Last week while I was traveling Leo wrote in with a good question about his boat's battery. His query came from a statement I made some ten years ago when I wrote the updated edition of the book shown here:

By the way, you can get your own copy of this book or any of my books by clicking on the Amazon.com link at the lower left side of this page. Once at the Amazon site, click on Minor Brotherton's name to get this book.

Ok, so now that I've made the shameless plug to try and sell some more books, back to Leo's good question.

Basically Leo wanted to know why I've said that it's not such a great idea to leave your batteries hooked up to a trickle charger all winter while they are out of service. Besides it being a waste of electricity, depending upon the charger design and its specific output characteristics you run the risk of just boiling the battery to death. His point to me was that the risk of boiling is low if the current and voltage outputs from the chargere are quite low. His concern is plate sulfation.  I have written about that issue here and a review of several earlier posts is probably in order, so check these two out to get a feel for all of my thoughts on this topic:

http://www.edsboattips.com/maintenance-a-diy/242-putting-the-battery-to-bed  and:

http://www.edsboattips.com/maintenance-a-diy/218-pulsetech-seeing-is-believing

OK, so here's my regimen for batteries. I now use one of the Pulsetech Extreme chargers in the fall and charge up both of my batteries to 100%. The Pulsetech approach takes care of any sulfation issues and I must reiterate that I've extended my battery life two-fold uing these chargers on a variety of my boat's over the last ten or twelve years.

Once the batteries are fully charged I disconnect I turn off my battery master switch. My parasitic loads add up to milliamps so I don't worry too much about them, but every boat is different so a mid-winter recharge is sometimes in order. alternatively, you can simply disconnect the batteries completely and leave them in place, but remember that any of your electronics that have memories needing power are going to have to be re-programmed in the spring.

The days of leaving batteries of any variety on charge all winter are way behind us. 

Received a question from a reader the other day regarding wiring connections found in the bilge area of their new boat. Simple question, how do I minimize the risk of the wiring connections shown in the photo I sent in to you from getting all corroded over time? The stud you see is a keel bolt on my boat, so the wiring is sitting in the bilge.

Bilge wiring such as you see here is vulnerable to corrosion

This is a good question and one we receive fairly often. I've tried a lot of products over the years to help minimize corrosion on electrical connections on my various boats. Without a doubt my favorite is Boeshield T-9. All of my exposed bus bars, terminal strips and stud terminations such as the ones shown above get a spray of Boeshield. I like it because it dries to a non-greasy coating that is transparent. That way when and if corrosion does eventually begin to for on the connections I'll be able to see it and deal with it before it becomes any problem. Boeshield is an aerosol and is available at just about all marine supply stores. Get a can and keep it on board. Its really a great product in my opinion.

Typical hull potential test set-up

We received an interesting comment regarding our earlier post, "To Bond or not to Bond". It's worth sharing so that people will understand some of the dynamics involved with that case. So, here is the comment:

Ed- "The comment I have on this situation is that given the original installation was done poorly, what is to guarantee the addition of a bonding cable would have been done any better? Regardless of how it was installed (bonding or no bonding), for my money, I would have expect that testing with a silver/silver - chloride cell being thrown over the side was done to make sure there was nothing amiss. A relatively simple and relatively cheap task given the risks.

In a similiar situation and a previous life, I demanded that a megohm test be done on all cabling pulled through metal conduit to make sure that the insulation on the cabling was still intact. I was burned once and doing this testing afterwards never let me down again.

To my knowledge, there is no type of QA checks like this in the ABYC standards. Should something like this be considered or have I missed it?"

Thanks,
Ken

So, let's walk through this step-by-step. First of all, many of you may not be familiar with what Ken is referring to when he mentions the silver chloride cell. In the photo above the black cylinder at the end of the long red cord plugged into the multi-meter is a silver chloride reference cell. Many corrosion analysts use these cells to provide a constant and reliable sensor for detecting low level milli-volt readings with the meter. The cell is put into the water the boat being checked is sitting in and plugged into the "com" lead socket on the meter. The + lead on the meter is connected to the boat's grounding system. The meter gets turned to the DC volts scale and a reading of hull potential is measured. This potential reading is an indicator of whether or not the boat is equipped with enough anodes to protect the underwater metal on the boat. It's important to note that the acceptable readings will vary depending upon what the anode material is made of, either zinc, aluminum alloy or magnesium alloy, and what the salinity level of the water the boat is floating in. Keep in mind here that this is all a measurement of galvanic level voltage potentials. Typically 1.6 VDC or less.  Now in the case we are discussing here, there was a situation where battery level voltage potential was leaking out through the light fixture. So, would that have shown up if the boat had been checked prior to the boat being delivered to the customer? Yes it might have as long as the light was activated at the time of the test. But to Ken's point that this should be a routine test that a boat builder performs as part of a general quality assurance test, that may not be practical in the real world. Let me explain why.

The actual hull potential reading for a boat is going to vary depending on a variety of environmental factors including water salinity, temperature and water flow (tidal currents). So, to be accurate, these tests need to be made in the location where the boat is going to be spending most of it's time in the water. In most cases, the boat builder has absolutely no idea where the boat is going to end up living, so precise levels of cathodic protection (what we are talking about here) are difficult to achieve at the factory. So in my view, cathodic protection levels really should be part of a delivery inspection once the boat arrives at its home port. I don't know of any builder that actually does this. Most builders install a few anodes on the boat in the usual places and hope for the best.

