UPDATE:
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?