TXApex

So here at the office my boss has a 1100 CA battery out of a Semi truck that he keeps charged up to start his Lola...

I took it and put it on the S with a pair of pretty thick jumpers and got the same, slow cranking like it was a bad/dying battery. We noticed that the cables got quite warm, telling us that it was pulling a good number of amps.

Thinking that it might just be a short in the car's battery we disconnected the terminals and had only the Semi truck battery hooked up to the exact same effect; Slow cranking and warm jumper cables.

I'm now thinking that it's not the battery that is bad, but something else shorting out somewhere in the system, but what and where? If it was a failed starter I would think that I wouldn't get any cranking at all, so along with the other electrical gremlin that I'm chasing I wonder if this might also be indicative of a bad ground? Probably going to have to get it towed home

TXApex

For grins I went back out and with the car battery negative disconnected, went from positive to engine block for a jumpstart with no difference in effect. Slow movement on the starter.

I've had starters fail before, but when they went there was no 'slow turning' and I'm really not looking forward to getting at that top bolt

TXApex

Solved. The moral of the story is that if you have a catastrophically failed battery, a jump start is probably not going to provide enough power to properly spin the starter on a S2000.

The tow truck driver had a portable jumpstart box with very large, rather short cables that was enough to start the car on it's own! Going to pick up a new battery tonight. I've currently got a Bosch that has a 2011 sticker on it so it's about 3 years old now.

StormTroopinAP2

Duralast Gold from Autozone

s2k manic

you got it right a bad battery will suck all the current from the good source. for the money duralast is about the best or interstate/optima if you don't mind spending the money which after all isn't too big a difference as the duralast is 150$

TXApex

I had gone so far as to pull the negative terminal from the battery to completely take it out of the circuit. Still just gave me slow turning. I think the jumper cables that I was using might have been part of the culprit. The fact that they were getting hot tells me that it might have not been that the starter was pulling all that much power, but that the cables themselves were possibly adding quite a bit of resistance.