A hearing instrument system with a rechargeable battery or accumulator is optimized for everyday use, in particular for EOL detection, and the performance and service life of the accumulator. A hearing instrument, an accumulator system, and a charging system each have an energy transfer interface and a communication interface. The energy transfer interface and communication interface on the accumulator side can establish an energy transfer link and/or communication link on the charge and hearing instrument side. The accumulator system provides energy to the hearing instrument and transmits state of charge information generated by an accumulator control facility to the hearing instrument by way of the respective communication link. The transmission of the state of charge information enables a reliable state of charge detection in the case of batteries, whose state of charge cannot be identified on their voltage, for instance Li-ion systems with closed-loop controlled voltage.