Macbook won't turn on - steady green charger light

A few days ago I shut my macbook down as normal - the next day I tried to turn it on and it wouldn't - no response when I tried to do an SMC reset or whatever they're called either. The charger light was steady green. A few days later I thought I'd try a final time before sending it in for repair and the charger finally worked (initially green for a second then steady amber) and it began to charge again. Turned on pretty much as normal except the date was 2001.

I've had some previous issues with the laptop re: water damage and a dull green light when charging/the battery not taking any charge but got that repaired a few months ago and has been fine since. It's a 2011/2 model. The battery doesn't last particularly long - normally around 2 1/2 - 3 hours if I'm doing some light word processing/spreadhseets/photoshopping. Will I need to get the battery replaced or is this a sign that something more irreparable is going on?