Power Leaking and Electrolysis...

[svHyLyte]

Hopefully one of you electric's wizzards can offer some help....


We have a Link 10 (aka E-Meter) on our boat that we use to monitor the starting battery. The unit was installed in March 2002 and seemed to work fine until about a year or so ago when we began to see a constant amperage drain indication of approximately .3 to .4 amps. Negative amp-hours would accumulate and in short order the meter would indicate that we had less than 50% of capacity remaining although the voltage reading seemed unaffected. Upon asking our “Expert Electrician” (who had installed the unit) about this, he indicated that the unit had simply “lost its mind” and came over and “reprogrammed” the unit. In short order, however, the problem repeated itself.

After several visits, Expert Electrician insisted the problem was in our batteries—which were only two years old—which he replaced at no minor cost. With the new batteries the problem repeated itself within days. He then claimed that the unit again needed be reprogramed, to no avail, and next that the unit itself was using the power--.3 amps? When another friend had a look at our wiring, he discovered that moving one of the wires to the Link 10—black with an in-line fuse—would cause the display to begin blinking. Hitting the “Sel” button would stop that and return the display to 4-Green Bars (regardless of the indicated status of charge prior to the blinking business).

This past week we had our boat hauled out for a bi-annual bottom paint and discovered significant electrolysis damage to our prop-shaft (which had to be replaced), our prop (newly installed 2 years ago) and the strut that supports the prop-shaft. This damage tells me that there has been significant power “leakage” somewhere which I suspect has come from somewhere in the battery circuit that the Link 10 has been announcing. Is this likely to be a correct assumption? Is there any possibility that powering the unit from the battery that’s being monitored is likely to show .3 to .4 amps of drain?

The starting battery circuit goes from the starter battery to an On-Off switch and then to the starter. There is a hot connection to the house batteries through a solenoid controlled by an intermittent switch on the engine instrument panel (in case the starting battery dies but we still have power in the house bank). There is another hot connection to the house bank through an isolator so that when the engine is running our high output alternator—which connects to the house batteries—will recharge the starting battery as well as the house bank. The last hot connection to the starting battery circuit is an Echo Charger line from a Heart Freedom 20 Charger/Inverter.

As an aside, our Alternator regulator is a Heart “Smart Regulator” that works in tandem with a Link 1000 that is set up to monitor the house batteries (4 Trojan T-105’s in two banks). Lately I have noticed that with the throttle in any set position, the engine RPM has been bouncing up and down (as has the Tachometer from zero to whatever) indicating that the Alternator is being activated and deactivated at high frequency.

Any assistance with this will be appreciated.


s/v HyLyte

[GordMay]

I believe you are on the right track in suspecting a phantom drain. Possibly a high-resistance ground (as opposed to a dead short) somewhere.

“...discovered significant electrolysis damage to our prop-shaft...”
and
”...significant power “leakage” somewhere which I suspect has come from somewhere in the battery circuit...”

[Rick]

The Link 10 can only "draw" between 25 mA and about 120 mA, depending upon ambient light and model so that is not the problem.

Verify that the black wire to the Link 10 is placed back where it should be according to the Link10 installation guide. (attached to a lug stacked on TOP of other lugs on the battery side of the shunt) and NOT to one of the shunt sense lead screws.

Verify that NO "sneaker" wires are attached to the start battery negative or to the other end of that cable going to the shunt. ALL other negative wires (other than the Link10 "black" wire) must be attached to the "load" side of the shunt.

So far, I'll guess that these checks have found nothing amiss, yet must be covered first.

Disconnect/reconnect the alternator positive wire and the field wire observing the Link10 for any change to the 0.3A drain. Continue on with this process disconnecting/reconnecting the starter positive cable, the Echo charge positive wire to the start battery, and any other positive wire that you can trace to the starter battery positive terminal always looking for any change in the Link10 reading.

