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Homebrew PRAM Batteries


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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.

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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.

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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?

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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 by ScutBoy
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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 :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 :/ 

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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

 

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

 

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.

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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.bacb10b8b33c3221d3826ade1383934c.png

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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 :)

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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:

 

 

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

 

if it works that's all that matters!

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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.thumb.jpg.ce72023648a190e4e5a9efc6d48ffd86.jpg

 

pram2.thumb.jpg.324c4a62c8f48979e48b4c2dabaed350.jpg

 

Pram3.PNG.4aac6a60a959c8d7664c538ba69fd1ad.PNG

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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).

 

Pram3.PNG.4aac6a60a959c8d7664c538ba69fd1ad.PNG

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

 

ISkHLgdtksVDze4bvBYikGJZrSMMWwkNnOv7x8yI6raD16KsS5Z5OL2dnArilu0zLr9uC08LM9xhFi3oZKsjFcM9PZfazTS8KvkK4VnLFAyE5E4g-NqRwudWaM_iUeV9PCBJr9wg9kHFywmln1qJTmaFzi80yzgXgnZIliu3LXFTFlKQTJB9tINNqizW0Ru93l1yd_Kf1KHlhwckivU31X7p-wZRn6EEnrk_wUkRMLvJapmSS90fh39DKorq55SK3i-oKvhgIRJmXhw_F-EGIJGKY5Bh4tJDcnAFRY1tQCPThnUvNSUWuZ08RMxQ9baFF2vt_vbmD39n71BB4IlEeCD3JF7E6Ad5REFVAbigJlaKhshTba9O0_L5-XhrKkNizG3DJc-_gupV7G14NlRapSf9a072J-kf15Av3LThNvWKZy4wmqgVx1o70ah9NsoPbSUpni8OM11TkiwukY14ciJX3GlMii8i9YZt34oqYBLvy4xwL3TV5M9mYulazV-hnPOZ4-EroMDL5VQD4SkZ6sQGPTqK97iuGgorochy_-nI4yTbQGW3k220PPFy6XJwWZWnXtRz5_tXYrUobYfLiumcAbHr-UeUUjNksezYJxXjv73wYYd6l_-oTPjCaA1MaCNW-DbLrSKP7V1SHGsy45rGeTBkguvNJhdKDw4k5lm6CSUClgA5psOLMAqzTQ=w1469-h1075-no?authuser=0

 

 

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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. 

IIfxbatteryholders.jpg

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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.

 

IMG_20201213_191914_crop2.thumb.png.ca1a76d509d21f733e901dcff7241bfd.png

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I’d originally posted this on another duo thread, but figured it would be better off here

Duo PRAM battery fabrication:

 

I ordered 2x of these from Amazon. They’re 3V lithium rechargeables, with solder tabs to make the job a little easier, and hopefully keep too much heat from the soldering iron from reaching the cells.

 

https://www.amazon.com/dp/B07W4NWHJ8/

 

The first image shows the battery I took out of the machine. The red wire is connected to the positive (+) terminal of the top battery, the white wire is connected to the negative (-) terminal of the top battery and the (+) terminal of the bottom battery, and the black wire is connected to the (-) terminal of the bottom battery. I desoldered the wiring harness to reuse for the new battery.

 

I bent the solder tabs on the new batteries to put the stack together. The (+) terminal of the top battery got bent all the way over, and the (-) terminal got bent flat so that it (just barely) protruded out the side. The (+) terminal on the bottom battery got bent flat to make a long tongue, and the (-) terminal on the bottom battery got bent all the way over. Then, I soldered the (-) terminal on the top battery to the (+) terminal on the bottom battery, and finally resoldered all of the wires, with the white wire connected to the middle “tongue” and the red and black wires connected to their respective terminals. Some heat shrink tubing and Kapton tape finished it off.

 

Try not to hold the iron on the tabs too long as you’re soldering to them - you want as little heat as possible to get into the cells. Mine is working, but I suspect I was a little slow and may have shortened their life expectancy - but it’s hard to tell.

