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Rank: Advanced Member
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Joined: 12/20/2007
Posts: 38
Points: 114
Location: Lake Anna Virginia
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I have a question I am hoping one of the electrical gurus we have on the forum can help me with. I have a Charles isolation transformer and a charles batter charger in my 26' convertible. Mt elec panel is a Blue Sea.
There is a light on that panel that indicates if I have reverse polarity. Everything is fine until I turn on the battery charger. I notice the red reverse polarity glows on the panel, but not real brightly. Just noticeable.
Any ideas why this might be happening?
Also I am afraid to charge my batteries as I am wondering if I may be inviting corrosion issues. Would that also be a concern?
I am really stumped on this one.
As always, thank you guys....
Bob
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Please Register : New members may not post until approved. An email is sent after approval. We do this to reduce those who use these forums for spamming.
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Rank: Top Rank Aluminum Star
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Location: Central Florida and the DC area
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Bob,
The ac reverse polarity light tells you when there is voltage between the white neutral and the green ground. You should have none using an isolation transformer.
The dock power black and white connect directly to the primary of your isolation transformer, and the shield connects to the green. There is no connection from the dockpower to anything else.
The isolation transformer secondary should connect to the ac panel black and white, with white also connected to the hull. The green ground in the boat is connected to the hull. The galvanic isolator that came with the boat is not used.
You have voltage between white and ground when the charger is turned on. This cannot happen unless there is a miswire. Check the ac connections and make sure there is no mixing of power between shorepower and the ac panel. If you have a schematic, please post it.
"Anyone who has ever chanted "drill, baby, drill" please report to the bayou for cleanup duty..."
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Check to see if you have a bad diode in the battery charger. One that conducts both ways. --Ed
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Rank: Advanced Member
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Joined: 12/20/2007
Posts: 38
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Location: Lake Anna Virginia
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Big thanks for the help guys.
I am guessing I should hold off charging batteries until this is resolved as it could lead to corrosion issues ??
I am wondering if the diode is my first step since the reverse polarity light just showed up over the last month or so, and the boat / transformer has been in the boat for 3 years now (I should have clarified this, sorry) and seemed to be just fine with no indication of reverse polarity on the panel.
Doug, I will look for a schematic and post it if I can find it. Thanks so much for your continued help.
Bob
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Rank: Top Rank Aluminum Star
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On a similar but different vein, I was fortunate to resolve my battery over-charging problem. To wit:
For several years, water levels in the batteries were too low, so much that I was putting water in every few weeks (and it cost me at least one battery). After hearing someone suggest that I turn the battery charger OFF when I leave the boat--a good idea!--the water loss was lessened. So I replaced the old charger with a new, reconditioned and guaranteed unit--and many thanks to who suggested it here.
Problem resolved.
Jeff
"There is another class of coloured people who make a business of keeping the troubles, the wrongs, and the hardships of the Negro race before the public. Having learned that they are able to make a living out of their troubles, they have grown into the settled habit of advertising their wrongs -- partly because they want sympathy and partly because it pays. Some of these people do not want the Negro to lose his grievances, because they do not want to lose their jobs." Booker T. Washington
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Rank: Dedicated Tin Star
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Jeff,
I personally don't think that's a good idea. A bilge pump will drain a battery fairly quickly if it runs continuously. I had my battery charger breaker trip this summer (during an extended period when I wasn't able to get to the boat) and the by the time I got back to the boat the battery was dead and I had a fair amount of water in the bilge (from all the rain we had - normally my bilge is dry). Luckily the water wasn't high enough that it caused any problem anywhere, but I wouldn't leave the charger off - one hose failure could sink the boat very quickly.
Fred
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Rank: Top Rank Aluminum Star
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Agreed, but this was a carefully watched test.
For one thing, I had 3 fully charged batteries on line to run the bilge pumps. I know from monitoring the boat all summer, that it doesn't leak much (purely from the stuffing boxes), and my new rear cockpit deck is so water tight that the bilge below is dry for the first time in years!
Your point is extremely well made, however. Many an outdrive boat with a cracked bellows has gone down in the slip after the batteries gave out.