Best bet: There IS a current passing through the engine coupling to the shaft causing your problems. This "leakage" current may be from the alternator internal diodes or an alternator field current brush or assembly, or perhaps some other wire attached to the engine block (from where?). By restricting, at first, your investigation to all wires leading to the engine you will probably find the culprit and trace it back from there. Note whether or not there is any "wet" sulpheric acid path from the battery positive or starter positive terminals to the engine negative anywhere.

Next: after you find the problem PLAN on attaching a shaft brush with a wire attached to your bonding system. Plan out your bonding system.

To dectect any future problem before this happens again buy a silver/silver-chloride "half-cell" sensor and use a good DVM to measure the half-cell voltage relative to your shaft to KNOW that the shaft is protected by a zinc. You merely drop the half-cell over the side running a long wire down below to the DVM near the shaft to make the measurement every month. Log in the voltage values to note the normal trend of the zinc degradation: i.e., like, 870mV, 820mV, 790mV "protected", etc. When you observe anything below 400mV you are in potential (pun indended) trouble.

[Rick]

You may have to remove all "ground" connections from the engine in order to reveal shore power or onboard neutral bonding or external dd(other vessel) influences on your vessel. If you do not have an ac isolator or if you have a generator or inverter with a neutral bonding connection made (when it should not be made) underwater metal removal may occur via engine block connections.

[EngNate]

YES, Stray current from somewhere in your boat's electrical system has caused the damage - assuming that your boatyard people have distinguished the appearance of electrolytic from galvanic corrosion. Electrolytic leaves heavily eroded areas with lots of pitting, dimpling and rough surface. If the boat is still out, I would not put it back, except to test/diagnose/confirm solved. If it is already back in the water, you need to work on it right now. Download & print the attached pages, then:

Get a Digital Voltmeter - even a <$10 one will do, and buy a 3/8" pencil zinc, without the plug (for engine heat exchangers). Drill a hole in the end and use a 40 watt or larger soldering iron to solder a length of wire to it. (Use patience & allow plenty of time for the iron to heat the zinc before putting solder to it.) Use filled heatshrink tubing of several sizes to fully seal the connection. Also get a piece of Scotch-Brite, and use it to clean the oxide from your probe before each session of use. Be sure to make a secure connection between your probe and the meter lead, and to get a good contact with the other lead to the part(s) being tested.

The information on the diagrams is simplified and should be fully self explanatory. With the above in hand, you can readily determine whether your underwater metals are happy. The information is intended to apply to non-metal hull boats protected by direct-bonding (no controller, e.g. Electro-Guard, installed), with bronze & Stainless underwater parts. Don't overlook the AC voltage check, and turn on all accessories & appliances, AC and DC, respectively, for each test. Everything need not be on at the same time, just checked. Check all AC devices when doing the AC voltage tests, and all DC devices when doing the DC tests. If everything is right, no AC voltage should be present under any conditions. (A few millivolts may be detected by the meter from ambient magnetic fields.) On the DC Galvanic test, no DC device should change the reading by more than a couple millivolts, except the starter, which could be allowed up to 100 millivolts.

Now, here's what I've found more than a couple times on diagnosing a boat with your same troubles: Poor integrity in the ground (really B-) path between the alternator and battery(s). In particular, a poor Bat - connection at the engine block can cause a significant voltage drop as alternator current passes through it under high loads. With a high output alternator, this can easily be so even though you may not notice that your starter is not up to snuff. The voltage loss in the connection is imposed on the engine with respect to other underwater parts that are connected directly to B- through the bonding system. (The strut damage is quirky, unless there's a good connection from it to the engine, and a bad or no connection from it to the rest of the bonding system.) With high output alternators it is good practice to run a B- wire from the alternator case (most provide a stud) to the B- ground buss. When testing your underwater metals, be sure to check with the engine running with some rev's and a good load on the alternator (remember, battery charger off for that test).

