A battery monitoring means for an implantable living tissue stimulator system in which various battery voltages are telemetered to an external receiving means, these voltages being related to the internal impedance of the implanted battery. More specifically, a battery loading circuit is provided which incorporates a switch means for loading the battery in accordance with a predetermined sequence. In a specific embodiment, first and second resistors are sequentially connected across the battery. The battery output voltage is telemetered to an external receiving means during this sequential connection. By knowing the values of the two resistors, the internal impedance of the battery can be calculated, this impedance being related to the remaining life of the implanted battery.