Abstract: A rechargeable battery pack, or accumulator pack, for instance for a hearing instrument, has a minimal installation size and high energy density. The accumulator pack has at least one rechargeable battery cell, charging electronics, signal electronics, and signal contacts. An encapsulation protects against moisture and contamination. The signal electronics transforms an output voltage of the battery cell into a predetermined voltage, which is made available by two signal contacts outside of the encapsulation. The transformation of the voltage enables the battery systems to be used with various battery and/or cell voltages. Li-ion battery systems, which generally operate with 3.7 volts, can thus also be used in hearing instruments, which generally operate with an operating voltage of 1.2 volts. The encapsulation of the accumulator pack is particularly advantageous in this context of the higher voltages.