When looking at DC electrolytic corrosion problems, remember: "Anodes Corrode". With an externally-applied current (the distinction between electrolytic and galvanic corrosion), the damage is done to the part with the positive potential applied. It doesn't need to be +12V, just higher than another part nearby. Thus, the poor B- connection at the engine block, with alternator current going through it, gives the block a positive potential, which will be passed to the shaft and prop unless an isolation coupling is installed. For the small amount of current that you are seeing 'lost' to create a significant voltage potential at the engine, there would have to be practically no ground connection at all (Possible if you have an isolated starter, normally reserved for metal hulls).

When troubleshooting this problem, ignore the Link and go about it as though it weren't there. The current it's showing may be your stray current and it may be not. Rely on the meter and probe, as it is a direct-read on what's happening with your metals. Turn off and disconnect things - everything - until you find the source(s) of your troubles.

It must be stressed that good wiring practice is essential to prevent corrosion problems and minimize the effect of faults when they occur. A proper B-/Bonding/AC Safety Ground layout is critical, and I'll try to put something together on that soon.

Incidently, when reading the Link Amps or AH, be sure of the sign displayed. A minus shows for Amps going out or AH down. If your battery is 50% down, there should be only 2 of the 4 LED's lit, and below that the remaining 1 or 2 LED's will be amber. If a charger is connected and on, a positive AH reading will accumulate after the battery is fully charged. The value is normally meaningless, and as soon as the 1st Amp-Hour is drawn, it dumps the accumulated value. Multistage automatic chargers will cause fewer AH to accumulate than older models. An excessive accumulation in a short time indicates a bad battery (shorted cell(s)), or charger voltage too high.

NEA

I thank all that have participated on this thread. Great information. I had a leak last year and found a high resitance grounding at an engine panel ameter. The insulation failed at the back. Ignoance can make you edgy, I'm still not satisfied I have all under control. I'll be applying some of the advice here.

Thanks again

[svHyLyte]

Gordo, Rick, EngNate et al..

Thank you all for taking the time to respond. A lot of food for thought although I must be candid in that some of it is over my head. I am a structural engineer rather than electrical so my knowledge of electric's is rudimentary at best. I am printing out your responses to take up to our boatyard for discussion with our yard guys--Snead Island Boat Works, in Palmetto, Florida. In the case of electric's, as opposed to the usual male practice, I follow written directions very carefully (if it says insert a fuse within 7" of the positive terminal--I do!). My one major concern with resolving this issue is that our boat yard uses "Expert Electrician" (which is how we got involved with him to begin with) so I'm wondering how likely it is that he'll discover--or reveal if he does discover--his own error. (This process may also be further complicated by the fact that we do have a 4.2kw generator aboard as well as a 2kw Heart Inverter--tho' neither are used much.)

At this point the boat is still out of the water while we await the delivery of a new 30mm prop-shaft from Beneteau. The damage to the shaft was erosion and pitting as described by EngNate. At one point, right at the edge of where a zinc was attached to the prop shaft and between the zinc and the shaft struct, the pitting makes a perfect circle around the shaft approximately 1/16th in deep and about 1/8th of an inch wide. On the prop, the prop-blades look as though someone had been beating on the outer blade tips with a very small ball-pean hammer. And, the tops of the stainless pins in the prop literally looked like swiss cheese, although the shafts through the blades were uneffected.

We sent the prop over to Frank & Jimmie's Prop Shop in Ft. Lauderdale (recommended by Geoff a AB-Marine, the Gori dealer) where Larry Tarter examined it and fortunately concluded that the damage was only cosmetic. They're going to clean it up, rebalance the blades and machine new pins all for an estimated cost of only $150 (which seems like a pretty good deal to me, no?).

A friend that has the same boat a we has also recommended installing a Globe "DriveSaver" which I plan to order as soon as I can get the flange measurements.

Regarding the Alternator--one of the things that really concerns me is my discovery that there are several connectors emerging from the wiring harness for our engine--a Perkins 4-108--that are hanging loosely behind the alternator; and, an unequal number, also hanging loosely in the vicinity of the starter none of which are taped over or otherwise indicated as being out of service intentionally. (As my memory isn't that great, I usually attach plastic lables to things to remind me of what they are--or were. It may look a little silly, but when I have to come back to something in 6 months or a year, it's nice to be able to see that a loose wire is, for example, an "OEM windlass actuator pos. lead--abandoned in place"

N'any case, its early Sunday AM, the dog is scratching at the back door, and I can smell coffee and pots being rattled in the kitchen so I'll sign off. I will keep everyone apprised of our discoveries.

