Pulse Width Modulation (PWM) charging may cause a buzzing noise in the system during charging. PWM switching noise can sometimes be heard in the controller itself, the wiring or wiring connections, or the system loads. AM radios are especially prone to PWM interference. Noise in the controller or wiring is caused by mechanical resonance when current is switched through the circuits. There is little that can be done to remedy this issue.

However, PWM noise in the system loads can usually be reduced or eliminated by the following:

1) Minimize cable runs between components
2) Twist power pairs(+/-) to reduce radiated noise
3) Good system grounding
4) Add capacitance across load power(at load input, 22000uf or more)
5) Add a line filter. some have had success with car audio filters that eliminate alternator whine