String33

I’ve had the Ctek MXS for a few months now. I hook it up via the cigarette lighter in the footwell. All good. But the other day I was in the garage and it was crazy quiet - you could hear a heart beat - and I heard a very low volume hum or buzz coming from the Ctek. It only seems to hum on stage 7. No hum on the other stages. I have to put my ear right on it to hear it. Anyone else?

Chrismalberts

I'd imagine that this is pretty normal and that the contents of a trickle charger include a step down transformer and a converter (just guessing based on HS physics). Transformers tend to buzz.

String33

Thanks! I called Ctek and they said it was normal too. So I feel better.