Rebuilding Lombard/Pismo PRAM battery

[Byrd]

Hi,

As per my Conquests post, I've built up one "good" Lombard Powerbook G3 from two, which is specced as:

- 333 @ 433Mhz (did this once before, and it's rock solid yet again!), on the 400Mhz DVD-accelerated motherboard

- 384MB RAM/40GB 5400RPM HD

- OK battery, DVD drive

It's come up well, and running 10.4.11 quite nicely - good enough for Safari and Word, which is all it'll be used for by my friend.

The only other thing I need to tackle is to rebuild the PRAM battery, which is completely dead. If there isn't a good PRAM in a Lombard it tends to have some unusual behaviour when you plug it into mains.

I've stripped down one PRAM battery and found 4 x 3V Panasonic cells (Lithium? I can't tell, haven't check the part no yet) which appear to be soldered in parallel. Looking at how they're wired up it will be difficult to replicate this again, as it's hard to solder battery terminals - especially this many!

So I was wondering if there is a substitute single celled PRAM battery I could use, or if anyone has any other suggestions?

Also, I found this on LowEndMac:

I have resurrected supposedly "dead" PRAM batteries by connecting a Pismo to AC but with the main Li-Ion battery disconnected and the PRAM battery connected for between 24 and 48 hours nonstop, after which time the PRAM battery has been reactivated and recharged, enabling the Pismo to then be booted with the PRAM battery still connected.

I can't say it does much.

Thanks

JB

 

[wally]

...which is completely dead...

So see if one cell is shorted, eliminate it, then reconnect the remainder and try. Also, complete assemblies of unknown quality on eBay are a lot cheaper than new cells.

 

[Bunsen]

OR trawl Battery World and Jaycar for a higher capacity, single 3V lithium cell, small enough to tuck away somewhere inside

 

[Byrd]

Thanks all

I've two dead Lombard PRAM batteries here, so with luck I'll be able to make up one decent battery.

Jaycar sell a couple of potential replacement batteries too; one is a 3V 1400mah 3V lithium used for cameras (pretty big though), or a 575mah coin-type battery.

JB

 

[wally]

Cut the minimum number of straps midway needed to do a binary search. Cut where the spot welds allow you to have relatively long liftable stubs. Good cells should accept a brief test charge from a improvised trickle charge, like a 9V battery and a series 4.7 K ohm resistor, whereas a shorted cell will not budge from 0 volts, and indeed will measure low ohms with an ohmmeter. When soldering, lift the ends of the remaining strap stubs temporarily away from the cells, clean them and use small bridging wires and fast soldering technique as not to heat the cells much from the soldering operation...heat tends to make the cells unreliable. Do not try to solder directly to the cell surface. These are not as bad as the Lithium Ion technology, but they still do not like heat.