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PRAM battery; mains off/on?

Message #1 - Posted 2006/09/02 - PeterG

Extract from a mac book, "It (refers to PRAM battery) keeps a small portion of memory ... ticking over with the basics about your Mac's setup when there's no power connection. If you leave your Mac unplugged for any length of time this battery can be rundown" [I know about date time etc.]

My question is this, " How does mains power affect the PRAM battery i.e., keep it charged? IIRC, in my experience it is NOT a rechargeable battery! --
Regards

PeterG. (aka Lobo)

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Message #2 - Posted 2006/09/02 - Peter Ceresole

PeterG wrote:

My question is this, " How does mains power affect the PRAM battery i.e., keep it charged? IIRC, in my experience it is NOT a rechargeable battery!

I believe it just prevents it running down. As you say, it doesn't actually charge it, just prevents discharge.

Peter

Message #3 - Posted 2006/09/02 - PeterG

On Sat, 2 Sep 2006 15:44:44 +0100, Peter Ceresole scribbled by his own authority...
(in a previous article):

PeterG wrote:

My question is this, " How does mains power affect the PRAM battery i.e., keep it charged? IIRC, in my experience it is NOT a rechargeable battery!

I believe it just prevents it running down. As you say, it doesn't actually charge it, just prevents discharge.

As an afterthought, I presume the live mains into the computer -although computer not switch on- somehow retain the computer settings and, it is only where there is no mains power then the PRAM battery takes over.

Maybe someone knows different.

Regards

PeterG. (aka Lobo)

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Message #4 - Posted 2006/09/02 - D.M. Procida

PeterG wrote:

Extract from a mac book, "It (refers to PRAM battery) keeps a small portion of memory ... ticking over with the basics about your Mac's setup when there's no power connection. If you leave your Mac unplugged for any length of time this battery can be rundown" [I know about date time etc.]

My question is this, " How does mains power affect the PRAM battery i.e., keep it charged? IIRC, in my experience it is NOT a rechargeable battery!

It doesn't keep it charged, but if there is mains power then the battery isn't required to give up its juice to keep things ticking over.

Daniele

Message #5 - Posted 2006/09/03 - PeterG

On Sat, 2 Sep 2006 16:09:04 +0100, D.M. Procida scribbled by his own authority...
(in a previous article):

PeterG wrote:

Extract from a mac book, "It (refers to PRAM battery) keeps a small portion of memory ... ticking over with the basics about your Mac's setup when there's no power connection. If you leave your Mac unplugged for any length of time this battery can be rundown" [I know about date time etc.]

My question is this, " How does mains power affect the PRAM battery i.e., keep it charged? IIRC, in my experience it is NOT a rechargeable battery!

It doesn't keep it charged, but if there is mains power then the battery isn't required to give up its juice to keep things ticking over.

Daniele

Got that bit. What I'm trying to establish is...

..if the computer on/off button is OFF but the mains lead connected and ON, what is saving the PRAM? Is it the mains connection -even although the computer is not fired up or is it the battery?

My friend's iMac (OS 8.5) appears to be what one would think are the PRAM battery symptoms (date and clock are OK) and other time is seems OK. So, I'm trying to establish exactly how the PRAM functions before I look deeper

I have rebuilt the desktop; reset the PRAM; run Norton; defraged; checked with Techtool Pro. About to get the startup disk and try DiskWarrior.

May be loose RAM module?

Regards

PeterG. (aka Lobo)

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Message #6 - Posted 2006/09/03 - D.M. Procida

PeterG wrote:

Got that bit. What I'm trying to establish is...

..if the computer on/off button is OFF but the mains lead connected and ON, what is saving the PRAM? Is it the mains connection -even although the computer is not fired up or is it the battery?

There is always a 5V trickle from the PSU for just this, amongst other things.

Daniele

Message #7 - Posted 2006/09/03 - PeterG

On Sun, 3 Sep 2006 11:10:21 +0100, D.M. Procida scribbled by his own authority...
(in a previous article):

Got that bit. What I'm trying to establish is...

..if the computer on/off button is OFF but the mains lead connected and ON, what is saving the PRAM? Is it the mains connection -even although the computer is not fired up or is it the battery?

There is always a 5V trickle from the PSU for just this, amongst other

things.

Daniele

Thanks Daniele that's what I wanted to know. I now suspect the problem to be the computer being switched off at the mains for days (week?) at a time.

Regards

PeterG. (aka Lobo)

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Message #8 - Posted 2006/09/03 - Peter Ceresole

PeterG wrote:

Thanks Daniele that's what I wanted to know. I now suspect the problem to be the computer being switched off at the mains for days (week?) at a time.

Yes, that would do it. I had a beige G3/266 that refused to start after it had been switched off at the mains, over the holidays. Replacing the PRAM battery fixed that...

Peter

Message #9 - Posted 2006/09/05 - Chris Ridd

On 2006-09-03 11:10:21 +0100, D.M. Procida said:

PeterG wrote:

Got that bit. What I'm trying to establish is...

..if the computer on/off button is OFF but the mains lead connected and ON, what is saving the PRAM? Is it the mains connection -even although the computer is not fired up or is it the battery?

There is always a 5V trickle from the PSU for just this, amongst other things.

I hope that's a trickle of current, and not voltage ;-)

Cheers,

Chris

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