Galvanic Isolator in a Steel boat

[milfordman]

My 20 year old steel ebbtide 33 has untill this year had a basic 12 volt system. The boat has two bronze sea cocks, one well forward on starboard side :- toilet outlet. The second sea cock :- sea water inlet on port side towards stern. The bronze 3 fixed bladed prop is on a Stainless Steel shaft ( 316). There are two 250mm zinc anodes one each side of the keel towards the stern, and a small zinc annode on the propshaft. I have checked my prop and sea cocks regularly and so far they have been OK, they are the originals. I have changed the prop annode approx every 2 years, and the main annodes every 4 years. So I have considered the setup to be satisfactory. The boat has so far allways been on a swinging mooring in the summer and in the boat yard during the winter, when I would have used 240 Volts for batery charging, and power tools with RCD in extention. However I Have now installed A 240 volt RCCB circuit breaker in the boat with A Stirling 20 Amp smart charger, and a Sterling Galvanic Isolator, all wired as recomended by Stirling. I fitted all this equipment early this summer and had it working in the boat yard. Now my boat is in tha Marina I was going to hook it up to the shore supply the next time I go down. The problem is I just read on the experts advice page that fitting a galvanic Isolator on a steel or aluminium boat is more complicated. Could some one advise is my setup ok, or should I do more?
A separate question I also fitted a Stirling Advanced regulator to my Lucas 70 amp Alternator, and the remote panel. When the alternator runs I can get currents as high as 140amps. the regulator seems to be doing as it is suposed, i.e. no output then ramps up to high level then ramps down when charged. The setup reads temperature of alternator and battery and regulator all rise but stay within acceptable limits. Good job I fitted the 40 mm area cables as recommened. I just don't understand how you can get 140amps out of a 70 amp Alternator?

 

[pvb]

140amps...

What system are you using to measure the charging current?

 

[milfordman]

Re: 140amps...

The advanced regulator comes with 2 shunts which are wired into the main circuits with bell wire used to feed the volt drop across the shunts to the regulator and the remote display is plugged into the regulator.

 

[William_H]

Re: 140amps...

The 140 amps you read is almost certainly an inaccuracy in the current measurement. The error can only be in the resistance of the shunt.
The shunt is a very low value resistance which developes a voltage drop across the resistor when the current flows. This voltage is measured.

Now the resistance is so low that any slightly poor bolted terminal connection can produce similar amounts of resistance.
What you need to do when designing a shunt is to have eg a piece of resistive metal in a bar shape. You put holes in each end to bolt on the cable that carries the current. The small wires which sense the voltage drop need to be connected seperately to the resitsive bar so you meanure only voltage drop across the resistive bar.
If you connect your 2 sensing wires to the same lugs as the current carrying wire then any resistance in the connection to the bar develops a voltage drop which is added to the required volt drop which you measure. Hence over current reading.

Now I feel sure that Advance would be aware of this trick and that you have wired it in correctly but I explain just to make sure.

The other possible source of error is if you have wired the 2 shunts in series such that the voltage drop you are measuring is across 2 shunts at once. 2 shunts will double the resistance hence double the voltage drop hence double the amps indicated. If you are not sure perhaps you could temporarily remove one shunt but of course connect the main wires together to bypass the shunt.

Sorry can't help much more without more detail. But you should check all the installation design again.
Regarding Galvanic isolator I can't imagine any different problems in a steel boat.
good luck olewill

 

[pvb]

Re: 140amps...

[ QUOTE ]
The advanced regulator comes with 2 shunts which are wired into the main circuits with bell wire used to feed the volt drop across the shunts to the regulator and the remote display is plugged into the regulator.

[/ QUOTE ]I didn't realise the Sterling Advanced Regulator's remote display could show charging current (and it's not mentioned on the Sterling website). Is this a new feature?

 

[VicS]

[ QUOTE ]
fitting a galvanic Isolator on a steel or aluminium boat is more complicated.

[/ QUOTE ] Like Willam H i cant think what can make it more complicated. Its only got two connections and those are interchangeable. You may have to pay more attention to the vessels earthing system though, but that would apply regardless of the GI.
Take a look at the Instructions for fitting the GI on Yandina.com and also an expanation of how it works.

Yandina is a steel yacht

 

[milfordman]

Thanks for the info. You are right the voltage sensing wires are connected to the side of the bar and the main current carring cables are bolted via large bolts on the end. I don't think I can have the two shunt wired in series as one shunt senses the alternater current, and the second shunt senses
the current going to the domestic bank of batteries. As I said I think the regulator is working ok, because although I am getting this very high charging current. The other data seems to be ok. The sequence of events, is as follows. When the engine starts, the output is initially only 5-10 amps and only goes to the starter battery, the logic being it is most important to recharge the starter battery following starting the engine. After approx 5 minutes the charging rate gradually increases over a period of approx 30 seconds up to the full charging rate, this is to avoid belt slippage, the majority of the current goes to the domestic batteries. The remote display unit has two lines of text, and the default info displayed is alternator voltage and current, and domestic battery voltage and current. The difference between the current readings would be going to the starter battery. It is also possible to select to display starter battery voltage and current. A third option is to display alternator body temp and domestic battery temp, it is also possible to display the temp of both sides of the regulator unit. Thinking back to when I installed the equipment, one aspect that I had great trouble with was connecting the voltage sensing wires to the regulator. The connection was via connectors which are spring loaded closed and opened with a tiny plastic lever. I had to try repeatedly to get the wires to enter the connector however I eventually succeeded, I thought that the connection was ok as the wires would not come out when given a gentle tug, I am also quite sure the insulation was stripped back correctly. All the same you have set me thinking. Thanks Ref:- Galvanic Isolator, I was quite happy with the setup untill I saw the info given on the experts page.

 

[milfordman]

Thanks Vic S I have looked at the Yandina Site the explanation was very useful, because I did not know how it worked. The fact that it blockes the 1.5 volts that would be the galvanic current, but allows the higher voltage that would be present in a short situation is of course blindingly obvious now that it has been explained. Like so many things in life it is easy when you know how. Once again thanks for the info much apprieciated

 

[VicS]

[ QUOTE ]
Ref:- Galvanic Isolator, I was quite happy with the setup untill I saw the info given on the experts page

[/ QUOTE ] What experts page is that?
I thought THIS was THE experts page!

 

[William_H]

Just to be more specific the shunts are actually in series going first through the alternator current shunt then through the domestic battery current shunt. That is fine provided you pick off the voltage from the 2 shunts individually. But if you got the wires from the shunt to the readout swapped over you could have a wire from the input of the alternator shunt and the wire from the domestic battery shunt load end which would give you the cumulative out put of both shunts (double current readout) of course this would the other 2 wires would not give any readout. So perhaps not likely. But something must be wrong. Perhaps even wrong shunts. olewill

 

[milfordman]

Thanks William_H I will check them out as soon as I go to boat again, also will ask Stirling If it is possible they have supplied wrong shunt