This paper discusses encoderless control of a permanent magnet synchronous machine that is fed by an extra-low DC bus voltage and operates within the low-speed range. The focus is on optimising the parameters of the high-frequency (HF) voltage injections necessary for estimating the electrical position of the rotor. Although the encoderless control method adopted is pulsating carrier voltage injection, the optimisation algorithm can be applied to other methods as well. The quality of the estimated position is influenced by the amplitude of the injected voltages, which also affect the disturbance of the machine torque. Therefore, this study aims to strike a balance between the quality of the estimated position and injection-related intrusion. The paper proposes an experimental approach to determining the optimal injection level, enabling accurate estimation of the electrical position while reducing torque disturbance. It also presents the experimental validation results of the optimal injection voltage implementation.