Final wiring diagram before install, fusing & cable sizes, have I missed anything?

steve yates said:
I’m guessing you meant why not do it the best practice way?
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Yes.
steve yates said:
I absolutely agree, I would and I hope I will. If I can understand what that is!
Something it appears I am obviously struggling to understand.

For instance when you talk about negative busbar, do you mean the shunt


I do have a negative busbar in the distribution box to take the house battery negative and for all the domestic loads, like vhf, lights etc. but I cannot imagine you mean it should also be taking cables from the engine battery and the engine? For a start there is no room.

Its the introduction of an engine that throws me I think. In my wee boat the 12v system was simple, none of this common ground stuff, and no engine involved at all.

If someone could tell me, from my wiring diagram above, which two points to draw a black line between to make sure my dc to dc charger works and if any of the black lines in it are wrong, then that would tell me so much more than any explanation involving the words common ground. And probably make sense of what you are all trying to tell me.
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Your digram is wrong with regards to the negatives. You have the distribution panel negative coming from the battery side of the shunt, that won't work.

The negatives from each battery go to their respective BMSs. The BMS P- from each BMS goes to the battery side of the shunt, nothing else can be connected here.

You connect a busbar to the load side of the shunt. You connect to the shunt, engine battery, engine negative, charger negatives, DC-DC charger negative, negative to the distribution panel etc. It is this busbar that is the common negative/ground, everything connects here.

In your diagram you show negative in and negative out for the DC-DC charger, that isn't the case, the DC-DC charger only has a single negative connection, as above, this goes to the busbar.
 
PaulRainbow said:
Yes.

Your digram is wrong with regards to the negatives. You have the distribution panel negative coming from the battery side of the shunt, that won't work.

The negatives from each battery go to their respective BMSs. The BMS P- from each BMS goes to the battery side of the shunt, nothing else can be connected here.

You connect a busbar to the load side of the shunt. You connect to the shunt, engine battery, engine negative, charger negatives, DC-DC charger negative, negative to the distribution panel etc. It is this busbar that is the common negative/ground, everything connects here.

In your diagram you show negative in and negative out for the DC-DC charger, that isn't the case, the DC-DC charger only has a single negative connection, as above, this goes to the busbar.
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No, I only have the batteries to the battery side of the shunt, its my wierd diagramming thats makes you think otherwise. I split the shunt vertically, via the labbelled dotted blue lines, load side is lhs and battery side is rhs of shunt, after drawing the lines I obviously could have kept it conventional and used top end for load and bottom for battery.

2nd para, Got that, presumably with the class t fuse between bms and shunt?

3rd para. Ok, I see what you are saying, this was confusing me as it didnt exist in my diagram.
So you recommend I add that busbar rather than just connecting it all to the shunt loadside?
Just to clarify, does the engine battery negative terminal still have a cable direct to the engine ground?
Or is this connection to the busbar instead of that?

Para 4. Understood, I haven’t looked at it yet, I had just searched for wiring a victron dc to dc when drawing up the diagram.

Thanks.
 
steve yates said:
No, I only have the batteries to the battery side of the shunt, its my wierd diagramming thats makes you think otherwise. I split the shunt vertically, via the labbelled dotted blue lines, load side is lhs and battery side is rhs of shunt, after drawing the lines I obviously could have kept it conventional and used top end for load and bottom for battery.

2nd para, Got that, presumably with the class t fuse between bms and shunt?
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No, the fuse is between the battery positive and the isolator.
steve yates said:
3rd para. Ok, I see what you are saying, this was confusing me as it didnt exist in my diagram.
So you recommend I add that busbar rather than just connecting it all to the shunt loadside?
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Yes.
steve yates said:
Just to clarify, does the engine battery negative terminal still have a cable direct to the engine ground?
Or is this connection to the busbar instead of that?
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Engine battery and engine negative both go the the busbar, no need for anything else.
steve yates said:
Para 4. Understood, I haven’t looked at it yet, I had just searched for wiring a victron dc to dc when drawing up the diagram.

Thanks.
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Some DC-DC chargers had two negatives (as in your diagram), those are for installations where the engine and domestics are isolated.
 
steve yates said:
Thanks paul, and yes of course, the fuse is on the pos side, Immediately after the bms.
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No it isn't, the BMS terminal connections are all negative, the only positive is the thin wire that is already connected to the multi-plug. If you make a positive connection to the BMS it will destroy it.

The positive on the battery goes to the fuse, then from the fuse to the isolator.
 
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