Well, yeah but you should try a new sim card anyway. I worked some years with photography, and I noticed that some flashes used to have less battery life than other because of heat, considering it helped oxidating it. At 0 degrees for example, you shouldn`t have considerable loss of capacity in some months, but, let`s say, in maybe 4 months with an extreme condition of 50 degrees ( !! ) you would be losing around 40 %.
Sorry for bad english =p