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DIY fix for Powerbook G4 (A1138) PRAM battery?

ybz90

macrumors 6502a
Original poster
Jul 10, 2009
609
2
Hello MR,

Long story short, I recently rediscovered my first computer (well, technically, second after an old, old beige Mac), a 15" hi-res PowerBook G4. It was predictably in pretty bad shape electronically (though aesthetically perfect except a minor corner dent) and I've been slowly and carefully rebuilding it.

I replaced some parts like the fans (redid the thermal paste too.. the factory job was embarrassing bad), cleaned up the internals and dust, got a cheapo aftermarket battery, maxed the RAM, and have a PATA SSD coming soon in the mail. The last thing though is the dead PRAM battery.

I was wondering if someone with more knowledge than I have could tell me if a PRAM battery from another model can be used with this one (mine is the A1138 model). Spares for my particular model seem to be inordinately expensive compared to previous ones...

Alternately, I am considering just replacing the actual battery itself on the circuit board. The main difference seems to be that with this final revision, Apple changed the design and layout of the PRAM battery circuit so instead of a circle battery, its some kind of rectangular packet. Does anyone know what kind of battery (or a compatible substitute) could be used?

Much thanks.
 

Lil Chillbil

macrumors 65816
Jan 30, 2012
1,322
96
California
Hello MR,

Long story short, I recently rediscovered my first computer (well, technically, second after an old, old beige Mac), a 15" hi-res PowerBook G4. It was predictably in pretty bad shape electronically (though aesthetically perfect except a minor corner dent) and I've been slowly and carefully rebuilding it.

I replaced some parts like the fans (redid the thermal paste too.. the factory job was embarrassing bad), cleaned up the internals and dust, got a cheapo aftermarket battery, maxed the RAM, and have a PATA SSD coming soon in the mail. The last thing though is the dead PRAM battery.

I was wondering if someone with more knowledge than I have could tell me if a PRAM battery from another model can be used with this one (mine is the A1138 model). Spares for my particular model seem to be inordinately expensive compared to previous ones...

Alternately, I am considering just replacing the actual battery itself on the circuit board. The main difference seems to be that with this final revision, Apple changed the design and layout of the PRAM battery circuit so instead of a circle battery, its some kind of rectangular packet. Does anyone know what kind of battery (or a compatible substitute) could be used?

Much thanks.

Sir, those models clock runs off of the main battery there is no pram
 

max¥¥

macrumors 6502a
Aug 7, 2008
640
29
Over there....
Hello MR,

Long story short, I recently rediscovered my first computer (well, technically, second after an old, old beige Mac), a 15" hi-res PowerBook G4. It was predictably in pretty bad shape electronically (though aesthetically perfect except a minor corner dent) and I've been slowly and carefully rebuilding it.

I replaced some parts like the fans (redid the thermal paste too.. the factory job was embarrassing bad), cleaned up the internals and dust, got a cheapo aftermarket battery, maxed the RAM, and have a PATA SSD coming soon in the mail. The last thing though is the dead PRAM battery.

I was wondering if someone with more knowledge than I have could tell me if a PRAM battery from another model can be used with this one (mine is the A1138 model). Spares for my particular model seem to be inordinately expensive compared to previous ones...

Alternately, I am considering just replacing the actual battery itself on the circuit board. The main difference seems to be that with this final revision, Apple changed the design and layout of the PRAM battery circuit so instead of a circle battery, its some kind of rectangular packet. Does anyone know what kind of battery (or a compatible substitute) could be used?

Much thanks.

i'm pretty sure the pbg4's use super capacitors for clock battries (at least mine does (i have a a1104)) so just leave it plugged in for a few hours
 

Brian Y

macrumors 68040
Oct 21, 2012
3,702
885
PowerBook G4s have "watch batteries".

If you have a later one, this will be a black rectangle connected to a USB board. If you peel back the black plastic, there are two watch batteries underneath which can be replaced.

 

Intell

macrumors P6
Jan 24, 2010
18,902
420
Inside
iBook's don't have a PRAM battery, but all Powerbook G4's do except for the 12" ones. Starting with the Powerbook G4 550Mhz/667Mhz model, they have rechargeable lithium coin batteries. These only start to charge after the main battery is fully charged or is removed. They have a much longer usable life that the main battery. They can die, but it is very rare. Typically, when replacing one, you should always replace it with the same model battery for maximum reliability and safety.
 
Last edited:

666sheep

macrumors 68040
Dec 7, 2009
3,626
232
Poland
Sir, those models clock runs off of the main battery there is no pram

Good joke, sir :D

Only one that does not have regular PRAM battery is 12" one.

And to the OP: while battery from A1106 may have that same specs as A1138 one, its board is different and most likely it won't work properly in A1138
 
Last edited:

ybz90

macrumors 6502a
Original poster
Jul 10, 2009
609
2
Thanks for the replies, I can confirm after teardown that the PRAM battery is like the one 666sheep linked to. Unfortunately, having sat uncharged for nearly three (maybe more?) years, this battery is as dead as a doorknob. I guess I'll just run it without the PRAM battery for the time being and use the main battery, and just keep my eyes peeled for a cheap used one.
 
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