Once again, thank you all.

Scott
s/v HyLyte

[Rick]

Lots of good details from EngNate's notes above.

You might not totally ignore the Link10 indication of 0.3A discharge current as it is highly likely to be a valid indication (although as EngNate implies not necessarily the only one to look for) that the abnormal indication is due to at least some of it passing through the Link 10's shunt!

[Alan Wheeler]

Scott, the easiest way to understand electrical circuits is to think of it as a plumbing situation. The electricity is the water. The pressure is the Volts and the Current is the volume of flow. A leakage in an electrical circuit is the same. Water seeping to ground. It always wants to go back to the ground. The issue in your case though, is finding that leak. Your situation is one of complexity. You have a very complex systrem of pumps and pressure valves and flow valves and so on. The problem is, it is leaking from a "valve", not a hose connection. It is leaking back internally from a "flow control valve" or a "seal" somewhere. So you have to start isolating areas to find the faulting compnent.
See what I mean. Suddenly a lot easier to understand. Of course, it doesn't make finding and fixing the problem any easier.

[EngNate]

I rarely include judgement or criticism, as it's not a troubleshooting method, but 'expert electrician' is not, and probably a very poor value at boatyard rates. I don't usually sell myself (and I can't right now), but if I were there now, we'd have them set it in the water tomorrow morning, and before the end of the day I'd be gone with these troubles in my pocket. Anyway, if he's cooperative and understands and follows the directions and details thoroughly, you can leave there with your problem, at least that one, solved. The BY people should be eager to get hold of these techniques, if not, you need to find a better yard for the future.

Wires hanging that went to your original alternator but are disconnected now would be: Alt turn-on from key-sw or oil press sw; Voltage sense; Tachometer conn; Output wire to starter B+. The last should definitely be followed and disconnected at the other end, or better, removed. Insulate and secure the others if you don't want to remove them entirely.

Your shaft-saver coupling is a good investment regardless. As long as they install it properly & don't mess up the alignment you should enjoy a quieter, smoother ride under power. It will electrically isolate the shaft and prop from the rest of the boat and other boats, reducing or eliminating corrosion problems from a variety of faults. Remember, though, that previously a connection was made through the engine to the other underwater parts - and more zinc. If the shaft zinc was neglected or came off, the shaft and prop could get some protection from the plate zinc (fair at the dock, erratic to nonexistent underway). If the plate zinc was gone, dis- or poorly connected, or not 'burning' because of growth, the other parts would draw their protection from the shaft zinc & make it go away quickly. If neglected, the situation would result in more severe damage than yours. The reason to keep the point in mind is that your shaft & prop zincs will last longer - possibly much longer - but will be more critical because they are the only protection available. Don't ever let them go much beyond half the original mass. Don't install a shaft brush, except to connect to a meter. A connection to the bonding system will defeat your purpose for installing the coupling. Also, be careful about the shaft log & packing nut. There shouldn't and normally won't be any metal-to-metal contact, but there might be if things are out of whack. A dripless shaft seal may need additional consideration. The shaft log is normally connected to the bonding system, but the amount of protection it can recieve is limited to nonexistent (another topic).

