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Galvanic Isolator for battery charger

Old 12-27-2015, 09:31 AM
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Default Galvanic Isolator for battery charger

Setting up a very simple shore power system. Basically all it will do is to run the battery charger and a low wattage heater. ABYC says I should have a galvanic isolator for the system - at between $200 - $300 for two diodes and a capacitor (but that's another rant).

Would an isolator really be needed in this simple setting?
Old 12-27-2015, 10:01 AM
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A Galvanic Isolator is used to minimize electrolytic degradation of underwater metal. I was not aware that ABYC had any requirements for that. The reference may be to a GFI which would disconnect the charger in the event of AC voltage leaking into the water.

You probably don't need a Galvanic Isolator for your setup.

If you are using a portable automobile charger you would not need one since they typically do not have a ground connection from the AC cord to the DC negative so there is nothing to block.

A marine grade built-in charger will probably have the AC and DC grounds connected but again you only need a Galvanic Isolator if you are experiencing rapid zinc deterioration or signs of electrolysis on underwater metal.

You can get a 50 amp Galvanic Isolator for under $100 if you decide you need one. (Its actually 4 diodes, not 2, to give 1.2 volts isolation in both directions.)

It is rare that you need the capacitor. At least install the isolator first and then measure the AC voltage across it. You only need a capacitor if that reading is greater than about 0.5 volts.
Old 12-27-2015, 05:16 PM
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Thanks. I'm thinking I'll hold off for a bit and see what voltages I end up with. Where do you see an isolater for $100?
Old 12-27-2015, 09:46 PM
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Originally Posted by ColdWetDog View Post
Thanks. I'm thinking I'll hold off for a bit and see what voltages I end up with. Where do you see an isolater for $100?
http://www.amazon.com/YANDINA-Galvanic-Isolator-50-Amp/dp/B0166GXN6E/ref=sr_1_3?ie=UTF8&qid=1451277849&sr=8-3&keywords=Galvanic+Isolator http://www.amazon.com/YANDINA-Galvanic-Isolator-50-Amp/dp/B0166GXN6E/ref=sr_1_3?ie=UTF8&qid=1451277849&sr=8-3&keywords=Galvanic+Isolator
Old 12-28-2015, 12:03 AM
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Automotive battery chargers are a common cause of corrosion in boats, particularly small boats without shore systems. Auto chargers often provide no isolation between the ac and dc windings and can energize the negative terminal, which also energizes the boats grounding system. Portable auto chargers should not be used on boats, and are a frequent cause of stern drive or outboard damage.

Just buy a galvanic isolator and do it right. I prefer an isolator that has a fail safe mode.

Adding a shore power distribution panel and adding a galvanic isolator is really the right thing to do.

This is an excellent and inexpensive option. It's really a great, simple setup.

http://www.ezacdc.com/boat-wiring-pr...l-shore-power/
Old 12-28-2015, 11:14 AM
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I take it you are associated with the company. How do you manage to put together something at half the price of the other companies?

And who does your web site? They should be shot.. Orange is NOT the new black. Any info about your company?

tx
Old 12-28-2015, 03:37 PM
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Although the focus is on galvanic isolators, there is still a physical connection to shore and diodes do have a reverse leakage current.
No one can dispute the only way for complete isolation from shore is via an isolation transformer which only has magnetic coupling.
Old 12-29-2015, 05:09 PM
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I agree with your statement, but Installing an isolation transformer would be large money for this application.

I understand how Iso transformers work, have them on my boat, but I didn't realize the galv isolator had this negative. I suppose I could google it, but I can't visualize what you are describing.
Old 12-29-2015, 06:07 PM
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Originally Posted by ColdWetDog View Post
I take it you are associated with the company. How do you manage to put together something at half the price of the other companies?

And who does your web site? They should be shot.. Orange is NOT the new black. Any info about your company?

tx
Geez wet dog. Whats your gripe with Yandina? You're complaining about cheap pricing? The web site looks fine to me ,especially with the links to the product manuals.
Old 12-29-2015, 06:11 PM
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Let's keep this in perspective. One of the reasons people choose not to use an isolation transformer, is they are very very heavy at nearly 70 or 80 pounds apiece! Of course the price is equally prohibitive. So that may factor in their too.

