• Hello, Guest! Welcome back, and be sure to check out this post for more info about the recent service interruption and migration.

Homebrew PRAM Batteries

register

Well-known member
all the pram batteries are removed from my computers(no battery = no leak)
Good point. One should consider to keep the battery on the outside of any machine that is not frequently cared for. Even recent battery makes have a tendency to leak when discharged (nasty corrosive stuff comes out). Simply attach the external battery connector or battery holder to the back panel of the computer (adhesive tape might do). For one machine I cut a piece of plastic into the size of the original PRAM battery and attched a wire to each end, so it serves as a plug to contact the battery holder without a change to the mainboard. In many cases you do not need to drill holes or apply any permanent changes at all.
Alternatively you could mount the battery pack into a plastic container that keeps the goo of some leaking batteries safely in place while leaving the outside appearance of your computer untouched.

 

onlyonemac

Well-known member
I once put a voltage regulator (built on a mini breadboard) in my mac. I powered it from a 9V PP3. It was terrible with bits of prestick and sticky tape amid wires running from end to end across the top of the hard drive :O ! But before that, it was worse. I had a small phone charger-style transformer and I used that to power the regulator and had to leave the case of the mac off 8-o !

 

register

Well-known member
How about using onlyonemac's suggestion and to combine the voltage regulator with the computers own PSU: tap some Volts through the voltage regulator to power the clock chip and add a delay circuit to power up the mainboard only a second later. Get the correct time from a time server and run an AppleScript programme to restore other PRAM based setting. In case of the P475 there are also instructions for an electronic circuit available to provide a soft power on (using the keyboard power button).

 

Trash80toHP_Mini

NIGHT STALKER
Getting back to the pics in the OP, I love the idea, but the holder appears to be overkill to this jackleg mechanic, engineer wannabe. [;)] ]'>

Suggestion for review & feedback:

00) Start with three inexpensive plain old alkaline batteries, IIRC, these have a longer shelf life and longer low current duty cycle than the expensive pink bunny variety . . .

01) use electrical tape to bind them together in the same config . . .

02) use electrical tape to "pressure wrap" the short inter-battery connections and long, color coded, leads in place . . . test . . .

03) wrap leads around pack for strain relief and secure with electrical tape so that the (twisted pair) leads project straight up from the side of the "top" battery as illustrated above . . . test . . .

04) wrap entire assembly in electrical tape to simplify the convoluted shape, maximizing volume/minimizing overall surface area . . .

05) do final testing . . .

06) hold the assembly by the leads and dip it into a can of "liquid rubber" tool grip or "liquid rubber" wire insulation to a depth of about an inch or so up the leads . . .

. . . either insulation material should be readily available at your local home improvement store, but the tool grip comes in pretty colors . . . [:eek:)] ]'>

07) crimp connect the assembly leads to the connector's leads . . .

08) secure assembly however and wherever you choose with the leads (the assembly's Achilles' heel in terms of leakage) pointing straight up.

Doing it this way is probably the least expensive way to do "leak-proof" insulated container battery packs for entire collections. Varying the battery combinations to suit each voltage requirement would be necessary, of course. The packs would be disposable, about as eco-friendly as I can imagine. Just cut 'em open to harvest the wires for re-cycling into another pack at the end of the alkaline cell's useful life.

No lead-free or any other kind of solder or soldering required!

If one of the cells fail/leak/burst/whatever, the elastic properties and the spare volume inherent in the "containment" design should come into play and save the day.

Whatcha think? :?:

 

register

Well-known member
For a leak proof assembly there needs to be a vent that allows gas from the battery to escape (avoid building up pressure in a sealed container), there needs to be some space or a getter inside the container to collect any liquid that may come out of the battery (probably a piece of toilet paper), and also it must be approved that the container is resistant to the ugly battery goo stuff, eating it's way towards precious electronics. Some polypropylene canister or bottle combined with the help of gravity could do, as long as the mounting position is chosen appropriately and the machine is stored in according position.

 

onlyonemac

Well-known member
...with the computers own PSU: tap some Volts through the voltage regulator to power the clock chip and add a delay circuit to power up the mainboard only a second later.
I know I wasn't asking for help but thanks for it anyway ;) . I had thought of hacking the computer's PSU, but I knew that the battery voltage had to be present before the main power could be applied. I didn't think of adding a delay to the main supply. You were thinking of a relay?

