resistors - Buck Converter for 59V to 58V?

Some batteries last twice as long if they are kept to 80 percent of their maximum charge. It's good to add a small adjustment to undervolt a charger output by 0.5 - 1V. Myself i have a CC/CV charger that is .5 volts too high for a given BMS.

How can I take the voltage down by .5 - 1V at the output?

Answer

^{simulate this circuit – Schematic created using CircuitLab}

Figure 1. \$ V_{OUT} = V_{IN} - 0.7 \$.

A silicon diode will drop about 0.7 V when more than a few milliamps is running through it.