I rebuilt my starter just a while back and now I started to have this problem where I'll get one good start and then when I go the restart, I get nothing. At first I thought it was my key switch going bad because I could just jump it with a screwdriver. But not it's worse. It would get harder and harder to start that way and I just made an override button under the hood and I got nothing. I check it out and was getting 2.5 volts. So I yanked the battery and it read 3 volts. In a few minutes I read above 7 volts. I put it on the charger now. I wasn't expecting it to be like that. I replaced the alt about 2 and 3 years ago. I guessing that there is a bad diode somewhere so the alt is not charging. What's weird is when I could get the starter to crank, it cranked at a normal speed. It never seemed slow. So now I've got a bit of troubleshooting ahead, but my guess is that it's in the charging system.

 

After you charge the battery have it checked to make sure you don't have a bad cell. Then after you install it just do a simple voltage test. With the car running above 1000rpm you should be getting between 13-14V. If not then you have an alternator problem. If OK then you have a drain somewhere in the system. Then the fun begins. Good luck.

 

As well as charging and checking alt output, clean terminals and terminal connections and ground connections too.
This is a good tutorial in sorting charging problems:
Voltage Drop Testing
Ed