Having said that, however, I am now thinking of getting a proper PRAM battery :-/ , but good luck with your mac anyway.

 

Trash80toHP_Mini

NIGHT STALKER
For a leak proof assembly there needs to be a vent that allows gas from the battery to escape (avoid building up pressure in a sealed container) . . .
That's easy enough to do with my design, just add a piece of wire insulation from which the wire has been pulled into the twisted, color coded pair of leads.

Make it long enough and it could act as a drain to the outside of the case. ;D

. . . there needs to be some space or a getter inside the container to collect any liquid that may come out of the battery (probably a piece of toilet paper) . . .
No problem add the toilet paper pad underneath the two battery base during the initial binding wrap of of the the three cells. There's provision for plenty of extra space in between the batteries in the pack which is reserved by wrapping the assembly in order to minimize the surface area and simplify the topology of the pack.

Heck, wrap it enough times with electrical tape and you might be able to skip the tool dip altogether.

. . . it must be approved that the container is resistant to the ugly battery goo stuff, eating it's way towards precious electronics.
"Rubberized" tool grip liquid is both acid and oil resistant besides being non-conductive and fairly elastic. I'm sure the properties/makeup of the material is easily researched. Corrosion prevention shrouds for lead-acid battery terminals in cars appear to be made of the same or similar liquid -> solid phase change materials. The ones I've seen haven't appeared to be made by a casting process, but I'll take a closer look.

Dunno about the acid or oil resistance of liquid wire insulation, the purpose of that material is waterproofing spliced connections in outdoor, underground or interior wet space applications where shrink wrap isn't sufficient or won't work at all.

Some polypropylene canister or bottle combined with the help of gravity could do, as long as the mounting position is chosen appropriately and the machine is stored in according position.
PRAM batteries or packs should be removed for long term storage to begin with, they should at the very least be disconnected for medium term storage to preserve the charge anyway, so they may as well be removed entirely as well.

Barring catastrophic failure, any Homebrew PRAM Battery Pack will have ceased doing its job and should have been replaced long before the "normal" types of battery disintegration occur.

 

Gil

Well-known member
N00b question: What is the connector called that connects the battery to the pins on the logic board? I'd like to not splice wires if at all possible.

 

FacnyFreddy

Well-known member
I found that stacking cr2032 or similar cells, I can make my own replacement dc pack to get an old camera working.

An attempt to stack LR44 cells to come up with a pram battery was "mostly" successful. The power drain rendered it dead in less than a year.

Rechargable vl2330 cells are 3v and "might" be swapped out with mr2032, like with Logitech wireless/solar keyboards.

But the 2032 is a smaller diameter and 0.2mm thicker. YMMV

Getting my home made prams working was one of my reasons for not recycling or auctioning off a pair of powerbooks.

 

joshc

Well-known member
I once used a 3 battery holder and soldered the wires onto the existing cable from the old PRAM battery in a Power Mac 4400. I have a 5200CD which needs similar treatment.

I have 8 Macs at the moment (soon to be 9) - I have removed the PRAM batteries from all of them, I did order a pack of 5 new batteries but like others have said, it takes a lot to remember how long a battery has been in a given computer once you have more than a few of them.

It seems like there would be a market for someone out there to make replacement PRAM batteries ready to go for the Macs that use the connector pin style (those tend to be the ones where the batteries came in a plastic case, I think), maybe a nice side project for someone who has the time?

 

ScutBoy

Well-known member
I have 8 Macs at the moment (soon to be 9) - I have removed the PRAM batteries from all of them, I did order a pack of 5 new batteries but like others have said, it takes a lot to remember how long a battery has been in a given computer once you have more than a few of them.
That's why you write the replacement date on a piece of masking tape that you stick on the bottom of the machine. Or, a post-it note that you stick to the glass of the screen, which is easy to clean and can't leave a nice discolored spot you need to retrobrite out later :)

 
Last edited by a moderator:

jessenator

Well-known member
I once used a 3 battery holder and soldered the wires onto the existing cable from the old PRAM battery in a Power Mac 4400.
Tried this once and failed, only to later realize, "oh yeah, flux is a thing in soldering"… I might go back and actually make it work. I currently have one of the flat, square HarborFreight flashlights (not-so-neatly) cut apart as a battery tray and some industrial hook'n'loop holding it in place underneath the CD drive bracket. Gets the jorb done at any rate.

