New Battery Bank to be rewired

[HueyHuey]

I am in the process of establishing a new house bank on my live aboard catamaran.
Cureentry all charging sources are directly connected to the batteries which are connected in parallel. The solar is through a regulator, the alternators first go through a bridging switch from the starter batteries. The wind generator is internally regulated and has an on/off switch. And the ABC charger is connected directly to the batteries.
I will now be connecting a Victron Battrry monitor BMW 700, the neg battery terminal to a shunt then the shunt to an Isolation switch and this to the alternator, main switch panel etc.
On previous boats I wired up the connections so that all charging connections were connected to an isolation switch first then to the battery, that way I could isolate the battery but still have a connection to power for my electronics etc, and it gave me a tidy way of controlling the wires.
The question is should I change the wiring on this new boat so that all charging and loads runs through the isolation switch whether positive or negative? That way no extra wires will need to be connect to the batteries themselves. OR should the positives still run to the battery and just have the negatives running through the shunt?
If any one could point me in the direction of some sample diagrams, that too would be appreciated.

[rwidman]

If I understand your post,, you are planning on installing an isolation switch in the negative battery lead. This is not standard practice and is a bad idea because when you turn this switch "off" all the circuits are still "hot". Nothing will work but all the wires and any connections, buss bars,, etc,, are still "hot" with respect to ground.

As for installing an isolation switch in the hot lead, this is how it is normally done. I would run everything through this switch except for bilge pumps and CO, smoke or propane alarms which should be powered on at all times. You still need overcurrent protection in these circuits though.

[rwidman]

If I understand your post,, you are planning on installing an isolation switch in the negative battery lead. This is not standard practice and is a bad idea because when you turn this switch "off" all the circuits are still "hot". Nothing will work but all the wires and any connections, buss bars,, etc,, are still "hot" with respect to ground.

As for installing an isolation switch in the hot lead, this is how it is normally done. I would run everything through this switch except for bilge pumps and CO, smoke or propane alarms which should be powered on at all times. You still need overcurrent protection in these circuits though.

[HueyHuey]

Sorry not very well worded. I have now installed the batteries. The negative go through a shunt for my battery monitor then to an isolation switch. The positive also runs through the isolation switch.

the question I guess is should all my charging be changed, the negative either off the isolation switch or shunt ( to keep tabs of usage and charge), and the positive off the isolation switch rather than directly off the battery as is currently the situation.

My logic is that if something happens to my house batteries I can quickly isolate them, but still use my starter batteries (through the emergency bridging switch) and they can still be charged because all my charging sources will be wired into my main isolation switch for the house batteries.

I will also be looking at installing a fuse in the positive rated at approx 150 amp.

Thanks

[rwidman]

Originally Posted by HueyHuey

Sorry not very well worded. I have now installed the batteries. The negative go through a shunt for my battery monitor then to an isolation switch. The positive also runs through the isolation switch.

the question I guess is should all my charging be changed, the negative either off the isolation switch or shunt ( to keep tabs of usage and charge), and the positive off the isolation switch rather than directly off the battery as is currently the situation.

My logic is that if something happens to my house batteries I can quickly isolate them, but still use my starter batteries (through the emergency bridging switch) and they can still be charged because all my charging sources will be wired into my main isolation switch for the house batteries.

I will also be looking at installing a fuse in the positive rated at approx 150 amp.

Thanks

The shunt is fine if that's what the instructions state. You should remove the switch in the negative conductor. Wire the negative terminal through the shunt and then directly to ground. No switch.

A 150 amp fuse will probably blow as soon as you try to start the engine.

Rather than trying to figure all this out from scratch, why not buy a good book on boat wiring and follow the diagrams?

[glenn.225]

Here's a couple of good links with lots of info

1-BOTH-2-OFF Switches Thoughts & Musings - SailboatOwners.com

Electrical Systems 101

And there nothing wrong with with a isolation switch on negative conductor as long as there is also one on the positive. It's not usually needed but nothing wrong with it.

[rwidman]

Originally Posted by glenn.225

Here's a couple of good links with lots of info

1-BOTH-2-OFF Switches Thoughts & Musings - SailboatOwners.com

Electrical Systems 101

And there nothing wrong with with a isolation switch on negative conductor as long as there is also one on the positive. It's not usually needed but nothing wrong with it.

Well there's nothing wrong with two or three switches either except it complicates things and provides additional points of failure. Normal electrical practice is to switch the positive lead only. Read my post above for why it is not a good idea to switch the negative conductor.

[btrayfors]

Here you go. No need to switch anything. Totally automatic charging of all batteries.

Just connect ALL charging sources -- battery charger, solar panels, alternator, generator, etc. -- directly to the HOUSE batteries, with appropriate fusing.

Bill

[smac999]

do not run your charging stuff to the output of the switch. because 1. when they switch is off your batteries don't charge. which is wrong. and 2. when you switch it off. the charging stuff will directly power your boat loads. which is bad.


go straight to house bank, though shunt


in north America we do not put switches in neg lines. seems common in Europe. I always take them out of beneteaus over here.

[rwidman]

It's pretty common for battery chargers to come with the capability of separately charging two or more battery banks. Wires are run from the charger to the common negative and directly to each battery.

It is important to have overcurrent protection at both the battery and the charger end of each positive wire because the conductor is fed from both ends.