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sooty1957...
sooty1957...

Posted: Sun Apr 11, 2010 8:23pm

Post Subject: twin alternator diagram??

Hello , I have a 'sailaway; with twin alternators. One alternator is pre wired to the starter/engine battery with neg taken to engine block (usual sense wire and warning lamp wire).Positive taken to Starter feed. I assume the second alternator is wired individually back to the cabin battery (25mm red and black)but do you take a negative to the HULL? or even link the two battery negatives ? The 240v earth has been connected to the hull. Could you point me in the direction of a circuit diagram for a twin alternator arrangement? Thankyou Steve

Tony-B...
Tony-B...

Posted: Mon Apr 12, 2010 7:36am

Post Subject: twin alternator diagram??

There is a diagram here:- http://www.tb-training.co.uk/twinalt.html (all on one line and the hyphen is needed). A heavy negative lead is used to join both battery bank negatives and the negative going to the engine would normally be fitted with another short & heavy link from the engine block to the engine bed or other suitable hull bond point. There should be NO OTHER connections to the hull save for a 240CAC earth bond if any form of "mains" is fitted to the boat. The mains bond should be as close as possible to the DC bond point.

sooty1957...
sooty1957...

Posted: Mon Apr 12, 2010 7:45pm

Post Subject: twin alternator diagram??

A BIG thankyou, just the job. Steve

sooty1957...
sooty1957...

Posted: Mon Apr 12, 2010 7:55pm

Post Subject: twin alternator diagram??

Hello again! just noticed two things: 1. the alternators on your diagram are wired BEFORE the master switches, is this correct ? I noticed on my exsisting set up that it is after. 2. I think there is a wire missing on the diagram between the energising relay and the 'F' terminal? Thanks again Steve

Tony-B...
Tony-B...

Posted: Tue Apr 13, 2010 9:16am

Post Subject: twin alternator diagram??

Please read the whole of the basic alternator section in the notes I gave you an URL to. There are a number of different opinions on which side of the master switch the alternator main output is wired to. It is claimed the diodes in the alternator provide the BSS required isolation and it prevents the danger of damage it the master switch is turned off with the engine running. The notes are support a course and simply reading then does not give you the explanations you get on the course. There is no wire missing from the diagram on my computer, however the scaling your computer may be doing to get the digram on a smaller/low res screen might hide the thin lines. Tony Brooks

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