EC2578E5-F9FC-4DF1-AF17-2ECFFED9238A.jpeg

A1617A1A-3FAF-4658-B8F6-82553BA46CB8.jpeg

1FD30116-5A8E-4615-8D42-F87557D4219F.jpeg

E2375DAE-D2CA-4D5A-87F1-28F1A12C897A.jpeg

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Would using 1 18650 in the 1/2 AA macs be overkill? I hear more about them leaking and exploding from being overcharged rather than drained completely. I've got a box of "dead before 2010" li-ion packs made in the early 2000s, of nearly every manufacture; with no leaks to attest to their shelf stability. They're cheap, high capacity, a holder is available, or they can be bought with leads presoldered. I have a couple, made in single battery packages that came out of cheap bluetooth speakers( whose usb ports were on their way out). I've been using one to successfully jump the IIfx's PSU, but it sucks to leave the case open. I wonder would extra the .5v and roughly 2200mAh of the 18650 eventually cook the PRam if left connected?

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I like the idea of a dummy cell.   That said I don't see a problem buying the correct battery.  Amazon sells the 3.6v battery in several brands, thankfully no maxell red bombs.  I have used EBL brand and they come in  (2) 2 packs (4 batteries) for $8. $2 a battery is much cheaper then they used to be thanks to the fact that they are used in a lot more electronics today.   They claim they don't leak or rust and claim a 10 year shelf life.  I have not had any problems with them. 

 

Of all the solutions above if the batteries were really that hard to find and expensive, I would use the clear dummy cell so I don't have to modify my logic boards.

 

  

Edited by Zippy Zapp
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I would trust the batteries in the Macs. It depends what your usage is. Apple trusted them to not randomly explode over the lives of the machines themselves. I have no scientific basis, but I never saw any explode over at least the first 10 year life of any of the compacts I have. I would probably just swap them out as you get close to that mark.

 

I would NOT just store them with a battery; who knows what will happen in the back of your closet. I think the good rule of thumb is like winterizing your car: you stabilize the fuel, block the exhaust, inflate the tires, etc, then get it ready when you want to drive again. Same here: pull the battery for storage, and pop one in when you expect use for a while.

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20 hours ago, Zippy Zapp said:

 

Of all the solutions above if the batteries were really that hard to find and expensive, I would use the clear dummy cell so I don't have to modify my logic boards.

 

  

 

I'm kind of weird like that too. I don't want to modify them any more than I have to. Of course, I have no problem soldering in a 1/2AA holder in place of the directly soldered batteries. You CAN find those with leads, but I'm not going to go that far for originality.

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On 3/7/2021 at 3:32 PM, LaPorta said:

 

I'm kind of weird like that too. I don't want to modify them any more than I have to. Of course, I have no problem soldering in a 1/2AA holder in place of the directly soldered batteries. You CAN find those with leads, but I'm not going to go that far for originality.

 

Yep I would do the same.  Fortunately I have not owned a Mac model that had the battery with leads soldered on.  One of the revisions of the Apple IIGS came like that and I would replace it with a holder too.  None of my macs came that way.  I did get one Mac used, a PowerMac G3 Tower beige that had a leaking battery that destroyed the battery holder and corroded the frame.  It didn't do any damage to the logic board though, thankfully.  I forget the brand but it was not a red bomb.  On that Mac I soldered in headers so I could unplug the battery holder and put leads on it so it could be relocated away from the area.  But if I did it again I would probably just reinstall the battery holder and do like you said pull it if it gets stored.  It matters not on that G3 because it is in my going to sell queue. 

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Posted (edited)

I had a question about voltage...

Early compacts use those tall 4.5V cells, then desktops and some compacts started to use (one or two of) the 3.6V half-AA cells. And then some models went to the cuboid 4.5V blocks...

 

It's well documented that the floor of proper operation is 3V. But is there, for example in an SE/30, a problem resulting in damage from using a 4.5V cell? Apologies if this was answered elsewhere, but is that if 4.5V is too much for some models?  Based on some conversations, it seems that >5V would definitely be a problem, but are there board eccentricities that would preclude the use of 4.5V? e.g. using a 3x LR44 battery holder.

Edited by jessenator
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