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**EngNate** · 04-07-2007, 13:12

The Nigel Calder dude writes books, he doesn't fix boats for a living. And 'suggested' <> 'well documented'. I said 'field-proven'. Quit arguing and use the meter, you're going to love it, I swear.

brian and clare · 04-07-2007, 17:43

Hi, Not to get off topic here, but I have heard that the real danger of fittings getting eaten is through the 12 volt (or 24 Volt) DC chargers being left on, and stray DC current doing the damage. Im no electrician, and some of what has been posted makes my head swim, but it seems to make sense based on an episode of myth busters where one guy tried to eat through a metal bar using AC current (and salsa) and another tried it with DC current. AC did bubkis and DC Ate through the bar in short order. Any thoughts on this from the experts? Can anyone enlighten me?

PS - Mythbusters rules

B

seafox · 04-07-2007, 19:01

Quote:

what has been posted makes my head swim

You are right there.

All I know is I was chewing thru annodes connected to the shore power and with battery charger always on and without it connected the rate of anode chew has fallen to a more acceptable level (acceptable to me anyway

)

**Alan Wheeler** · 04-07-2007, 21:12

Quote:

I said 'field-proven'. Quit arguing and use the meter, you're going to love it, I swear.

First off, being a little less up yourself may go a way's around here. If anyone is arguing, it is you, so please be a little more cordial. This is fact and field proven. Up to you if you want to believe it or not. I'm not arguing.

Brian, if the charger is a proper marine one, as in it is Prim/Sec "isolated" and the boat is properly wired fro protection, then leaving it on will cause no issues.
I did not see that Mythbuster episode, but DC would chew through a bar faster than AC. This is because the electron flow is what is carrying the electrons of the metal along with it. Thus erroding away the metal. AC is alternating current. So the electrons flow one way and then back again. It's a little more complex than that in regards to speed of electrons and electrolyte and so on and so on, but that is mostly the nutshell.

southernman · 04-07-2007, 23:45

And can I add Alan that an isolating transformer is actually the best option rather than an isolated type charger. Many of the cheaper chargers so called isolation is not very good at all and only isolate the + and not the negative.

This is a very interesting subject and having owned a steel boat I did a lot of research. We see the 2 schools of thought here I guess on a very debated subject.

**Alan Wheeler** · 05-07-2007, 00:57

Absolutely Southernman. But most chargers with transformers now a days, are not a good boat charger. They are often very simple chargers. I could be wrong here, but I know of no "smart" chargers with Transformers. All are switch mode as far as I know. the only Transformer based chargers I know are cheap "trickle" chargers that quite frankly, are next to useless.

**EngNate** · 05-07-2007, 07:19

So, Alan, let me get this straight, You don't believe the meter and readings thing, and you're not going to even try it?? The world really is flat? I didn't come up with this on my own. Electro-Guard, the company that makes cathodic protection systems, used to hold a school on this, the predecessor to the current ABYC certification course, which they helped develop. I took that course years ago, and the principles have never once failed me. By field-proven, I mean I have seen the boats I've worked on over and over for years, trouble-free.

What type of battery charger you have is of no bearing on corrosion, assuming it is not defective. All marine battery chargers have transformers. Switchmode chargers use very small transformers that operate at high efficiency because of the high frequency. The incoming AC is rectified to DC at full line voltage, then switched on and off to feed the transformer with around 20K Hz. There may still be one or two 'Flyback' designs out there, these do not have isolation between the inupt and output, and though some have been sold under marine brands, they are not suitable for boats. Professional Mariner sold one, and maybe still does. Those designs also have more potential for shock hazzard when internal components fail.

If you have current leakage from your DC system, the battery charger will make things worse simply because it is increasing the system voltage by 10% or so. In the absence of a fault within your system, the battery charger has no bearing on corrosion.

