Thread

LCII PRAM Battery

68kMLA Hardware 11 posts Dec 3, 2007 to Jun 24, 2008

#1 Mon, 3 Dec 2007 - 04:59 68kMLA

Does anyone know what the voltage of the PRAM Battery in an LCII is?

Is it possible to emulate it with AA(s)? Thanks!

#2 Mon, 3 Dec 2007 - 05:09 68kMLA

3.6s. You can hook up 2AAs and wire it up, usually it's sufficient. I've never done it, but others have.

#3 Mon, 3 Dec 2007 - 10:38 68kMLA

It's the standard half-AA battery.

A LC2 will NOT work without one or with a low-voltage one. Believe me, I know this from experience.

What mine did was something like this:

Turn on.

Wait for about 30 seconds, booting normally.

Bong and reboot.

Bong and reboot.

Bong and reboot.

As far as I know, it wouldn't stop ever if I left it on. Any further hard-resets would cause it to go straight to the bong-reboot cycle.

NOTE: When replacing the battery, take the old one out and leave it overnight(or 2 nights) and then put the new one in and leave that overnight. Then you can boot.

#4 Mon, 3 Dec 2007 - 10:55 68kMLA

3.0V from 2 x 1.5V is borderline for any Mac that needs a 3.6V battery. 3.3V should be the think-twice point, and 2.8V is already the chuckaway point. There are Macs that boot better without any battery at all rather than a sick battery. Others will not boot at all when the battery is in the range 2.8 to 0.0V. Amongst other things, it depends which parameters are stored in the PRAM of the Mac in question, and how critical they are for startup. 3.6V batteries can be had for USD4 each, plus postage, from the eBay seller ronaldo101. Why muck about with anything else?

de

#5 Mon, 3 Dec 2007 - 20:34 68kMLA

A LC2 will NOT work without one or with a low-voltage one. Believe me, I know this from experience.

Mine has never had one, yet used to always work without one, with no problems like having to double-boot. It stopped working recently and just comes on with no chime, a little bit of disk accessing and then nothing, just the fan spinning and no display, but I think that must be capacitor leakage rather than the battery as it always worked fine without the battery.

#6 Mon, 3 Dec 2007 - 21:38 68kMLA

2 x AAs will work as will a single, 3 Volt coin cell, instead of the usual 1/2 AA battery. However, for peace of mind you're best buying the proper 3.6V 1/2 AA battery. RadioShack stocks them in the US I believe and they are often available from other places and eBay sellers (in the UK anyway).

#7 Mon, 3 Dec 2007 - 22:40 68kMLA

chris: You could boot it, wait for the first Bong, then turn it off then on again quickly. Slow enough so the PSU shuts off, but still kinda fast. Then it should boot normally.

#8 Mon, 3 Dec 2007 - 23:49 68kMLA

3x1.2 V rechargeable batteries might work. Gives you the exact 3.6 V and when the Mac starts forgetting the time, pop the batteries in the charger overnight.

#9 Tue, 4 Dec 2007 - 00:06 68kMLA

Patrikool: That was one of the things I tried. Several times.

Replacing the PRAM battery with a new one was the only thing that worked.

#10 Tue, 24 Jun 2008 - 19:20 68kMLA

2 x AAs will work as will a single, 3 Volt coin cell, instead of the usual 1/2 AA battery. However, for peace of mind you're best buying the proper 3.6V 1/2 AA battery. RadioShack stocks them in the US I believe and they are often available from other places and eBay sellers (in the UK anyway).

The only problem with RadioShack is that they want $20 for this particular battery. I'd only buy from them if I were desperate.

-lee

#11 Tue, 24 Jun 2008 - 21:30 68kMLA

Talk about inflation! I bought one since I needed it ASAP five years ago for $12 there.