Transcutaneous battery recharging by volume conduction and its circuit modeling.

Many implantable devices require large capacity batteries implanted in the body. Transcutaneous battery recharging can effectively maintain the longevity of these implants. Based on this consideration we have developed a transcutaneous battery recharging circuit unit which takes advantages of skin volume conduction. This unit is able to pass 2.8 mA from the outside to the inside of pig skin with a current transmitting efficiency of 27%. Theoretical analysis and experiments have validated that this battery recharging technology is an effective approach. In this research we have constructed an x-type equivalent circuit model of skin volume conduction for battery recharging. The parameters of the x-type equivalent circuit can be easily measured and used to evaluate the battery charging system characteristics, such as the rechargeable prerequisite and the current transmitting efficiency limitation. We have analyzed the transcutaneous current transmitting efficiency by applying the x-type equivalent circuit model and discussed approaches for enhancing current transmitting efficiency.