Thanks for the advice on the voltage!

I pulled the battery to take it to Pep Boys this morning. I found quite a lot of corrosion from the vent on the negative side.


Hoping to get a second opinion on the voltage, Pep Boys said the battery is low and needs to charge. They would know if the battery was good or not after a 45 minute charge.
The guy came back with a slip of paper that showed the beginning charge at 12.26v and the ending voltage at 12.68v and says the battery is good.

Being that this is a daily driver that is the likely culprit to my mystery no start, it looks like the original battery and the corrosion its dribbled all over my engine bay - I decided to just get a new battery anyway.

The recommended battery for the crossfire was a 770amp for $149. I asked him to look up '03 SLK320 which had a second option for $104 and 620amps. I went with the higher amperage.

I haven't installed the battery yet. I scrubbed out some of the corroded battery tray and surrounding cables and sprayed some black rustoleum to cover the rust. Waiting for it to dry.

Only question is; is the crossfire supposed to have battery vent tubes? I didnt keep the little clear plastic box that was on the old battery - It was covered in orange corrosion.