Does keeping a Powermac plugged in keep the battery last longer?

Discussion in 'PowerPC Macs' started by poiihy, Mar 8, 2015.

  1. poiihy macrumors 68020

    poiihy

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    #1
    If a PowerMac is left plugged into the wall, would the PRAM battery last longer? I would think so, because the PRAM would be powered from the power supply instead of battery.
     
  2. Intell macrumors P6

    Intell

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  3. bunnspecial macrumors 603

    bunnspecial

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    #3
    Within reason, I've found that having a computer plugged in for an extended period of time will seemingly recharge the battery.

    I'm basing this on experience with two computers:

    1. My iMac G4 had a dead battery, and I had it plugged in and powered on for probably 4 months. A month or two back, I powered it down and unplugged it for 15-20 minutes to borrow the power cord. It held time while I had it powered down.

    2. My dual 1ghz Quicksilver was plugged in and pretty much continuously powered on from July 2014 to February 2015. Before that, I had it plugged in sporadically, and it would always lose time. I unplugged it to swap it out for a replacement dual 1ghz I bought back in February. The computer sat unplugged for about a week. When I powered it back on, the time was still correct. On this particular computer, I'd removed the WiFi card, so I'm positive it wasn't just simply that the time reset before I noticed.
     
  4. Intell macrumors P6

    Intell

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    #4
    The PRAM batteries used in PowerMacs are not rechargeable nor does the logicboard provide power to the battery terminals when the machine is plugged in.
     
  5. bunnspecial macrumors 603

    bunnspecial

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    #5
    All I can do is repeat my experience, although I realize it's anecdotal...

    Is it possible that there was a capacitor in the PSU holding enough residual power to keep the clock going in my cases?
     
  6. Intell macrumors P6

    Intell

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    #6
    There are capacitors in the power supply that can maintain the clock. How long it can depends on the age of the capacitors and the model of the machine.
     
  7. MatthewLTL macrumors 68000

    MatthewLTL

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    #7
    My Macs lose time and date the second the power cord is unplugged... spite the fact i bought a brand new battery for the eMac a week after i bought it it was dead a few months later.... Any reason why Mac OS X falls back to 12/6/1969? Macs let alone the computers we know today didn't even exist back then!
     
  8. poiihy thread starter macrumors 68020

    poiihy

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    #8
    Huh very interesting; so then I should keep the DA plugged in instead of unplugging it all the time.
     
  9. MagicBoy macrumors 68040

    MagicBoy

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    #9
    It's Unix related - the time/date format counts the number of seconds elapsed from 1st January 1970.

    Hence why a bad PRAM battery resets the clock to zero.
     
  10. mikiotty macrumors 6502

    mikiotty

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    #10
    You may have enabled the "Set date & time automatically" option in System Preferences. If yes, your Mac did set the time from the web during the boot process, and you didn't notice it had lost it because of that. Happened with my G5 every day as I unplugged the machine every day and had no PRAM battery. :p
     
  11. bunnspecial macrumors 603

    bunnspecial

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    #11
    As I said, there was no internet connection at the time. No airport card and no Ethernet.
     
  12. mikiotty macrumors 6502

    mikiotty

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    #12
    Whoops, didn't read it. Sorry :D
    BTW, the same thing happened on my iMac G5. Lost date and time the first time I powered it up after about a year, kept them later. Strange things happen in these old Macs... :p
     
  13. MatthewLTL macrumors 68000

    MatthewLTL

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    #13
    not the case. With my MDD even though i have it selected to set time and date automatically i ONLY does it when i open up the time and date settings
     
  14. ziggy29 macrumors 6502

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    #14
    Even so, 12/6/1969? Usually (at least in the Americas), it would reset to 12/31/1969, not 12/6/1969, anywhere from about 3-7 PM. As you correctly stated, Mac OS X is Unix-based, and the "beginning of time" for Unix is January 1, 1970, at 12:00 midnight GMT. So if you are in (say) US Pacific Time, 8 hours behind GMT, a reboot with a dead PRAM battery would start up showing 12/31/1969 at 4 PM until an automatic network reset of time and date fixed it.

    And as an aside, until the migration from 32-bit Unix to 64-bit Unix took hold, Unix had a "Y2.038K problem" -- basically, the number of seconds from the "Unix Big Bang" (1/1/1970) until the overflow of a 32-bit time register would occur in 2038. Thankfully, pretty much all critical Unix-based systems are at least on 64-bit time now, and won't suffer this problem for a very long time.
     
  15. MatthewLTL macrumors 68000

    MatthewLTL

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    #15
    Date sets to 12/31/1969 my mistake sorry
     
  16. Intell macrumors P6

    Intell

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    #16
    I believe the reason some Macs reset to just before the beginning of epoch is that the programmer of OpenFirmware or someone else's birthday is that time.
     
  17. MatthewLTL macrumors 68000

    MatthewLTL

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    #17
    isnt OF only used by apple?
     
  18. Intell macrumors P6

    Intell

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    #18
    No, it was made by Sun and used in some of their Sun workstations and servers.
     
  19. MagicBoy macrumors 68040

    MagicBoy

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    #19

    Good question. I can't say I've seen a PPC Mac with a dead PRAM battery show anything other than 1970 by the time I've got into OS X to correct the date. Might be an firmware thing?
     
  20. MatthewLTL macrumors 68000

    MatthewLTL

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    #20
    So curiousity strikes again... Why did apple decide to use OpenFirmware instead of a BIOS?
     
  21. Intell macrumors P6

    Intell

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    #21
    It's more flexible and powerful than the standard and rigid BIOS.
     
  22. MatthewLTL macrumors 68000

    MatthewLTL

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    #22
    how so? and if that is the case why dont PCs use it?
     
  23. Intell macrumors P6

    Intell

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    #23
    I suggest using a search engine to further your knowledge on that subject.
     
  24. jackperez, Apr 22, 2015
    Last edited: May 4, 2015

    jackperez macrumors newbie

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    #24
    poiihy, it is very important to note that the PRAM battery cannot be recharged, it is not rechargeable and secondly there are no lines that can recharge it and keep it working that the same time. Please know that any battery which has just two terminals cannot be recharged and used at the same time. Since the battery has to keep time at all times and it requires minimal power which the said battery can provide for decades, the designers don’t emphasize on making it rechargeable.

    pcb cost
     
  25. Intell macrumors P6

    Intell

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    #25
    The PRAM battery is not used to constantly keep the time. It is used only when the power cord for the machine is unplugged or the power supply is not getting power. When the cord is connected and the power supply is energized, the trickle power keeps the clock running. In a properly operating PowerPC Mac with the little cylindrical battery, the PRAM battery will maintain the clock and other PRAM settings for about 3-5 years if the machine is unplugged for the entirety of the battery's life.
     

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