Help Hard crashes - Battery bug?

[Pie77]

I'm getting really odd behaviour with my Nexus 5 after updating to 5.1. My phone will randomly hard crash and power off. When I power it back on the battery has dropped to 0% and either shuts itself off or I shut it off. When I turn it back on after a few minutes then the battery is fine again.

Battery Graph (http://imgur.com/jPSDCAz)

I thought it was related to using the camera (which is really unstable in 5.1) but it seems to happen randomly. Is anyone else seeing this? Should I just order a new battery?

 

[funkylogik]

I think I'd be tempted to try a factory reset first if you haven't already