yeah...that sounds like the battery...

i'm not sure, i have the del sol S and back wen i had the singlecam nonvtec in it, the battery was supposed be 425 cold cranking amps, if its holding a low charge, it will start just as it is now.... go to a local shop and have them test the battery and if it comes out fine and ur battery starts to drain again, make sure to check parasitic draw, meaning make sure watever uses the battery after ur car is off is not drawing to0o many amps and also make sure notin extra is being left on.....just some things to ponder