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diodes in marine twin engine installation

MM0TJR

Oct 2, 2012
15
Joined
Oct 2, 2012
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15
The attached diagram shows our Main Engine battery circuits.
We have 2 engines, port & starboard. each has its own battery.
each battery is "available" to either engine at the flick of the selector switch. This (we presume) is to allow starting of either engine from any battery in case one of the batteries goes flat.

What function do the diodes perform? & why.
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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They allow either engine to charge both batteries and prevent one battery from discharging into the other (for example, if there were a shorted cell in one)
 

MM0TJR

Oct 2, 2012
15
Joined
Oct 2, 2012
Messages
15
either engine to charge both batteries

pls could you clarify that -
with the wiring shown, any engine will only charge the battery selected. not both batteries.

also

prevent one battery from discharging into the other
the switches mean that the + terminals of the batteries will never be connected together.
supposing the diodes were replaced by conductor, then the - terminals would be connected together.but the + terminals will still never be connected therefore no current could flow between the batteries.

or am I being even denser than usual
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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You're right. If the diodes are connected like that it is done to prevent them from being charged.
 
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