Jeff
"There is another class of coloured people who make a business of keeping the troubles, the wrongs, and the hardships of the Negro race before the public. Having learned that they are able to make a living out of their troubles, they have grown into the settled habit of advertising their wrongs -- partly because they want sympathy and partly because it pays. Some of these people do not want the Negro to lose his grievances, because they do not want to lose their jobs." Booker T. Washington
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Rank: Advanced Member
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Joined: 12/20/2007
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Location: Lake Anna Virginia
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Doug
Sorry for the long gap in reply. I am fairly certain what we did when we wired the boat we did not connect the ground and neutral from the panel to the hull. In fact we tried to isolate them from the hull. My question is this....if you connect the neutral and ground to the hull, and you have a reverse polarity situation, is the hull then not electrified? Sounds really dangerous considering I have aluminum cockpit decks as well! Please clarify as I think (and I need to check my notes) that I had checked with Bluesea before we installed the panel and they indicated that for an aluminum boat it should be kept off the hull. Finding my notes will not be easy as I save everything and there are reams of notes!
Now for a new revelation in this saga........before we pulled the boat last week we thought we'd take a fresh look at this issue. Now, and for the first time, I noticed the reverse polarity light come on for one of the other breakers not associated with the battery charger!! I then took a 110 volt polarity tester and inserted it into each of my 110 outlets. In each outlet the tester read aok, no reverse polarity....however, the Main panel would show reverse polarity (strong light this time, unlike the weak light when the battery charger was on). I am starting to think maybe the panel is bad. It sits right under the deck and although there is a plastic box around it, I know condensation and humid air get into that thing. What do you think?
Thanks for all the help
Bob
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Rank: Top Rank Aluminum Star
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Location: Central Florida and the DC area
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Your isolation transformer has two windings, a primary (dock) winding, and a secondary (boat) winding. There is a shield wire as well.
There should be NO connection from the primary to the secondary. There should be NO connection from the shield to either the primary or secondary.
The primary connects to shore power black and white. The shore power connects to nothing else.
The shield connects to shore power green. Shore power green connects to nothing else.
The secondary connects to the panel hot (black) and return (white) inputs. The return (white) also connects to the panel ground (green), which is usually connected to the hull.
If these connections are made, then there is no reverse polarity.
I would look carefully at the connections to the isolation transformer. I have seen several that were wired with the shorepower ground connected to the panel ground, eliminating all the value from an isolation transformer. The SeaRay plant (about 200 yards from my boat) cranked out many such miswirings once thanks to a bad production procedure, and there was a brisk business fixing them for a while.
"Anyone who has ever chanted "drill, baby, drill" please report to the bayou for cleanup duty..."
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Rank: Advanced Member
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Location: Lake Anna Virginia
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Thanks Doug
I know our 12 volt ground goes to the hull via the engine, motor mounts, stringers. The 120 volt from the tranny we isolated from the hull. What is the purpose of connecting the 12 and 120 volt grounds together to the hull? With the exception of the 120 volt grounding, we have it hooked up correctly. We even checked the ABYC guidance for hooking up iso trannys. I am still wondering now if we have a panel that got a little wet or most causing errant reverse ground indication.
Thanks
Bob
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Rank: Top Rank Aluminum Star
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Location: Central Florida and the DC area
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Connecting your 12 Volt return (not actually a ground) to the hull is something you are stuck with because the engine block is the return for all the engine circuits, and the block is connected to the hull. Most Marinettes seem to have a stud in the hull in front of and between the engines. Battery negatives go to the stud, and a heavy wire runs over to the block.
This is fine, but the preferred way is to run heavy wire from the starter directly back to the battery, eliminating the connection at the stud. In any event, the battery negative ends up connected to the hull.
You probably don't want to let the secondary of the isolation transformer (tranny?) just float. If the hot side shorts to ground (hull) then the neutral side will become hot and the breaker will not trip, both bad things. Most sources say to connect both the neutral (white) and ground (green) to the hull for proper breaker operation. This connects the metal frames of microwaves and stuff to hull for you via the green wire, and keeps the white wire near ground potential where it belongs.
Be sure that the dock power goes only to the primary side, with the green connected to the shield or frame. Be sure the dock power green is not connected to the hull. The whole reason to have an isolation transformer is so you don't have to have the dock power green connected to the hull.
Don't be concerned that the hull is being used for both dc and ac grounds. Just be sure that the connections are made at one spot only. For dc, that is probably the stud in front of the engines. For ac, it is the isolation transformer secondary white. The green to the outlets also goes to the hull.
"Anyone who has ever chanted "drill, baby, drill" please report to the bayou for cleanup duty..."
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