Euro Manufacturing and Marketing Ltd

UK Manufacturers of

Battery Management Systems,

DC-DC Voltage Converters and DC-DC Battery Chargers


Due to the technology involved Galvanic Isolators are a bit difficult to test. New standards are being developed that will specify self testing isolators, but there are some technical difficulties that remain to be overcome and in the meantime they have to be tested by hand. There are a number of methods that can be employed, but the one that follows is the simplest and easiest:-


1. Disconnect lead from one of the Terminals on the Galvanic Isolator so that you are testing it only.

2. Take a Digital Multimeter and set to the Diode test function

3. Put one lead from the Multimeter on one Terminal of the Galvanic Isolator and the other lead on the other Terminal

4. As the Capacitor in the Galvanic Isolator starts to conduct current, the reading on the Multimeter should rise to approximately 0.9Volts*

5. Remove the test leads from the Galvanic Isolator and short the two terminals of the Galvanic Isolator together to discharge the Capacitor

6. Repeat the test – this time with the test leads reversed. You should get the same result*

If you get the above results then the Galvanic Isolator is working OK and can be safely reconnected.

We recommend this test should be carried out once every six months.

*Charging of the Capacitor can take a little time depending on the Multimeter being used.

Interpreting the Readings

E936 Galvanic Isolator



Do I need a Galvanic Isolator?

Yes, if you use shorepower to provide a mains supply to your boat.

The latest CE and BMEA Regulations clearly state that AC Earths from Shorepower must be bonded to your Anode. As other Boats in the same vicinity as yours have the same bonding system, the Shorepower Earth Wire is potentially connecting the underwater metal parts from each Boat together. The water between the Vessels acts as an Electrolyte forming an Electrical Cell, which is similar to a low power battery. This will cause metals with a low galvanic number to transfer to metals with a higher galvanic number, which means that Electroplating will occur. This will damage and weaken the metal structure of your Boat.

What does a Galvanic Isolator do?

The Galvanic Isolator is fitted in the AC incoming Earth Lead interrupting any galvanic circuit and is bonded at the same point as the DC ground on the Boat.

It should be noted that earth bonding a legal requirement to ensure safety. It is not only illegal, but also dangerous not to bond AC Earths to metal parts and DC Negative on Board. A common earth point should be used.