RE: What the heck is going on with my Tsunami?
I'm not familiar with the Redcat system, but Lipo is not necessary to run brushless. My buddy runs all NIMH in his rustler VXL and it cooks along just fine. He runs everything from cheapos to Venoms to Maxamps to GP's and they all work fine. Maybe the Redcat system demands more amps? I don't know?
Are the batteries in decent shape? A decent brand? What kind of connectors are you using, because if they are Tamiyas then you need to dump them for Deans.