If you have been putting more zincs on the shaft recently because of this problem, go back to the original amount or that reccomended by the boat maker. Ideally, fresh zinc should give a meter reading of about 80mv. (More in another topic later)

Since you mentioned the generator and inverter, and Rick noted re: shore neutral; Very important point, mostly for another topic, but there should be no connection between the AC Safety Ground and Neutral except at the power source - The transformer (on the land, dock or on the boat, but not autotransformers), generator, or inverter - when inverting. Inverter/chargers with automatic transfer relays handle this function automatically, but some (e.g.: Trace 4000SW, Outback) have a jumper connection which must be correctly observed. Generators and stand-alone Inverters must be connected to the system through switching that opens the neutral circuit along with the line(s). Same with a manual transfer switch installed with an auto inverter. Neutrals of multiple shore sources and load groups should be isolated the same way, and it is good and common practice to do so with a single shore line. One very common occurrence that causes a fault on 120/240V systems is the installation of a 240V domestic appliance such as a range or dryer. These typically come with a 3-wire cord and plug, and have a jumper or bonding screw connecting the neutral to ground. They use a small amount of 110v for accessories such as the light and clock. This is acceptable in buildings, but not on boats. You must use a 4-wire connection and remove the jumper. The most common cause of mysterious Hot Docks is the combined faults of a high resistance neutral circuit and ground-to-neutral connection(s) on one or more boats.

NEA

Before you judge a man, you should walk a mile in his shoes -- then you are a mile away from him and you have his shoes!!

[svHyLyte]

Everyone...

Thanks for your follow-up messages. I have printed out this thread and delivered it to Snead Island Boat Works. The job manager indicated it would be very helpful in their efforts to track down the problem. Frankly, I'd like to do it myself but once a boat is in the clutches of a boatyard...

N'any case, they were anxoius to get the boat back in the water but I indicated that they were to hold on that until the cause of the problem is discovered. I'll keep everyone apprised.

Cheers

s/v HyLyte

[Rick]

What is the agrument for not using a shaft brush under any condition? I'm missing something on what your recommended equivalent circuit might be where the shaft, prop, and zinc exist isolated from a rudder shaft, metal through-hulls, and transducers, etc so that everything can be protected from electrolysis.

[EngNate]

Read it again. Count each word and sentence, they all mean something.

"Don't install a shaft brush, except to connect to a meter. A connection to the bonding system will defeat your purpose for installing the coupling."

The shaft and prop can exist out there 'by themselves' because the coupling referred to is polyurethane and eliminates the electrical connection. There is no electrical contact through the cutlass bearing, nor to anything else, as long as you don't go put a brush on it and connect that to the bonding system. Parts must be electrically connected to 'participate' in the corrosion process. An isolated shaft has nothing to do with protecting "everything", but it does take those parts out-of-the-loop.

HyLyte - Following a comprehensive visual examination for potential faults, you will need to diagnose the trouble in the water. If your batteries are all disconnected and the shore cord is not plugged in, you can have no electrolysis, at least not from your own boat. Put it back in the water this way with no worries. They have a spot there for you dockside? Temporarily hook up a bilge pump direct to a battery, run some cords & lights off the dock, and proceed.

N

[Rick]

If HyLyte's boat only has shaft (and/or prop) zincs AND if the boat has metal through-hull fittings or other underwater metals the shaft should have a brush connected to a bonding system with all underwater metals connected, if possible.

All underwater metals ARE electrically connected via the conductivity of the water and, therefore, need to be kept to as close to the same potential as possible by a bonding system. That way a zinc has the best possible chance of protecting everything bonded together.

The ONLY thing that an isolated coupling does is to prevent any bonding current from passing through the engine and does not "buy" anyone much...probably a total waste of money because a shaft brush, if properly installed, will conduct the preponderance of bonding current (which allows the zinc to protect the underwater metals).

[colemj]

Originally Posted by Rick

The ONLY thing that an isolated coupling does is to prevent any bonding current from passing through the engine and does not "buy" anyone much...probably a total waste of money because a shaft brush, if properly installed, will conduct the preponderance of bonding current (which allows the zinc to protect the underwater metals).

Actually, I believe the purpose of the drivesaver is to provide protection from slight misalignments/vibration and as a "fusable link" in case of wrapping the prop or hitting something solid. The continuity isolation is simply a by-product of the design. Rebonding of the shaft to the engine is easily accomplished by jumping a piece of wire across the drivesaver bolts. This is discussed in the drivesaver installation manual.

Mark