So far I just have a single half-AA that rotates with whatever machine I'm using, which solves my problem of accidentally setting-and-forgetting it in a machine not in use :lol:  also: I'm lazy and haven't gotten around to purchasing more, but… I'm also contemplating coin-battery replacement options for rest of the collection. I've seen a fair number of posts and videos showing it in action and in the long-term seems a tad more economical, although I don't know if I've mustered up enough chutzpah to work on a logic board again after my IIsi :/  

 

Compgeke

Well-known member
While not quit replacing the Rayovac bricks, these're "in the spirit" so to say. I've been playing with replacing the 1/2AA batteries with CR2032s in systems as a means of cutting costs. I can get a holder for ~$0.75 and a battery for $~0.40 in bulk, a lot cheaper than a $3-$5 battery. Even if they die faster, still cheaper than a 1/2AA. They also tend to be more resistant to leaking, but that's not to say they can't. They do tend to be less destructive if they do.

First one I did was a Mac IIsi. It's a bit hacky since I used a reclaimed battery holder made for through hole and it doesn't quite line up. From what I hear it hasn't died yet though - I didn't keep this machine.

UL12DsWl.jpg.370dfc088bb208d83fff25a04fff27df.jpg


Next system I tried it on was the Mac IIfx. 7 months later, it's still going fine, power on included. I did use some new holders though, Keystone surface mount ones. They more or less line up perfectly with the original pads, meaning you can tack them down with a little glue then solder like a surface mount device. 

H2iv7thl.jpg.78477c72d3a586541e7505132490cfbb.jpg


Some other systems I've done this two are a Macintosh IIci (power on circuit needs repairs, no idea if it's still working) and a PowerComputing Power 100. The Power 100 is still going fine, and it is one of the systems that needs a battery to turn on. Eventually I need to break out the Radius 81/110 and try it out too, I don't have any real batteries for it. I like to keep the real batteries in the special systems like the Daystar Genesis MP - boards I'd like to avoid doing rework on.

 

Stephen

Well-known member
Just found this thread and thought you might appreciate my solution (and tutorial). This solution allows you to neatly hook the fake battery to a real battery pack (e.g., 2xAA) and place the battery pack somewhere safer.

image.png

 

johnklos

Well-known member
Just found this thread and thought you might appreciate my solution (and tutorial). This solution allows you to neatly hook the fake battery to a real battery pack (e.g., 2xAA) and place the battery pack somewhere safer.
Very nice! If I had any Macs that I'd like to keep original, I'd definitely do that. Very clean :)

 

Crutch

Well-known member
Very nice. I did something similar here but just cut down a small piece of wooden dowel rod. Yours looks neater. Here’s mine:





9C45EB90-169D-4C9E-935A-E05E96826180.jpeg

8B504F34-474E-4E98-8906-2B0F226C7E5E.jpeg

451A8570-004B-479C-A42E-10BB315CD19A.jpeg

 

mogs

Member
Kia ora. This is my first post on this forum.

I thought this might be a good place to start, I've built a 2032 -> 1/2 AA adapter using veroboard and an appropriate holder. The metal terminals are made from solder lugs from 4mm "banana" sockets. But bits of terminal strip for 18650s would probably be cheaper.

Also what a PCB/product might look like, I would really like to have plated edges on this to remove the need for terminals. But I'm not confident of how to make sure that is fabricated correctly. It's also designed that it could be used as a drop-in replacement for the original holder (pads at the bottom have same pin spacing as 1/2 AA holder).

This is keeping time in my Q605.

pram.jpg

pram2.jpg

Pram3.PNG

 

karrots

Well-known member
Also what a PCB/product might look like, I would really like to have plated edges on this to remove the need for terminals. But I'm not confident of how to make sure that is fabricated correctly. It's also designed that it could be used as a drop-in replacement for the original holder (pads at the bottom have same pin spacing as 1/2 AA holder).

View attachment 36396
I like this idea. PCBWay has some information about edge plating on their website. https://www.pcbway.com/pcb_prototype/PCB_Sideplating.html

I went a slightly different way and made a battery holder replacement. Technically OSHPark doesn't do castellations but it works fine for the prototype need.

https://oshpark.com/shared_projects/rO2dGa2h

703b1de4a48b0b653010103db09f9144.jpeg.f6993b0a607c71c4aac851c37bdda3e2.jpeg


 
Top