I was sitting in traffic in my Rx8, and I have a 6 speed manual. For some reason when I went into 1st gear, the car died and just the battery symbol came on. No CEL. I'm gonna assume it's the battery, but when I started it right back up it had no issues whatsoever. Could this be something with the ECU?

I wanted to be sure because I didn't want to do anything that was unnecessary. Thanks again!

 

well it could be any number of things, but I might check the battery connectors first. Like most japanese cars the OE connectors are junk after being taken loose a time or two. Then they become loose and not making good contact. Just too thin and stretch too easily. Had the exact same problem on my two street Hondas.

 

will double-check that, thank you!

 

Do you know how old the battery is? I just replaced a super old battery in my other car, it was kind of holding a charge and would start, but a lot of weird random things would happen because the battery was all over the place.

 

the battery is actually just a year old! i figured it out due to the connections, but everything runs like a charm! and she still pulls harder then my loan at 8k RPM

 

I would guess the battery symbol came on because the alternator stopped with the engine. The CEL doesn't come unless it has a specific failure to report.
Would be surprised if the battery or connectors were in poor enough state to stall the car, but still in good enough state to start it immediately after. Starting is far more demanding.
Are you sure you didn't stall it?