A:Answer Battery life varies considerably depending on the model of device you have. The best way to compare a new battery is to compare it to your old battery by the mAh or Wh, which indicate how powerful the capacity of a battery is. Even though this doesn’t give you a run time at least you know if you are getting a battery that is comparable. These batteries usually give their best performance within the first year, though as they are used more and get older their runtime does diminish. If you have any further questions, please let us know!