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    Capacitors instead of RTC/CMOS batteries

    Hi, would there be somekind of knowledgebase for laptops, that are using capacitors (+laptop battery) instead of RTC/CMOS batteries for keeping BIOS/UEFI values "alive/stored"?

    I learned hp and lenovo are doing this on their newer models a lot. I myself have a 2016 ASUS X540L here, that has not RTC/BIOS battery.

    Id like to know what to look for on the mainboards.
    Thank you in advance.
  • Answer selected by STKR123 at 08-30-2024, 10:55 AM.

    bios settings are in flash,
    the rtc is built into the bridge chip and probably powered by a lithium rechargeable battery soldered to the board.
    super-capacitors as they are called are shit - companies tried them and mostly dropped the idea.

    Comment


      #2
      bios settings are in flash,
      the rtc is built into the bridge chip and probably powered by a lithium rechargeable battery soldered to the board.
      super-capacitors as they are called are shit - companies tried them and mostly dropped the idea.

      Comment


        #3
        Ah, "super capacitor".
        Now I found some more things to consider and to read.

        https://www.badcaps.net/forum/genera...uper-capacitor

        Thank you!

        Comment


          #4
          Stj just said it. While I do have some success with large super capacitors, the small one are a pain in the rear. If you want you can read my Fluke 289:super capacitor thread. That is one device for example where the manufacturer went from super caps to battery.

          Comment


            #5
            Super caps are good when they need to provide power for a short time [seconds, maybe minutes], such as in a dash cam after the ignition is turned off.

            They need to power it long enough to close files and do an orderly shutdown -- which shouldn't take more than a couple of seconds. Unlike batteries, their capacity won't change much, so they're a better option in that particular use.

            Comment


              #6
              they leak - they have no safe use

              Comment


                #7
                The original Xbox used a supercap. It was a 2.5v 1F cap and they are prone to failure. As long as the xbox was connected to mains, it would keep the cap charged and maintain the date/time. They expected that this would be the case as most people just leave their consoles plugged in all the time. In the event it was unplugged or there was a power failure, the cap would last a few hours or so before completely discharging.

                Comment


                  #8
                  Originally posted by stj View Post
                  they leak - they have no safe use
                  Evidence please showing that this is a widespread issue.

                  Comment


                    #9
                    Originally posted by aurgathor View Post

                    Evidence please showing that this is a widespread issue.
                    That's true for the small supercaps. The big ones do not have that leaking problem. I am running an experiment using large supercaps (two 25F in series) and with a solar panel and some device for 8 years now and all is good. The small supercaps just keep looking at the fluke 289 thread.

                    Comment


                      #10
                      I have used the lager super cap before with out any issues but I was not aware of issues with the smaller version of them because I used one in a project for a company that had a storage tank for sanding blasting material and wanted to how much material was in the storage tank I used it for a memory retention time chip and I tested it several times for several hours and retained it memory

                      I no longer work for this company anymore but the last time I talked to a person who used to work there a couple years later said that they were still using so who knows now if it is still working or not this was over 15 years ago
                      9 PC LCD Monitor
                      6 LCD Flat Screen TV
                      30 Desk Top Switching Power Supply
                      10 Battery Charger Switching Power Supply for Power Tool
                      6 18v Lithium Battery Power Boards for Tool Battery Packs
                      1 XBox 360 Switching Power Supply and M Board
                      25 Servo Drives 220/460 3 Phase
                      6 De-soldering Station Switching Power Supply 1 Power Supply
                      1 Dell Mother Board
                      15 Computer Power Supply
                      1 HP Printer Supply & Control Board * lighting finished it *

                      These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%
                      1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                      2 Hem Saw Computer Stack Board
                      All of these had CAPs POOF
                      All of the mosfet that are taken out by bad caps

                      Comment


                        #11
                        Originally posted by CapLeaker View Post

                        That's true for the small supercaps. The big ones do not have that leaking problem. I am running an experiment using large supercaps (two 25F in series) and with a solar panel and some device for 8 years now and all is good. The small supercaps just keep looking at the fluke 289 thread.
                        To me that looks like *one* bad cap in one particular product. Or in the XBOX, but I have not seen any indication that this is a widespread issue. I do know that with regular caps, certain years from certain manufacturers can leak, but that doesn't apply to all caps. I have at least a couple of devices (i.e. dash cam) with a supercap, and had zero issue with them. I know that's a very small sample size, but on the other hand I've had bad cap issues with probably over 2 dozen pieces of equipment over the years.

                        Comment


                          #12
                          Originally posted by aurgathor View Post

                          To me that looks like *one* bad cap in one particular product. Or in the XBOX, but I have not seen any indication that this is a widespread issue. I do know that with regular caps, certain years from certain manufacturers can leak, but that doesn't apply to all caps. I have at least a couple of devices (i.e. dash cam) with a supercap, and had zero issue with them. I know that's a very small sample size, but on the other hand I've had bad cap issues with probably over 2 dozen pieces of equipment over the years.
                          It's similar to regular capacitors. Little ones are usually they go bad and the big ones are better and last. How long, I have no idea.
                          For example: My first CFL bulb I bought 22 years ago, is still working, while most CFL bulbs is the house went dead and got replaced for LED. I still got one 19 year old incandescent bulb running. Some things run longer than others, even so it is the same product.

                          Comment


                            #13
                            they leak in sega arcade equipment leading to trace repairs
                            they used to leak in vrc's but it was a minor issue because they used single-sided boards.
                            the only ones that didnt leak were the old ELNA ones that were in thick steel cans - they probably knew something!

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