Cheap(er) sources of mower batteries?

Jon, thanks for the info. I don't have the old battery in front of me right now, but I think this one would be similar. Can this be taken apart and refitted with new cells?

Ooops...if the batteries are like those ones then they are not repairable--Southendguy nailed it.

The battery packs I was thinking of for drills and the like have screws holding them together and are easily opened up for repair.

You can look for any 12V lead acid battery that has the same physical size as the ones you are toasting. A quick look on eBay showed lots of 12V 18AH batteries available but not a heck of a lot less than $40 each.

If you have a decent relationship with some scrap dealers in your area who take batteries you could check them out...I've noticed that communications companies and businesses with big IT departments sometimes throw out batteries that still have some life in them. Keep an eye out when you are dropping off scrap and nab a few of the right size when they show up. Its a crap shoot if the batteries are any good but maybe you could work something out with the yard to take them and try them. Otherwise, you'd need a battery load tester with you at the yard.

Good luck!
Jon.