DC stray current is much more damaging than AC for a given voltage level. The reason is twofold. First, only one end of the circuit, the one to which a positive potential is applied, will corrode. The AC is reversing polarity, so the affected parts are only exposed to the right polarity for half of each cycle. Secondly, there is inertia in chemical reactions, they don't begin instantly. The corrosion reaction barely gets started on each cycle before the polarity reverses. Thus, the net effect from AC current is far less than DC. It is however, taking place 24/7, not just for a half hour.

Folks, I'm just pushing one thing: Make and use the meter and probe setup I've described. We are debating in abstract, and this test provides hard values. With those, any one of you can prove or disprove for yourself any and every argument in this thread.

I'm arguing for techniques, not against any other person, so please don't take it any other way.

NEA

senormechanico · 05-07-2007, 20:04

Quote:

Originally Posted by Alan Wheeler

Absolutely Southernman. But most chargers with transformers now a days, are not a good boat charger. They are often very simple chargers. I could be wrong here, but I know of no "smart" chargers with Transformers. All are switch mode as far as I know. the only Transformer based chargers I know are cheap "trickle" chargers that quite frankly, are next to useless.

Switch mode chargers still have isolation, at least all the ones I've seen.

Even a laptop AC adapter (which is a switch mode power supply) has I/O isolation.

Steve B.

**Alan Wheeler** · 06-07-2007, 00:28

Exactly Steve. The inherent design of Switch mode means it has an isolated front end to aft end of power supply. I have repaired more SMPS than I have had hot dinners.

EngNat, please don't twist my words. I have not stated or implied anything about not measuring or believing a meter. Do not screw my words thank-you.
I could ask exactly the same question of you. So are you implying that you have not ever measured a voltage difference between two different boats, side by side, plugged into the same shore power??? And are you also saying that because you have not measured such, therefore such can not exist?? Am I understanding correctly??

seafox · 06-07-2007, 02:03

Quote:

I have repaired more SMPS than I have had hot dinners.

Geez Dawn, and you are a good cook too! What is wrong with your man?

**EngNate** · 08-07-2007, 16:55

[quote=Alan Wheeler]Hi EngNat, errr that's not entirely true.

[quote=EngNate]I have to counter Alan.

[quote=Alan Wheeler] If anyone is arguing, it is you, so please be a little more cordial.

In re: Being cordial: I think one of the first two above contains a just hint of personal jab, while the other limits its scope to the contradiction of views. (Quotes shown in chronological order)

Congratulations, Alan, on being the top poster on the site, you represent 5.6% of the view of this entire site, a ratio of 385-to-1. Please recognize one thing at least: A post such as my first reply in this thread is not just dashed-off in five minutes, it takes a lot of valued time.

Yes, indeed, I've measured boats side by side, and every boat on a dock, and stray currents and supply voltage drops all along a dock, and more. I've fixed hot docks, hot boats, and boats with galvanic corrosion problems, enough of them to make this claim: You bring your corrosion/electrolysis problem to me and I will fix it, promptly, effectively, for fair value, the first time around, or my work is free. No BS, if anyone wants to take me up on that, I'm right on the AICW at mile marker NC-198.

Cheers,
Nate

**Alan Wheeler** · 08-07-2007, 22:59

Quote:

Congratulations, Alan, on being the top poster on the site, you represent 5.6% of the view of this entire site, a ratio of 385-to-1. Please recognize one thing at least: A post such as my first reply in this thread is not just dashed-off in five minutes, it takes a lot of valued time.

OK, so please take very careful note of two points. One is the title under my name. "Site Administrator". This doesn't mean a heck of a lot, I am no more special than any other poster here. But it does mean that I have a great deal of work behind the scenes. Which equates to a lot of "posting" behind the scenes of this site and that contributes to the numbers that clock up beside my name.
Second point is to look at the number of years I have been here. If you align that with the number of posts made, you will see the ratio is much more realistic. But it seems that once again you have chosen to skew facts to make things sound different than they are.
I am sorry that I have taken up your much valued time and I am sure that all of us greatly appreciate you stopping by and giving us some of that valued time free of charge like that. From what you have stated I must have all the time in the world and obviousely as I do not have your expertese, my time is not worth as much. I do apolagise for wasting yours.