Lately I was experiencing a few random things with my MacBook Pro like battery was draining really quickly - even just idling, random crashes etc. The activity Monitor was was telling me my battery life was 2hours on 100% battery. I did a little digging and looked up the spec for my MacBook and how many cycle counts until my battery was deemed ready for replacement. It was 400, so clearly battery was still good. I looked up a little trick that worked for me, Resetting my MacBook's PRAM. After resetting my PRAM my laptop stabilised and battery life went back to normal.

Here's how to reset your PRAM.
1) Shut down your laptop.
2) Plug in your MagSafe charger.
3) Turn on laptop, immediately pressing Option Key(alt) + Command + P + R for 20seconds.
4) Wait for laptop to Boot
5) Adjust any of the preferences on your mac by going back into preferences.

This worked a charm for me, as my battery was still in a good condition. It's worth checking your cycle counts to see if your battery is still in good condition. More information can be found on the following support links on apples website.

https://support.apple.com/en-gb/HT201585 (MacBook Specs)
https://support.apple.com/en-gb/HT204063 (Resetting PRAM)