I just bought a used Macbook late 2008 unibody version. Everything seems good except some quirks with the battery. It was sold to me while running OS X 10.9 (13A538g) which I understand is a beta. Could that be the cause of these problems/should I try to revert to an older OS? It charges slowly (like 3-4 hours) despite only having about 2-2.5 hours battery life. I thought if it's quick to drain, it's also quick to charge? And while charging, the estimated time left to recharge goes up and up for a while, then eventually descends but very slowly, like takes an hour to go from 0:55 to 0:30 - even though I'm not doing anything very intensive on the computer. Another thing is the battery indicator near the clock will say fully charged, but if I unplug and replug the charger it will show some amount in the 90s. Then very soon it will again say fully charged, and the whole process can be repeated if desired. It also drains a lot overnight while sleeping, like 30%. So far I have done an SMC reset (or I think I did - I don't know if it was successful). I have also made sure there are no runaway CPU processes. Now I'm planning to charge for 2 hours, run down the battery, then let it rest for 5 like Apple says to calibrate the battery. But if that doesn't work does anyone have any suggestions on how to fix this, short of buying a new battery? Coconut battery says 83% health after 1238 cycles and option-clicking the battery icon says condition is normal.