weird battery problems

I just rebuilt my motor (took the starter off and what not) and the battery/starter is giving me some weird symptoms. If I let the car sit for a couple hours, it cranks over and fires up just fine. If I drive it somewhere, shut it off for a brief period, then fire it back up again (such as a grocery run), it cranks slower like the battery is going dead, but it still fires up. If I were to drive it to another store, shut it down and try to restart it again, it has a really difficult time cranking the engine over - if at all. However, if I let it sit for a couple hours, all is well with the world and it fires right back up again. What's up with that?

There's no way the battery can be recharging itself when the engine is shut off, so the pause has to be physically changing something with the battery or the starter. Since the starter usually either works or doesn't work (and doesn't make any weird sounds), I'm thinking a cell in the battery is crapping out and just happened to do so while I was rebuilding the engine. The couple hour duration thing is the other cells slowly dumping power into the bad cell only to be sucked out when I crank it over, thus overloading the other cells. Thoughts?

It sounds like you have a heat soak issue with the starter motor or a connection that is loose or dirty and becomes higher resistance with the heat of the engine. Are you absolutely certain that you got all the ground straps reinstalled securely and the cables between the battery and starter cable are clean and tight?

-Rod

Everything is snug, tight, and plugged in properly that I'm aware of. It doesn't nessecarily seem to be linked to engine temp as much as the number of times I try to start it within x amount of time without letting it sit for a while. I can drive it home from work, shut it down, then fire it back up fairly easily. However, if I shut it down and fire it up a couple more times (shuffling it around in the driveway and what not), it gets increasingly more difficult to start.

When I had just put the pistons, bearings, and all that on, I did run the starter through a pair of jumper cables for a while just to make sure that everything spun properly. The starter itself didn't get very hot to the touch, but I'm wondering if I damaged something in there somehow...?

Upon further investigation (starting it up a few times consecutively first thing in the morning), it appears that you're right about the heat thing. Hopefully, a good connection cleaning will do the trick.