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Warning! Exploding Maxell PRAM Batteries

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It still bugs the crap outta me as to why they use that big honkin 2200uf cap, where a normal 47uf 16v cap normally is.

i just kinda wanna know why is all. :)



With my LC, I clipped that big cap off and just installed a normal SMT 47uf 16v cap and it works fine.


wash up that board buddy real good maybe it might still work?

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Oooooookay after reading this thread I am most definitely goin to make a concerted effort to unbury all of my stack and pull out PRAM batteries like a madman... I know a few had Tadiran cells but there were a lot with Maxell ones.Might be time for a trip out to the farm this afternoon for sure. 8-o

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OK so after I'd read this threead over the weekend I quickly set about digging into my collection to inspect machines or pulled boards for damage and remove all batteries. I have gotten through 18 units so far... 2 SE's, 2 CC's, 3 IIgs's, a IIci, a IIsi, 4 LC's, 2 early and 1 late LCIII, a Performa 400 (LCII), and an LC475... plus a few pulled boards (Classic, 475, PM5200, PM7xxx) This is the results of the sweep so far... news is good but not great. :-/


Firstly I checked out dad's SE and found an intact Tadiran battery with 88 date code which I promptly removed. Then it was time to go through mine...


Before I had even started sifting through the stack, I found 3 Classic logic boards... the first had clearly had a battery explode already, which I could no longer find any viable trace of to discern a brand... only the aftermath below. I'd call this a parts board now at best...




The second one had not been demolished so impressively but nonetheless had a badly degraded Maxell that had leaked and started to corrode the caps, a couple of diodes, an I/C and a rectifier in the immediate vicinity. The finger contacts are also damaged as well as some corrosion on the bottom of the board, but i believe this may be due to it's proximity to the exploded battery, which was on the board beneath it in a stack.






The third one that was on top, as well as the RAM stacker and SIMMS connected to it, and the other stacker sitting on top of it, were luckily unharmed. Incidentally, this third board had a different battery of German origin, blue in colour, that appeared fine. I have found a few of these in the machines I've investigated so far...




Next victim was this LC475 board I pulled from a machine years ago. This one however was not recently exploded... This corrosion was present when I got the machine nearly 10 years ago hence it's non-functional state. Thus far most of the LC475's Ive had from memory have had Maxell batteries.




After that, was time to get into the complete computers... First in line were my trio of IIgs's. The first two were fine, with no signs of leakage. I believe one had a Tadiran and one a blue . Then I opened the Limited Edition (which has the PRAM battery soldered to the board on legs underneat the PSU), and found a Tadiran that was obviously original and in a very sad state. the casing was deformed, it had clearly been leaking and there was corrosion beginning on one of the feet. After I snipped it off, I found the lower surface of the battery casing to be very poorly. I'll be pulling this board out over the coming days and washing it just to be safe and make sure no trace of goop remains...




The CC's both checked out fine, as did the IIci, IIsi, LC's, LCIII, and Performa 400... No real signs of serious degradation in the assortment of blues and Tadirans aside from very minor specks of corrosion beginning on the endcaps of a few of the 80's and early 90's coded ones. There was one Maxell in the lot that seemed ok at a glance aside from similar endcap corrosion...


Then I got the the last of the pizzaboxes, my only remaining operational LC475, and was saddened to find my first real irrecoverable Maxell victim...








I guess I don't have a functioning LC475 any longer. :( It looks like there must have been a decent amount of heat going on in there when it happened, and it looks to have been a pretty violent reaction too... the stuff reached all the way to the very rear of the case, and seems to have eaten away at the actual locking tab even as it snapped like a cracker-biscuit when i began to open the case as you can see, as well as rusting one localised corner of the PSU case and destroying everything in it's path on the logic board... and even the fan copped a little!


I've now written this one off as junk and stripped it... luckily there was nothing in the PDS and the RAM and VRAM modules on the board seem to have miraculously escaped unharmed. The HDD was luckily shielded pretty well by it's own SCSI cable and the FDD was far enough out of the way to escape without injury. I'm going to pull the PSU apart before I use it to make sure no stuff has not gotten in and began eating away the internals. Ah well... guess I'm on the prowl for a new LC475. I don't even have a spare case anymore, as I threw most of em from the ones I stripped out to make room for working stuff and kept only the best one, which is now junk. Ah well... :(


ANyway, after that devestaing blow I investigated one of the prides of my collection expecting the worst But interestingly, upon opening my nearly mint SE Superdrive, I was not only pleasantly surprised to find an unharmed logic board and analogue board with caps that look as good as brand new, and not a single silver and black cap in sight, but also this Varta battery... also soldered on feet like the IIgs LE, and a date code on it that would indicate it is the original 25 year old item. It looks like new too, and from memory this machine actually still kept reasonable time after 25 years. My dad's SE FDHD even had only lost a few hours in the last 7 years with the original Tadiran.


Anyway... after the devestation I found in my 475 I'll be continuing my investigations post-hast, as I suspect at the very least my working Classics all have Maxell batteries onboard still, as well as the SE/30 and there is a good chance I may find some in the LC 5xx and early Powermacs, and the IIvx and other IIsi that I havent checked yet.


As an aside, these machines were all sold in AUstralia, and as such, many came from the Singapore factory... Incidentally, most of the machines of Singapore origin do NOT have the Maxell battery onboard, and the ones that do have it have all seemingly been manufactured in the USA?