You know most galvanic corrosion occurs below A volt and a half, so I see no reason for most people, due to the relatively inexpensive cost, not to pick up a galvanic isolator. To have nothing is absolutely crazy! Unfortunately I've seen that too.
Old 12-29-2015, 06:56 PM
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Originally Posted by ColdWetDog View Post
Setting up a very simple shore power system. Basically all it will do is to run the battery charger and a low wattage heater. ABYC says I should have a galvanic isolator for the system - at between $200 - $300 for two diodes and a capacitor (but that's another rant).

Would an isolator really be needed in this simple setting?
So, full disclosure here, I am totally not an expert on this topic. But, I may be in a similar situation so I have to ask this question. Is your boat kept on a lift or in the water? If the answer is on a lift, i THINK (but don't know) that your need nothing other than a "smart" or "computer controlled" on board 3 stage battery maintainer product. I am more than willing to be "schooled" and corrected if I am wrong.
Old 12-29-2015, 08:29 PM
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Originally Posted by CME View Post
Let's keep this in perspective. One of the reasons people choose not to use an isolation transformer, is they are very very heavy at nearly 70 or 80 pounds apiece! Of course the price is equally prohibitive. So that may factor in their too.

You know most galvanic corrosion occurs below A volt and a half, so I see no reason for most people, due to the relatively inexpensive cost, not to pick up a galvanic isolator. To have nothing is absolutely crazy! Unfortunately I've seen that too.
ColdWetDog never advised
1 what the voltage is
2 whether 4 wire split or poly phase connection is applicable
3 whether the 'setting up simple shore supply system" was to be on board or on the dock.

The use of a transformer is mandatory in many Marina's in Australia, so there is no choice and many Marina's provide them on shore at each berth or require a vessel to have one fitted before allowing it to be berthed.
Although I accept your comments per se, a GI is connected in line with the protective earth raises safety issues that also need to be considered, not just corrosion.

Nothing wrong with using a Galvanic isolator as long as you also have a GFCI to test it with and aware of it's limitations and risks of shorted or open diodes and off spec capacitors preventing required low impedance to trip CBs and safety switches. You do after all get what you pay for.
Old 12-30-2015, 07:58 PM
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Originally Posted by CME View Post
Automotive battery chargers are a common cause of corrosion in boats, particularly small boats without shore systems. Auto chargers often provide no isolation between the ac and dc windings and can energize the negative terminal, which also energizes the boats grounding system. Portable auto chargers should not be used on boats, and are a frequent cause of stern drive or outboard damage.
Does this apply to boats on a lift and those on the hard for winter storage, or in a garage on a trailer?
Old 12-30-2015, 09:39 PM
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Originally Posted by Karl in NY View Post
Does this apply to boats on a lift and those on the hard for winter storage, or in a garage on a trailer?
I think CME is referring to primary and secondary windings, the terminology "DC windings" as you know don't exist, well it does... it's called a 'short circuit', but all jokes aside it is an assumption that the OP is considering using an old technology 'transformer' type charger so I doubt the comments re corrosion is relevant.. Better to use a switch-mode multistage smart charger.
Regarding corrosion of transformer chargers, once the AC gets to the diodes its pulsating DC but the battery acts like a big smoothing capacitor so no AC is present at the battery except maybe some small ripple voltage on a fully charged battery, and even if there where, what was lost on one half negative cycle is sucked back on the other half positive cycle. DC is the problem not so much AC.
Old 12-31-2015, 09:06 AM
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Originally Posted by ColdWetDog View Post
I take it you are associated with the company. How do you manage to put together something at half the price of the other companies?

And who does your web site? They should be shot.. Orange is NOT the new black. Any info about your company?

tx
Yes, I started Yandina about 1991, in business 25 years although only on the Internet since about 1993. The business started on our boat while living aboard for 14 years http://www.yandina.com/boatPict.htm until it needed more space and employees.

