starting/not cranking... isn't happening

[B318M42W]

hi, i was using the car for work and then i turned it off. when i came back 5 minutes later, it would'nt turn over . so here's the symptoms: ignition key on, the dash lights are weak, and if i try to start it, i can hear something clicking reallly hard. check battery voltage, 12.5... (started her up on compression) and got 13.5V at the battery. what is wrong with it again??! (and it's been driven rough for the past week or so, related??) no codes, not wet, doesn't crank... act exactly like a dead battery, but the battery is good.
terminals were cleaned, tightened and lubed.

more interesting info: initial key turn, all dash lights are dim, but after a few seconds (after the bong stops dinging me) the dash lights get back to normal. but if attemped to start, dim again with the relays clicking. also, all electrical in the car works normaly (except for that...)
 
any ideas are welcome!

[DesktopDave]

I'd get that battery load tested.  Might be high internal resistance or an internally shorted plate.  At rest the battery might be 12v, but when it's loaded up it fails.  Starters draw a lot of power.

[B318M42W]

yup... battery's dead. was confirmed by boosting the car. glad it's not the starter!