I've been helping my friend with their MacBook and seems the battery is shot. The laptop only works when plugged into the wall, but when a different battery is swapped in it works fine. The battery just isn't supplying any power. It's not on AppleCare so seeking out a replacement from Apple isn't an option. A new battery from Apple is $129 I think. I noticed there are several options online such as used OEM batteries on eBay, generic batteries, etc. What's the best option while still staying on a budget? Some of the generic batteries are in the $49 range, which would be nice. Also, what about high-capacity MacBook batteries? Do these hold up to the promise?