Power lead not charging battery or running laptop

I have just replaced the battery but now note that it isn't charging when the power lead is plugged in and it looks like the machine is running off battery. A message has popped up to say that my lead is too small, it is 65w. I have found that there are some 90w leads out there, do I need the larger one? Why has the smaller one been ok for the last 12 months and is this why my last battery died on me?