Electrolysis caused by a non-isolated alternator

Bill & Judy Rouse <yahoogroups@...>


I know you have checked this out, but your large alternator should also be isolated. If the new engine mechanic used the same alternator that Amel installed, you are probably OK, but I remember you saying Balmar. Although I think Amel uses Balmar now, BeBe, 387, was fitted with a Leece-Neville 175 amp 24V alternator.

If you recall, when all of this started, I suggested that you should check your alternators to ensure that they were isolated. I suggested this because I had a friend who owns a Bavaria and who lost his sail drive because he added a high output Balmar Alternator...and failed to order one with and isolated ground.

I am happy that you are making great progress. I also appreciate all of the information shared by you and all the others...I think that I am better informed.


Bill Rouse
BeBe Amel 53 #387
sent from my tablet

On Feb 4, 2015 2:08 PM, "Kent Robertson karkauai@... [amelyachtowners]" <amelyachtowners@...> wrote:


Thanks Olivier,
I guess the original owner had double pole breakers installed.  I should be able to isolate the engine from the batteries when not running it.
There is nothing on the battery side of the switch except the battery cables.
Thanks again.

On Feb 4, 2015, at 2:55 AM, Beaute Olivier atlanticyachtsurvey@... [amelyachtowners] <amelyachtowners@...> wrote:


Hi Kent,

with the batteries breakers you have now, you can't turn the engine OFF only while running (or being in the harbor or at Anchor). One of these breakers cuts both 12 and 24 positives, the other one cuts both negs.
You'll have to install a new double circuit breaker, cutting +12 and -12V.

I'm glad you finally seem to find the cause of the corrosion.

Have a good day.


On Wednesday, February 4, 2015 4:52 AM, "Kent Robertson karkauai@... [amelyachtowners]" <amelyachtowners@...> wrote:

Thanks Olivier,
I've got a plan now.

The voltage thru the bonding system is battery voltage (25-27VDC), but it won't light a 5watt bulb.  Mike (electrical engineer) doesn't think it's what caused the electrolysis of the prop shaft.
I found several other issues created by the guy who put the new Yanmar in (it's a non-isolated engine, and I don't think it was bonded to the rudder zincs).  The guy who put the new chargers in connected them to the bonding system that was attached to the Yanmar, and one of them failed.  That combination of errors is what we think caused the damage.

I'm waiting to hear back from Yanmar to see if there's anything I can do to isolate it from the 12V system. If not I'll have to be very particular about leaving the battery switch off when not running, and will definitely change the alternator to an isolated one.

I sure have learned a lot about electricity and about Amel's systems.  Thanks again to everyone for your guidance and continued help as I've muddled along.

I'll let you know what I find when I'm finished searching for the bonding voltage.
Steady as she goes.

On Feb 3, 2015, at 12:57 PM, Beaute Olivier atlanticyachtsurvey@... [amelyachtowners] <amelyachtowners@...> wrote:

Dear Kent,

you don't need to pull the neg wires out of their ducts, but only disconnect the neg wire where it is attached to the item (motor, relay, pump, nav light, fridge, etc...). One week should be enough....


On Tuesday, February 3, 2015 3:45 AM, "Kent Robertson karkauai@... [amelyachtowners]" <amelyachtowners@...> wrote:

Thanks Eric.  That makes sense. So everything on the winches breaker on the 24V panel goes to the control panel at the helm and the breakers throughout the boat go to the motors and pumps directly. So I need to go to each winch and pump separately, disconnect the neg wire and see if the voltage between the pos battery pole and the bonding disappears.  I think.  I'm still wondering if the bond/neg connection is somewhere between a motor and the battery, how am I going to find it?  I guess that means tracing every neg wire back to the battery.  Ugh, most of them are in chases where they aren't visible. That'd mean pulling them out, checking them, and running them back through the chase.  That might take me a month or two.😩

On Feb 2, 2015, at 9:19 PM, kimberlite@... [amelyachtowners] <amelyachtowners@...> wrote:

The breaker on te 24 volt panel does not control the winches and a number of other things. That breaker only controls the control relays. The actual hi load breakers are as note in my previous note,

----- Original Message -----
From: "Kent Robertson karkauai@... [amelyachtowners]"
Date: Monday, February 2, 2015 6:21 pm
Subject: Re: [Amel Yacht Owners] Re: Prop Shaft Electrolysis
To: "amelyachtowners@..."

> Aha! Thanks Bill. What does that "Permanent" stepdown 
> transformer feed?
> The + wire to the permanent stepdown transformer is the only one
> I see that is attached to the main service battery switch on the
> positive battery side of the switch. I was surprised that the
> bilge pump wasn't connected there too. I'd never checked
> before, but the bilge pump doesn't work when the battery switch
> is off. So I guess the permanent transformer is the only thing
> that is powered when the battery switch is off?
> Is there a place that tells what these other equipments are that
> don't go through the 24v panel? I know where most of the
> breakers are that go to the winches, heads, anchor wash,
> windlass, thruster, furlers, etc. They are all dependent on a
> breaker on the 24V panel. I don't know where the breaker is for
> the aft lazarette receptacle for the dinghy inflator???
> I've found 24 V between the bonding system and the Positive
> battery pole. I think that means there is a connection
> somewhere between a negative wire and the bonding system. It
> carries 0.8amps with all 24v panel breakers off. My next
> project is to disconnect all the negative wires at their
> equipment. If the connection between the battery negative and
> bonding is not at the pump or motor, but somewhere between
> battery and the equipment, I don't think I'll find it by
> disconnecting neg from equipment. Then what???
> Thanks to all!
> Kent
> SM243
> Kristy
> On Feb 2, 2015, at 4:45 PM, 'Bill & Judy Rouse'
> yahoogroups@... [amelyachtowners]
> wrote:
> Kent,
> There are many loads that do not go through the 24 volt breaker
> panel and the "Permanent" 24 to 12 volt step-down transformers
> are one example. The breaker for these is inside the wet
> locker...additionally, and I am fairly sure, that this breaker
> remains HOT with the battery switches turned OFF.
> Bill
> BeBe 387
> > On Mon, Feb 2, 2015 at 1:30 PM, karkauai@...
> [amelyachtowners] wrote:
> >
> > Hi again, all,
> > another question:
> > Are there any permanent loads on the 24V system that don't go
> through the 24V panel.
> >
> > On some schematics I found something called "permanent" on the
> 24V system that doesn't appear to be on the 24V panel and
> doesn't have a breaker on it in the schematic.
> >
> > Thanks,
> > Kent
> > SM243
> > Kristy
> >

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