i have done about 4 of them different ways, the last one i did, placed the battery on a 2x4 and used a dead blow and hit the seam all the way around and it broke free , turned out pretty ok,  got the idea from someone on this forum infact. i think it was james in texas.

I gave the battery to an "expert".

He cracked it open and replaced the cells inside.

Total cost was high but not unreasonably high, about 60 euros for the batteries plus fit.

Knowing that one battery costs nearly 20 euros at my local equivalent of Radioshack, it was definitely the best thing to do.

I tried with a flat-head screwdriver but I knew I was going to ruin it. I think he did a pretty good job. I'm going to get it back this week.

Uniserver's method should work pretty well

The only thing i'll add is that if you can't get it to crack take a sharp knife and score round the seal and try giving it another go (this is what I did with my duo's battery, which i still need to recell...)

Great, thanks for the tips guys, I'll give it another go with your techniques!

@BadGoldEagle, gotta keep it cheap for now, so it'll have to be DIY!

Some years ago I rebuilt several batteries for the Mac Portable, and I found that by using a hack saw at the seam it was fairly easy to cut off the top and remove and replace the guts! First find a battery of same specs that will fit inside the case and then solder the connections, and replace the cover with a very neat glue appliction!

when i re cell them i always just use this... it works out really great.

http://www.ebay.com/itm/UPG-6V-5AH-UB645-Replacement-for-UPS-Battery-for-APC-AP200-/191402741759?pt=LH_DefaultDomain_0&hash=item2c907e0fff

As james_w in the uk i'll add that I used this battery for mine : http://www.componentshop.co.uk/6v-4-5ah-sealed-lead-acid-battery.html(they also carry a 5ah battery of the same size and price: http://www.componentshop.co.uk/6v-5-0ah-sealed-lead-acid-battery.html (i'm sure that one cost more when i brought mine) )

Currently i have just soldered a couple of croc clips onto the battery and i just clip those to the contacts in the portable (I haven't got around to recelling the orig pack yet)

A drill press (or mill) and a 1/32 end mill below the parting line. Replace the battery, then I use beige caulk so if I ever need to get into it again then it's just a razor blade. 

Don't give up with old batteries. The Portable uses a lead acid battery, which can be exercised, possibly to rejuvenation. Boaters know people who have battery exercisers which can fix a battery. If sulphination kicks in, it is not necessarily a death sentence.

I like the mallet idea, but to date have done a few of these things by scoring along the seam lines with a knife or razor saw, then taping the thing back together to facilitate easier rebuilds next time. But if I were actually going to use the thing regularly? Forget the expense of rebuilding a stock battery: Open Portable housing, remove stock gold-plated battery terminals from battery bay (they are clipped into place and wired in via Fastons). Build new battery leads with spade connectors on one end, and Fastons on the other. Snake them through suitable opening in the battery compartment. Now just use any suitably-sized 6V battery with Faston-type connectors. Best of all, these mods are fully reversible. Had previously connected a D nicad pack that way and it worked great. NIMH should work too, but I probably wouldn't leave them sitting on the charger longer than I had to.

2V 5 AH Enersys Cyclon batteries are still available but kind of expensive and neither Mouser nor Digikey sells that particular size.

I've used the 12V version of this to revive a dead AGM car battery:

http://www.batterytender.com/Chargers/Battery-Tender-Junior-12V-0-75A.html

But did have to clean up a puddle of acid afterwards: I guess the process must've been causing the battery to bubble with hydrogen gas. Fine for a wet cell with vents but I dunno about doing that with a sealed battery.

Charlieman said:

Don't give up with old batteries. The Portable uses a lead acid battery, which can be exercised, possibly to rejuvenation. Boaters know people who have battery exercisers which can fix a battery. If sulphination kicks in, it is not necessarily a death sentence.

Click to expand...

It's dead, Jim. It's a 25+ year old lead acid battery. We have a hard enough time finding good batteries from the 90's and early 00's. Replacements are less of a hassle and risk of dramatic failures.

Personally I'd use any combination of 2v cells or one 6v cell that would fit in the old enclosure.

Great suggestions everyone.

I'd like to dispose of the current cells so will open up, but I also have a replacement battery that is rated exactly the same as the original so may well go down the route of making some leads to run from its terminals to the Portable's.

I just did this, I actually just popped it open with a screwdriver and radioshack sells a 6v 4.5AH battery that fits snugly into the old battery for 20 dollars...