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Yep... any of the oldworld stuff I'm just pulling em all out. Any that look remotely dodgy, are stupedously old, or are a Maxell in any condition have been already thrown in a pile to be disposed of. The ones that are left have been put in a seperate pile away from anything important for in the event i need one. They will probably be tossed as well however, as for what its worth, I have plenty of new-world stuff to pull much newer batteries out of, or I can buy them new cheaply enough off ebay anyway.

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WHilst I think about it... has anybody ever had issues with the cube PRAM batteries used on the PM5500 and some other later Powermac logic boards that are velcroed in place? Wondering if I should pull them too... they are somewhat harder to get replacements for.

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I havent seen one leak, but i DONT take chances. I pulled them, cut the pigtales and tossed them. Kept the pigtails in case I want to patch a new battery in place, via a battery holder.


Even the powerbooks, have the little rechargeable coin cells, I pull them too. they are starting to leak. and they are positioned in such a way it will leak all over the logicboard.

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How about the auto-inject FDDs?


Many of them are approaching a senior status and yet to this point I haven't heard much in terms of failure on their part other than mechanical works.


There are a couple of tiny electrolytic caps on the standard 1.44MB auto-inject. I didn't have the brand-new 800K disk drives that I picked up long before they were snatched up by CC_333 so I didn't get a good look at them.

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Typically the Sony mechanisms are pretty reliable. I've had a couple that wouldn't read disks, but, one was due to a dodgy motherboard that didn't work with an 800K drive either. The other I suspect was just so dirty that it couldn't read a floppy without errors. Caps looked decent on the boards.



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Mmmm onlky issues Ive had with SOny drives have generally been due to mistreatment and are usually mechanical in nature... things bent, broken or chucked out of allignment due to being dropped or having disks forcibly wrenched out of them etc. Electronically they don't appear to have any endemic issues as yet. :)


And yeh I cut the pigtails as close to the battery as possible on the SE and IIgs... left plenty to play with for in case I ever decide i want a plastic holder in their. :)

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I just wanted to confirm that I've also seen this happen with pretty much any brand of battery so it's not a really Maxell problem. I've noticed it's most likely to happen, but obviously not limited to, the really compact models like the original LC line. Obviously in more confined spaces there's also more damage. I purchased a pretty large lot of Mac and IIgs systems around 2006-ish and at least half the Macs and a handful of IIgs's were a total loss because of the batteries. :( I'm sure storage conditions also contribute the the explosive failure rate as a lot of those system appeared to have been stored outside at some point, most likely as trash...


I'd also like to note that I've never seen it happen to the solder-on variety, only the replaceable ones.


These days if I don't plan on using a system for awhile, I always remove the batteries. Better safe than sorry, even with new batteries in them. (Battery quality seems to have gone down so...)

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Have to agree with the above... however it'd seem the explosive failures are generally limited to the Maxell ones as a rule of thumb. Even so, not worth taking the chance on any... Had I known or more to the point simply thought of this years ago, I'd have saved myself a few dead Macs by now.


Also, with regards to my earlier question regarding the square batteries, I sifted through my entire collection of 5xx LC's/Performas yesterday and it would appear these square clock batteries used in the LC575, Performa 580, and many variants of beige Powermac are also beginning to fail... I've thus far lost one 580 board to a badly leaking cube battery, and found others in LC575's that have begun to leak, so it'd be a good idea to remove any of these also.


Incidentally in this latest raid, I came across another Maxell that had ruptured less violently but had nonetheless leaked out and destroyed the logic board in a 520. :(

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If the capacitors don't get them, the batteries will!


These Macs are beginning to become very high maintenance in their old age.


I'll have to check some of my machines (though, to my knowledge, none have the Maxell batteries, and those that did had them removed; this doesn't make them immune, however).



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Who isnt high maintenance in thier old age? Think about that sentence for a few minutes. lol. Cars are a good example. Grannys are another one.


This might be stretching it a bit, but in some cases its worth baking the boards at a moderate temp (high enough to drive moisture, low enough not to melt plastics or blow caps). Or simply remove non-reflowable plastics, and the caps (you have to anyway).


Wash and bake.


This will drive out the moisture out of the PCBs, and especially the ICs. Then you can store the boards in desiccant filled antistatic bags.


This will reduce chip failure effects from aging.


I know this is a factor, because I had ordered some chips from digikey for replacement parts, or new builds and some of them come in a dessicant sealed bags with a shelf-life. Why? because they absorb moisture and can cause cracking/bubbling when doing a reflow. And of course, moisture can oxidize the metallized layers on the silicon die, causing leakage, noise, and shorts. (why old transistors are very noisy and temp sensitive especially in vintage audio gear). Now this effect is really really really minute, but that possibility is always there.


You wont totally prevent it, but you can definitely prolong it. That is the one thing that has me concerned with CMOS and TTL ICs, or any IC for that matter during the aging process. How much does the moisture exposure, get absorbed into the IC package, and then how long does it take to oxidize and eventually effect the core.


I think its already happening (bad ram, random bad SCSI ICs from sitting, or other random IC failures), but I just cant prove it. lol. How else do you explain putting a peice of arcade, or computer hardware that worked perfectly away, set for 20 years, come back and recap but it has bad RAM now. or some other weird failure.


Sorry for the ramblefication, but i had to throw my 2 cents into the pot.

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It seems the removable batteries started showing up late in the SE run, and probably in the middle of the IIx run. Had a IIx board that had two PRAM battery holders instead of the soldered batteries.


A solution on those machines that have enough room, might be to use a triple AA battery holder, and three rechargeable AA batteries. Would be exactly 3.6 volts when charged up.



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