Aluminium Boat and Electric leaks???

We have purchased an aluminium Boat (cigale 14) and we have a problem.

When we purchased the boat we could measure with a voltmeter the minus on the battery and the bare hull and we would get a reading of 0,00volts.

we fitted solar panels and we then got a reading from the minus on the battery and the bare hull of 2,7 volts????

We have no w installed 2 Super wind 12v Wind generators, Installed as per manufacturers instructions.
When we switch them on and they start producing electricity, we get a reading from the minus pole to the bare aluminium hull of 10,5 volts, switch them off and it immediately goes down to 2,5 - 2,7 volts.

Is this a problem and what could be the cause?????

I know that electricity and aluminium hulls can be a problem, I have read often that, the "incorrect installation of solar and wind generators causes more electrolytic problems than anything else"

Fine, but nowhere can I find What the "Correct installation of wind generators and solar panels" on an aluminium boat is?

What have we done wrong? or is everything fine and we are worrying about nothing?
Maybe by connecting the battery minus to the hull, we are causing a leak that would ordinarily not be there???

Please!!! not too technical answers, we are not big on electrics.

 

That is a serious problem. With that voltage, the electrolisis will erode the aluminum and make holes. As a first step, immediately disconnect the solar panels and wind generator. The hull should be at 0Volts to the battery. Normally there is a ground wire connecting both. Maybe you have a floating ground. That is a battery ground that is not connected to the hull and grounded to Earth.

 

Whatever voltage you measure with a digital multimeter is not relevant, it only shows there is no earth strap between B- and the hull, so your electrical system is "floating".

To determine the amount of leakage, measure the current between B- and the hull. If that is more than a few milli-amps there is a path between the electrical wiring and the hull you have not been aware of, like a mounting screw from a solar regulator. But most probably you will find no current at all.

If the voltage reading still bothers you, install the earth strap.

 

I agree that the voltage difference is not a problem as long as they are completely electrically insulated. However, a splash of water can become a conductor, or anything else.

 

There should have been two wires coming off each of the solar panel, wind generator etc that have to be hooked up to the battery charge system.

Where did you hook up these two wires?