Systems and methods for use in pulse generation

A method of recharging an implantable medical device after implantation within a patient, comprising:

• (a) transmitting a RF power signal from a charging device external to the patient;
• (b) receiving the RF power signal in an antenna of the implantable medical device;
• (c) rectifying a signal from the antenna;
• (d) recharging a rechargeable battery of the implantable medical device using the rectified signal, wherein the recharging occurs in respective stages with a lower charging current applied in each successive charging stage, wherein the recharging switches between stages by measuring a charging voltage across the rechargeable battery and comparing the measured voltage against one or more voltage thresholds;
• (e) measuring a voltage drop of the rechargeable battery when switching between a first charging voltage during a first stage of the respective stages and a second charging voltage during a second stage of the respective stages;
• and
• (f) calculating a new threshold value for transitioning between the first stage and the second stage in response to the measuring and storing the calculated threshold value;
• and
• (g) repeating (a)-(e) in a subsequent charging cycle including using the stored calculated threshold value during repetition of (d).