Recently my 2012 15" Macbook Pro has been cutting out without warning, even when there's plenty charge left on the battery. When I go to boot the machine back on again I get the 'no charge' symbol and it will not boot up until I plug in the charger again. Then it will turn on and work as normal. Why is this happening and is there a resolution? When I check battery condition it tells me to 'service battery' so perhaps this is related? Any help would be greatly appreciated! Thanks.