Half price trick is a trade secret but they pass all ABYC tests except for the requirement (added long after we were in production) that it should have a remote monitor visible to the operator. The monitoring requirements are somewhat vague and unnecessary in my opinion. Every one we sell is tested to full ABYC specifications and although they carry an UNCONDITIONAL warranty we've not had a single return in 20 years.

I wrote the web site program including shopping cart back about 1993. It ain't broke and I've no plans for FIXING it. No fancy graphics but fast loading and functional. Customers rarely come window shopping, they usually know what they are looking for so we don't need no fancy video introductions .
Old 12-31-2015, 05:17 PM
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The problem is that because the GI is in the earth line, a short circuit from the active to the earth onboard, will pass an infinite current limited only by the impedance of the circuit components. Those components being the cable, switches, terminals and the Galvanic isolator. The overload circuit breaker will trip instantly for say a 1000 amp fault current but it is a mechanical device and compared to the semi conductor diodes in a Galvanic Isolater, is extremely slow. The diodes are rated in watts and can pass amps and can go either short or open circuit when fault current passes through them and this is why after an event that trips a circuit breaker on shore, GIs should be tested as it has operated as a surge arrestor and may no longer provide a protective path to earth leaving maybe, only the capacitor reactance of which at 50HZ should less than 0.02 ohms. The monitoring device enables confirmation that parallel components of 4 diodes in parallel with a capacitor are still functional.
Old 12-31-2015, 05:37 PM
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Originally Posted by isitstuffed View Post
ColdWetDog never advised
1 what the voltage is
2 whether 4 wire split or poly phase connection is applicable
3 whether the 'setting up simple shore supply system" was to be on board or on the dock.

The use of a transformer is mandatory in many Marina's in Australia, so there is no choice and many Marina's provide them on shore at each berth or require a vessel to have one fitted before allowing it to be berthed.
Although I accept your comments per se, a GI is connected in line with the protective earth raises safety issues that also need to be considered, not just corrosion.

Nothing wrong with using a Galvanic isolator as long as you also have a GFCI to test it with and aware of it's limitations and risks of shorted or open diodes and off spec capacitors preventing required low impedance to trip CBs and safety switches. You do after all get what you pay for.
It is a very basic setup - 110V, single phase, no other options available at the part of the marina where the slip is located. All I'm doing is running a shore power line to a battery charger and a low wattage heater that keeps it from precipitating inside. No inverter, microwave, TV or other amenities (it's only a 22') Boat is kept in the water most of the year - gets pulled only for maintenance in the deep winter (like now).


I'll probably go ahead and get an isolater (the outlets are GFI) - its' been an interesting discussion as usual.
Old 12-31-2015, 05:39 PM
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Originally Posted by yandina View Post
Yes, I started Yandina about 1991, in business 25 years although only on the Internet since about 1993. The business started on our boat while living aboard for 14 years http://www.yandina.com/boatPict.htm until it needed more space and employees.

Half price trick is a trade secret but they pass all ABYC tests except for the requirement (added long after we were in production) that it should have a remote monitor visible to the operator. The monitoring requirements are somewhat vague and unnecessary in my opinion. Every one we sell is tested to full ABYC specifications and although they carry an UNCONDITIONAL warranty we've not had a single return in 20 years.

I wrote the web site program including shopping cart back about 1993. It ain't broke and I've no plans for FIXING it. No fancy graphics but fast loading and functional. Customers rarely come window shopping, they usually know what they are looking for so we don't need no fancy video introductions .
Thanks for the reply - I've always wondered why the things are so expensive given that the circuit is anything but complicated and even high quality components aren't that expensive.
Old 12-31-2015, 05:56 PM
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Just buy this and be done.

http://www.ezacdc.com/boat-wiring-pr...l-shore-power/
Old 01-01-2016, 09:14 AM
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I just purchased a Dual Pro PS2 dual bank charger for topping off the batteries while at the marina. I wet slip my boat. Will I need a GI for simple battery charging?

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