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You are here: MacNN Forums > Enthusiast Zone > Hardware Hacking > Making a Pismo PRAM Battery [Image Heavy]

Making a Pismo PRAM Battery [Image Heavy]
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Senior User
Join Date: Jun 2007
Location: Aberdeen, UK
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Apr 2, 2008, 03:41 PM
Having three dead Pismos in my possession, I initially thought about parting them out, but had no way to test the screens prior to sale. As a dead PRAM battery can stop an otherwise healthy Pismo from booting, replacing the PRAM battery might be a plan, just in case they are functional. However, they’re really quite expensive, so I’ve been trying to make my own.

Unfortunately, there seems to be nothing on the internet about how to do it—presumably, all the other Pismo owners facing this problem forked out for one. As such, I’m having to work on it from scratch. I pulled one of the PRAM batteries from one of the laptops, and dissected it. Photos of the battery are below:

The PRAM battery, pulled straight out of the machine.

The battery, with the cover removed. I did this by carefully slitting up the side in one of the grooves. As I suspected, it’s actually four smaller batteries inside. They read “Panasonic VL2330”. A bit of googling reveals that these are pretty standard button batteries. As such, I’m going to try and price some for my replacement unit—it may work out cheaper than buying a new PRAM.

Further images reveal that there are metal strips linking them into a circuit:

Now, this is all dependent on how much it would cost. Sadly, batteries like this are not cheap. However, something occurs to me: do all the batteries need to be new, or can I replace one and test it that way? My (limited) understanding of electronics leads me to believe that a single working battery would complete the circuit and supply power (albeit for a significantly lower span of time than all four). That seems the most cost-effective way to test them, allowing me to test them.

Any input is much appreciated! If I make any further discoveries, I’ll post them here.
Mac Elite
Join Date: Mar 2001
Location: München, Deutschland
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Nov 2, 2008, 03:23 PM
I'm reviving my Pismo at the moment (going sort of retro)

My PRAM battery is dead but th machine is working absolutely flawless. Could you read the specifications on the battery cells, my guess is these parts could be obtained cheaply via electronic parts stores. I recently got car fob batteries from the at 25% of the typical dealers' price.

Aut Caesar aut nihil.
Moderator Emeritus
Join Date: Apr 2005
Location: Cambridge, UK
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Nov 2, 2008, 05:44 PM
I reckon these are the same as standard CR2032 (common CMOS) batteries, just without the metal strips.

If they are the same thickness, there's no conceivable reason why you couldn't solder them together in the correct order and have a working pack again.

A colleague of mine did a similar thing to an older Compaq workstation, the CMOS battery had died. Compaq had a horrible habit of soldering them onto the motherboard. He snipped the old one off and soldered a new one on using some wires scavenged from a dead power supply unit. It wasn't pretty but it works.
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Nov 4, 2008, 05:38 PM
Seanc: No no no, this is a rechargeable Lithium Ion battery pack, not disposable batteries! Most Apple laptops have a rechargeable backup battery instead of disposable, since laptops are much more liable to be kept away from an outlet -- plus it's not just for PRAM, it's also to allow hot swapping (in sleep mode) of the main battery.

Koralatov: you absolutely do NOT want to replace just one cell. First of all, it may not work, second of all, it could be dangerous. (Lithium Ion cells are not to be f**cked around with!)

Honestly, why bother building it, when it costs less to buy it?!?
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Nov 4, 2008, 07:02 PM
Thanks for the heads up on that. I wasn't aware they were Li-Ion.
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Nov 7, 2008, 04:45 AM
So, each cell is 3 volts 50 mAh. It looks like they are wired to be two double power 3 volt pairs. 3 volts between the white and black wire, 6 volts between the red and black.

I wonder if there is a cheaper alternative to those VL2330 cells? The VL3032 is slightly larger but is 100 mAh so you'd only need two.

I have 2 Pismos and a Lombard- all with dead pram batteries. Dead main batteries too! They just stay at home plugged into their adapters.
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Apr 20, 2009, 01:37 PM
If you test the batteries individually, You will see two are dead (zero output) and two are still good (3V output)
I removed the the two dead batteries and reconnected the good batteries in the same order (3 volts between the white and black wire, 6 volts between the red and black.) and It works and it is holding charge.


If you have two sets of dead PRAM batteries, you can rebuild one good one

( Last edited by ICU2000; Apr 20, 2009 at 01:43 PM. )
Clinically Insane
Join Date: Dec 1999
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Apr 20, 2009, 04:32 PM
I'm sure Radio Shack has the part you're looking for for a measly $400.
"…I contend that we are both atheists. I just believe in one fewer god than
you do. When you understand why you dismiss all the other possible gods,
you will understand why I dismiss yours." - Stephen F. Roberts
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