Reset your SMC. Instructions for doing that are [http://support.apple.com/en-us/HT201295|here]. What kind of shape is your battery in? What color is the magsafe LED, is it bright or dim? It appears that the NVRAM gets it's power from the main battery on these. What are the last 4 characters of your serial number, to help us confirm the exact model. Resetting the SMC should do it unless there is a problem with the battery or board. Has this been dropped or exposed to liquid?