Homebrew PRAM Batteries

[Trash80toHP_Mini]

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.

 

. . . 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]

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]

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]

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]

1 hour ago, joshc said:

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

 

Edited October 2, 2019 by ScutBoy

[jessenator]

1 hour ago, joshc said:

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  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]

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.

 

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. 

 

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]

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.

[johnklos]

8 hours ago, Stephen said:

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]

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

 

 

[cheesestraws]

15 hours ago, Stephen said:

Just found this thread and thought you might appreciate my solution

Oh, this is a very clean and neat approach.  I like it a lot.

[Stephen]

Thanks folks!

 

On 7/8/2020 at 7:48 PM, Crutch said:

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

 

 

 

if it works that's all that matters!

[mogs]

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.

 

 

 

[karrots]

On 8/10/2020 at 9:47 AM, mogs said:

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).

 

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

 

 

 

[Compgeke]

In a similar way, I've just straight up soldered CR2032 holders in place of the originals. Both Keystone #1058 and unknown SMT 2032 holders from Excess Solutions fit fine with the tabs directly over the original through holes. Flood through holes, glue holder in place, heat tabs. Works great. 

[anthon]

I designed this thing a couple years ago and was intending to sell them. I ordered 300 custom cable assemblies for it. It's designed so that the original mainboard can be preserved without modifiction, while re-locating the battery somewhere else (I was thinking outside the case). I never settled on a mounting / enclosure mechanism for the battery board. It uses two 3032s and a voltage regulator with very low quiescent current to provide 3.6v.