batterycharging
I got a second-hand MBP about a week ago and today I noticed that when I ran the battery to around 50% it wouldn't charge back. I installed coconutBattery and it shows the charging rate fluctuating at 0-10W.
How do I make my MBP charge properly? Could this be due to faulty charger? I already tried a SMC reset.
Finally, I gave it to the Apple authorised repair centre. They told me IO chip and wire had to be replaced. Since it was in warranty it got it repaired for free.
I finally fixed it today. It turns out the Magsafe DC-in board can be replaced. It's a little $25 part ($15 refurbished). I followed the instructions on iFixit.com; you have to take apart practically the whole laptop which includes a lot of tiny, tiny connectors, but it's doable with just a few screwdrivers and a spudger I made from a chopstick.
The battery now charges fine, and the laptop doesn't get nearly as hot (that could also be because I cleaned the heat sink).
Best Answer
Just to clear this up, this was a 13'' MBP.
I've tested with other chargers and other people's MacBooks and found out my charger was faulty. Got a new one and everything is fine.