PCA SDR

I installed an Odyssey battery in my track car. I also installed a kil switch (the good one). I didn't hook the switch to the ECU, so it serves as a battery cut-off for now. I t worked flawlessly at Coronado. it has been sitting dormant pretty much since; I have only started it and warmed it once since, I think. Issue:

After charging the battery for a couple of days, It didn't seem to have enugh juice to start the engine. It would turn over for a second or two and then, nothing. Classic dead battery symptoms. i took the Optima oput of my truck and hooked it up via jumper-cables, same effect. I went and bought new jumpers (mine were old, cheap and rusted) and got cables long enough to reach the battery from parked directly behind. Standard hook up to a disabled care, with the truck running. Same performance.

Whar should I try next? Disassemble and clean all connections relative to the batter and switch? Anything else I should check? If that turns out to solve the problem, is there anything (preventative maintenance) that I can do to keep this problem from coming back, or at least reduce the amount of times that it does?

Advise...

So you are saying that even when being jumped your 993 doesn't turn over as it should?
If a good battery still cranks it slowly it could be a bad connection in the starting circuit, maybe the ground strap connection to the chassis needs to be cleaned up.
Could also be the starter....

Have you bypassed the kill switch? They are often the problem and narrowing down the issue is key. Remove the switch or solidly bypass it and see if the symptoms change.