New Inverter/House Bank

[Viper]

Qr Bbpost

Qr Bbpost If the shunt is in the circuit that requires two pos and two neg cables to carry the max load, then it must be wired that way through the shunt as well.

The victron shunts that I have installed are always in the black ground cable between the battery bank and the engine block / ground point......I don't understand why you would need two cables on each end of the shunt itself as it is only in the ground cable.

Depends on what you're monitoring. If it is to be IN the inverter DC load circuit, then you can't be required to use 4/0 cable for the circuit for example, but go with say 2 AWG cable through the shunt that is monitoring that particular circuit, that section of the circuit would have insufficient wire size to handle full load. That's why the shunt must be rated for the load as well, it's part of the circuit. If an engine block negative is part of the circuit's return path, then the cable to the engine and back to the source must also be 4/0 in this example. Unless I'm missing something, I don't know how you can get around that unless something other than the inverter DC load is being monitored here. I see it all the time though, the most common is heavy cable to the battery bank speced for a high load but forgetting to replace the smaller cables connecting the batteries together in that bank, they will all be expected to carry the same load.

If the shunts you've installed are simply to monitor the ship's banks, then that's different and the current cable size to the block in your cases is probably fine but unless I'm mistaken the OP in this case is monitoring his inverter load through it, maybe he can clarify this point.

BTW, if you're using an engine block for a high load/amperage connection point, never connect to one side of the block then take the return off the other side of the block. Both connections should be at the same terminal.

[vineyardgray]

Qr Bbpost I bet that crimper made things a lot easier, I use a hydraulic one.

Yessir it did!

Qr Bbpost
I trust that you'll secure all the wiring to the bulkhead after you're finished connecting everything?

Yep, ty wraps on everything.

[vineyardgray]

In my mind there are two circuits - one is the inverter circuit (dual 1/0) and the other is the existing house loads (dual AWG 2).

I want the victron to monitor the state of the house bank (including all the gozintas and gozoutas) and since both of those loads are now connected to the Firefly bank I assumed that in order for the monitoring to work right I needed both the house load negatives and the inverter negatives to return through the shunt.

There is a bit of a kludge going on at the moment because the house load negative is only connected with one AWG 2 through the port engine ground - this connects to the genny then to the stbd engine, then to the start battery bank, where it picks up the second AWG 2 and off they go to the panel (and presumably the boat through-hull ground, but I don't know where that connection occurs).

This brings up another question - there are two shunts on these number 2 already to drive the ammeters that measure amps on either side of the dc panel. Will these shunts cause a problem?

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[vineyardgray]

Another question - I had assumed that two of the wires on the common stud of the switch I removed were the alternator feeds - but once in the engine bay these appear to lead to the starter, which also makes sense. But then how did the alternator juice get to the batteries? Looking at the engine it is hard to see exactly what is going on but it appears the alternator and starter share that cable is that correct?

[Viper]

Depends on the application but typically the alternator output is hooked up at the starter unless an isolator has been installed.

[bud37]

Qr Bbpost I want the victron to monitor the state of the house bank (including all the gozintas and gozintas) and now that both of those loads are connected to the Firefly bank I assumed that in order for the monitoring to work right I needed both the house load negatives and the inverter negatives to return through the shunt.

Could it be possible to have a ground bus bar ( that is connected to boat ground ) that all 12v grounds run to in your installation ? That way it is neat and the connections will be all ok.

Consider, then from the battery bank in question to the shunt, then from the shunt to the bus with only one properly sized cable. This is what I was hinting at before. I still like that panel...

[vineyardgray]

Qr Bbpost Depends on the application but typically the alternator output is hooked up at the starter unless an isolator has been installed.

So the starter draws current from the batteries to start the engine and then the alternator uses that same wire to pump current into the batteries? Makes sense. So I'm immobile at the moment is what you're telling me.

Now I need to figure out how to have the starter draw from a different set of batteries (the start bank) and have the alternator feed the house bank.

I've got quite a bit of 1/0 left over - is it as easy as adding separate alternator and starter cables?

[vineyardgray]

Qr Bbpost
Could it be possible to have a ground bus bar ( that is connected to boat ground ) that all 12v grounds run to in your installation ? That way it is neat and the connections will be all ok

Yes, that is the way I intend it - it is just that Carver buried the majority of the cabling (both AC and DC) where it is difficult or impossible to access. Will work towards that goal.

Qr Bbpost
Consider, then from the battery bank in question to the shunt, then from the shunt to the bus with only one properly sized cable. This is what I was hinting at before.

Yes - the challenge I think is the bus bar required to handle the fused value (400a). I might need a whumper of a cable also. Although I suspect this design of mine has used heavier gauge wire than required.

[Viper]

Qr Bbpost.....Now I need to figure out how to have the starter draw from a different set of batteries (the start bank) and have the alternator feed the house bank.....

It's done all the time. This is what I was referring to earlier. The starter gets hooked up to a start bank and the alternator output is disconnected from the starter and directed to a multi-bank battery isolator or ACR. From there, the output is directed to multiple banks while keeping them all isolated from one another. There are several devices available that will handle either a single alternator input or two alternator inputs. The advantage of using two alternators on the same isolator for example is that if one alternator fails, all the banks will still be charged by the alternator that is still working, which adds a margin of redundancy and safety. Many ways to accomplish the same thing here.

[vineyardgray]

It might be done all the time but not by me

Eventually I will upgrade the alternators to higher amp models (Balmar, etc) with external regulation (Wake Systems, etc).

What do I do short term to start the boat? Assume connect both alt/start hot to the starter battery bank? I have to get this boat to the haul out pretty soon. There's nothing like panic to boost productivity lol