PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step


              Ok thanks for the helpful replies.

              I don't know much about these CMOS batteries - is it possible to use a 7.2 V battery that has a different mAh rating? The original battery I have is 7.2 V and 60 mAh. The link Chuck(G) gave me above is for a 20 mAh battery...

              Can I do any damage to the CMOS if I plug in the wrong battery type?


                Also, thought I'd post a few interesting things about batteries I just learned:

                Connecting a series of batteries in parallel (all + connected together, and all - connected together) will have the same voltage as one cell, but the current will be multiplied by the number of batteries you have.

                Connecting a series of batteries in serial (the + of the first is connected to the - of the second, and so on) will multiply the voltage by the number of batteries you have, but the current will be the same as one cell.

                So since I can see 6 batteries in the CMOS battery I pulled out of the laptop, they are probably 1.2 V 60 mAh batteries wired in a serial pattern.

                Maybe I could just buy separate batteries and piece them together to get 7.2V at 60 mAh. Does anyone have any experience with this?


                  When it comes to batteries only the Volts are crittical. Too many Volts can fry the circuit. Amps don't matter, as long as you have enough. The circuit will only draw the Amps it requires. So the 20 mAh battery Chuck referenced is fine. You don't think Chuck would steer you wrong, do you?
                  PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step


                    Ok awesome, thanks for the help.

                    This goes along with what I've read online - the Voltage is what matters. The components will only draw the current they need.

                    I don't know Chuck, I'm pretty new to this site - but from now on I won't suspect he'd steer me wrong.

                    Thanks again.


                      The clock chip when running from the standby supply consumes microamperes. Take a look at the datasheet for the MC146818, which just about alll PC CMOS clock-configuration chips are based on. 50 microamps on standby. At that consumption a 20mAh charge would last 20000/50 = 400 hours before needing a recharge (it's actually much longer than that because the CMOS clock will continue to work down to about 2.2V)
                      Reach me: vcfblackhole _at_ protonmail dot com.



                        This one is in the US and $3.37 shipped.

                        Name brand CMOS laptop batteries are cheap on ebay
                        What I collect: 68K/Early PPC Mac, DOS/Win 3.1 era machines, Amiga/ST, C64/128
                        Nubus/ISA/VLB/MCA/EISA cards of all types
                        Boxed apps and games for the above systems
                        Analog video capture cards/software and complete systems