ARC voltage reducers allow you to control a 25 Amp load and has a remote reset circuit breaker built in. Unlike the old power resistor approach to dropping voltage, this unit does not run hot and will only rise 38 degrees Fahrenheit at full load. Also its output voltage will not change as the current draw through it varies as in the power resistor approach.
Model PWM1612A will allow you to control the output voltage anywhere between the input voltage (max 20VDC) to zero
Dimensions: 6.5"L x 1.6"W x 1.2"H. Weight is 7 ounces