galvanic isolation / 12v charging

[srod]

I'm on mains hook-up most of the time and have a galvanic isolator in-line with the earth, the standard set up and this is all good...

 

Just use 12v for lighting and the pump, so I need to keep these topped up.

 

The boat's previous owner used a standard car batt charger plugged into the mains on the boat and connected across the domestic batts to maintain the charge, which seems fairly straight forward and works well.

 

However - I was wondering if this setup would cause unexpected stray currents, and therefore some galvanic corrosion on the hull? The battery grounds are bonded to the hull at various points, so connecting the ground of the battery charger to them is effectively making a circuit between the hull and the mains supply? Or would the 240/12v transformer provide enough isolation between neutral and ground?

[Keeping Up]

I'm on mains hook-up most of the time and have a galvanic isolator in-line with the earth, the standard set up and this is all good...

 

Just use 12v for lighting and the pump, so I need to keep these topped up.

 

The boat's previous owner used a standard car batt charger plugged into the mains on the boat and connected across the domestic batts to maintain the charge, which seems fairly straight forward and works well.

 

However - I was wondering if this setup would cause unexpected stray currents, and therefore some galvanic corrosion on the hull? The battery grounds are bonded to the hull at various points, so connecting the ground of the battery charger to them is effectively making a circuit between the hull and the mains supply? Or would the 240/12v transformer provide enough isolation between neutral and ground?

Assuming that everything is wired and grounded in the usual and correct way, connecting everything in this way is normal and should not cause any unwanted stray currents.

 

If the charger is a standard car charger, ie it is not intelligent, you would need to apply the intelligence yourself in switching it on and off at the right times. Either leaving it too late before you start charging, or leaving it charging for too long after the batteries are effectively "full", could reduce the life of your batteries. It may be worth investing in an intelligent (multi-stage) charger, which can then be left permanently connected; their cost tends to be repaid by extending the life of the battery.

 

 

(Edited for spelling)

Edited February 2, 2010 by Keeping Up

[WotEver]

I'm on mains hook-up most of the time and have a galvanic isolator in-line with the earth, the standard set up and this is all good...

 

Just use 12v for lighting and the pump, so I need to keep these topped up.

 

The boat's previous owner used a standard car batt charger plugged into the mains on the boat and connected across the domestic batts to maintain the charge, which seems fairly straight forward and works well.

 

However - I was wondering if this setup would cause unexpected stray currents, and therefore some galvanic corrosion on the hull? The battery grounds are bonded to the hull at various points, so connecting the ground of the battery charger to them is effectively making a circuit between the hull and the mains supply? Or would the 240/12v transformer provide enough isolation between neutral and ground?

Really? Various points? That will (potentially) cause galvanic corrosion all by itself. See if it's possible to create one single earthing point to the hull for all of the battery negatives.

 

Edit to add - "and what Allan said about the charger."

 

Another edit to say here's some info: http://www.smartgauge.co.uk/galv2.html

 

Tony

Edited February 2, 2010 by WotEver