Was asked about Chargers and Galvanic Isolators So Here Goes

A Case for Using Marine Chargers and Galvanic Isolators.

A 12m launch has been in the marina for many years. Up until recently it's never had a problem with galvanic reaction on its underwater metal surfaces.
As advised correctly by the vessel's electrician, the owner decides to install a battery charger to his battery banks. Unfortunately, against the recommendation from his marine electrician, the owner chooses to save a few dollars and purchase a cheapy car charger from one of those automotive supply stores that specialise in budget priced car accessories.
Now armed with this new purchase the owner decides to simply run a lead into the boat from his shore power plug on the dock and proceeds to hook the aligator clips on to the battery. All done he thinks and it didnt even require him to have one of those “fancy” 3 step chargers he was advised to get.
He couldnt be more over the moon than the next time he comes to the boat and finds he hasn,t got flat batteries any more.
Six months go by and the boat is scheduled to be hauled by the local yard to have the bottom cleaned and antifouled. After the boat is power washed and blocked in the yard a more thorough inspection of the hull reveals a serious problem! First to be seen is what looks like burnt paint around each of the bronze thruhulls and then closer inspection also reveals, shock horror!, the thruhulls are erroded till there is almost nothing stopping them from popping straight out. The propeller also looks like worms have been passing through the bronze metal in the blades and the bronze has turned pink in colour.
At this stage the electrician recieves a call to hot foot it down here and explain why the boat he looks after has had such severe electrolysis! After a thorough check with no culprit found a few questions are asked of the owner. He says the only change electrically that's happened is the battery charger that's been fitted, which was incidentally $150 less than what was quoted by the electrican. After a quick test it's discovered that this charger has a ground isolation fault inside it and has created a ground connection between the shore and the boat's ground.
The saving of $150 has now resulted in a costing of thousands of dollars and, had the erroded thruhulls popped inward while the boat was in the water, would have certainly resulted in a sinking.
It's difficult to understand why some things in the marine industry are so expensive but if you look below the surface (excuse the pun) there is often a valid reason. One of these things is the marine battery charger. They may look no different than that cheapy Chinese brand but they really are not designed to do the same job and consequently cost more to make.
For instance, they are all designed for 3 step charging because they are left on the battery indefinitely. They are designed to be electrically isolated from boat ground and shore power ground. And to some degree they also have conformally coated circuit boards for water resistant ratings. Some are totally waterproof!
In the USA the regulating body, the American Boat And Yacht Council, which is made up of people from the marine trades and coastguard, stipulate the use of galvanic isolators on vessels wired to the dock mains power. These units have been around for many years and although not widely used here are vital for protecting your vessel from electrolysis from your boat to the dock through the shore power ground. They essentially allow the ground connection to exist between the dock and the boat for 230V AC protection in case of accidental electrocution but blocks the DC connection that would result in electrolysis or metal loss between boat and dock so common in marinas.
I hope this has not confused too many however it's becoming more important to protect that expensive investment than ever before and with the increasing proliferation of shore to boat connections in marinas its important to make sure you're armed with the information to protect your investment.