replacing the battery in old genesis carts

i recently won Shining Force 1, 2 and Phantasy Star 4 off ebay and found that none of them holds any saved games after turning off the system power (this didnt surprise me, i was expecting this to happen cuz of the age of all genesis carts) so:

1 - is there a way to replace the cart batteries?

2 - do i need a special gamebit screwdriver to open the carts (i saw one on ebay for $20 US, i hope there are places cheaper then that)??

3 - do the right batteries even exsist anymore???

4 - if so where could i find a bunch of these batteries for sale (hopefully not extremely expensive either)????

5 - is there a site with instructions on how to replace the battery or is it straight forward stuff with nothing complicated about it?????
you can get new gamebits from liksang

they are around $14 iirc

ive not opened up a cart to look, but id imagine any battery with the same voltage would work fine, although youd have to find some way of mounting it in there

i cant look either , since i lost my gamebit a while ago :(
also, on genny carts the screws are very close to the surface, so it's rather easy to get them out with small pliers or even scissors. I recommend replacing them with normal ones afterwards, tho.
I can't see the page you're referring to ("your dataset has expired" it tells me), but you do need a horizontal mounted battery or battery holder.

Man, I hope this never happens to me. I still have Shining Force II with a working battery. After all these years, I can still see Shade use the Gismere blade to slice up the Prism Flowers :D. Come to think of it, all of my batteries still work. I've checked Beyond Oasis, my SegaCD's battery, Saturn, all working.
yeah its strange for me too cuz i read somewhere that these batteries are supposed to last up to 5 or so years, but i have a Pirates Gold cart, man i was smart to buy that back in the day :) and the battery still works over 7 years after i bought the game (i bought it a few months after it came out)!

strange aint it
5 years is really a *minimum* lifespan for a cart battery - I have a SMS Miracle Warriors cart that's 13 years old and the battery is still fine :)

wow those are some good batteries, i wish my watch battery could last that long :(

now all i need to do is find a cheap gamebit somewhere to crack open my genesis carts (and $15 US isnt cheap, cuz i live in Canada)