I've got a new 12V->220V inverter/charger and it works fine, but I've noticed that whilst its chassis/cabinet is earthed, there is a potential difference of over 100V between either battery terminal and earth.

Is this normal?

Thanks Ed, that sounds like a good thing to try. I was wondering if there was a"half of mains" volts relationship.

Not having a 470k to hand, would it possibly hurt the inverter if I used a 60W incandescent light bulb?

Of course, the thing I'm more concerned about is if it would hurt a person - who happened to be touching the chassis whilst they touched a battery lead (with the unit operating).

Connecting a bulb across like that really _ought_ not to do any harm but using a higher resistance would be a bit more conservative. An incandescent bulb has a pretty low resistance when it's first turned on; the resistance increases as it heats up. That's why they turn on so quickly. [¹] [²]

Trying to think of a purely resistive low-power mains device. Difficult. Small soldering iron?


[¹] It's also something all (ex-)HP employees ought to understand - the company got started making an oscillator which used the positive temperature coefficient of a light bulb for stabilization. A few used in the making of the film Fantasia.

[²] Also, I think, why they tend to blow when you turn them on.