As for Ken's thinking that questions whether or not bonding the subject boat would have made any difference in the first place, I can say definatively that had the boat been bonded in this case, the boat would have been saved.

As to whether the ABYC has QA test requirements within it's standards at all, yes we do. ABYC standard H-24 for example, requires a boat builder to pressure test every gasoline fuel system as installed to ensure that no leakage is present.

You see, the ABYC standards are generally classified as safety standards. So, this begs the question about what constitutes proper levels of safety. Ken is quite right that we require no such broad based safety checks for electrical systems as installed. In this case, the fellow that bought the boat which sank was intending to do a lot of offshore sport fishing. If the light fixture had failed while he was motoring along 30 miles offshore and the boat filled up with water and sank, that's a potentially horrific safety issue in my view. But, I can tell you that in my time sitting in on electrical committee meetings with the ABYC, I've never heard this issue brought up.

Finally here, to Ken's mention of megohm tests for boats. Again, for those of you not familiar with such testing, this type of test is used to test the integrity of electrical insulation and involves shooting a pretty high voltage through the system and determining if there are any breakdowns in electrical resistance or insulation that could cause a problem. In commercial boating environments, this procedure is actually a requirement as part of periodic inspections. It is really quite an involved procedure to perform a comprehensive megohm test on a modern boat's electrical system. Statistically, I can tell you that the number of system failures like the one described in "To Bond or Not to Bond" is so small, that in spite of the severity of that situation, the number of actual incidents like it in a given year are so small, I could never sell the concept of a required megohm test or cathodic protection level test to the committee that governs these things. Plain and simply, there is not enough of a demonstrated needs for such tests.

Every now and then the topic of bonding a boat's underwater metal comes up. Sometimes pretty heated discussions can get going among the marine systems geeks that get interested in this topic. In any event, its worth sharing some insight into this topic with all, especially in light of my post last week that discussed the poor fellow's new boat that sank due to an issue with electrolytic corrosion.

When we talk about a bonding system on a boat we are discussing a system, usually made up of minimum 8 AWG wire and or copper strap that interconnects all of the underwater metals and also large metal objects on board like metal fuel tanks and such. The system can also become integral with a cathodic protection system. This all gets tied into the boat's grounding system. A line drawing, which comes from the ABYC Electrical Standard E-11 is shown below and it illustrates all of this inter-connection.

The area to focus on here is the lower portion of the diagram where you see the zinc (think anode, it may actually be made of aluminum alloy or even magnesium in fresh water). You can also see bits of underwater metal, like seacocks and such tied into this system.

The system is also tied into the boat's grounding bus and ultimately the boat's AC and DC grounding bus bars. Which are connected to the boat's battery(s).

The idea here is simple, but really does confuse most people. It all boils down to a basic electrical fundamental that states that if there is no difference in potential (think voltage here)from one point in an electrical circuit to another, then there can be no electrical current flow. Well, with that thought in mind, if all the metals are tied together via the bonding system, then they become equalized electrically and even if there is an induced ground fault leak from the battery as happened in my underwater lighting case, if all the connected bits of metal are at the same electrical potential then there will be no current flow. No current flow= no corrosion of underwater metals.

The bottom line here? The underwater lights on the sunken boat had not been bonded. Current leaked right out of the fixtures into the water and found an alternative path back to ground, actually via a nearby transom anode in this case. The anode was connected to the bonding system, and ultimately the batteries on board. The bonding system brought the fault current back to its source. Unfortunately it took out the light housings as a part of the process in this case.

Today's installment is a sad one. Its the story of a brand new boat, the buyer's dreamboat if you will, that sank in its slip about 1 month after he took delivery. The photo below shows the hole in the boat that caused the sinking.

Hole where under water light fixture was fitted

The white ring you can see around the perimeter of the hole is where the flange for the fixture was fitted. The white stuff is the 3-M 5200 used to seal the fitting. So the question is, where's the flange and the light?

This my friends is a sad tale of electrolytic corrosion, or to most people, stray current corrosion. This is of the DC variety and I can tell you that what you see here did not take to much time to occur. Although we can't be sure of the exact amount of usage on the underwater lights, what I can tell you for sure is that whenever they had power to them there was also a low level short circuit from the DC power feed to the light that was touching the bronze housing for the light. Why? Simple, the installer did not use an insulated terminal. But further the inside of the housing was not provided with any insulation by the light manufacturer, it was just nice raw bronze, totally uninsulated.

I can also tell you that the light was of the halogen variety and was therefore rated at a fairly high DC current, a little over 8 amps to be exact. So, what was going on here is that whenever the light was turned on, a portion of that electric current was exiting the fixture through the flange of the light, forcing the flange to act as an anode. The bottom line? The flange face simply fizzed away un-noticed and ultimately popped off. The light fixture then fell backwards inside the boat and the rest is history. This fellow's $400 K dreamboat sank in its berth.

So what's the lesson here? Make sure that there is no way possible for the power lead or terminals supplying power to any underwater light fixtures can come in contact with one another. That point of contact is a guaranteed recipe for disaster!