Battery Monitor Configuration

[Dockhead]

When I installed my Victron battery monitor, my boat's service batts were still divided into two banks. Now they are combined into one big bank. So the battery monitor gives weird info - the shunt is only on the ground wire of half of the batteries.

Now that I have new batts I am thinking again about how best to monitor them. The obvious thing to do would be to combine the two ground wires at the shunt so that the Victron works as it should. But this will add 20 feet of cable to the wiring of one part of the bank - seems like that would exacerbate any imbalance. Since I don't worship the "percentage capacity left" reading on the meter, paying rather more attention to voltage trends and total amp/hours used, it's also conceivable to just leave it like it is, double the amp/hours used reading, and rock and roll(as I've done for the last two years. However, there are a couple of other ways to do it:

1. Install a second Victron meter (they're not that expensive) with a second shunt at the second ground wire. Aggregate the amp/hours used readings of both meters.

2. Add a "Smart Gauge" meter which does not measure amp hours in and out; rather it does a sophisticated analysis of the voltage trends.

3. Add both a second Victron and a Smart Gauge.

What do you guys think?

[sailorboy1]

I would combine the banks into one as far as the monitor goes (that is how I have mine even though there are 2 banks they both on-line normally and that is how I have the monitor setup). Isn't there a way to install the shunt at a location that could allow the cables to be about the same length?

I think as far as the monitor goes the longer cable issue probably only matters during high demand use like a mircowave. And then the error as far as operating your electrical is is minor.

[mbianka]

Why not just move the shunt halfway between the two banks grounds? Not sure why you would have an extra twenty feet of wire since both banks battery grounds should really end up at the same point on the boat.

[Dockhead]

Originally Posted by mbianka

Why not just move the shunt halfway between the two banks grounds? Not sure why you would have an extra twenty feet of wire since both banks battery grounds should really end up at the same point on the boat.

You're right; I hadn't realized it, but there is a master negative bus bar where the negatives of both banks end up. The shunt should go there. Now the problem is that this is a highly engineered bit of the boat with no easy way for DIY configuration. I'll need to add a mini bus bar for the two battery bank negatives then put the shunt into the link between the new mini bus bar and the old large one. With currents up to 500 amps (I have a 10 horsepower bow thrusters) the engineering of this is critical. I will have to have it done professionally, I'm afraid, which means it will be more expensive than any of the things I was thinking about, even if it's simpler in theory But I guess I'll take advantage to put in a fusible link at the same time - something I've been thinking about anyway.

[mitiempo]

Originally Posted by Dockhead

You're right; I hadn't realized it, but there is a master negative bus bar where the negatives of both banks end up. The shunt should go there. Now the problem is that this is a highly engineered bit of the boat with no easy way for DIY configuration. I'll need to add a mini bus bar for the two battery bank negatives then put the shunt into the link between the new mini bus bar and the old large one. With currents up to 500 amps (I have a 10 horsepower bow thrusters) the engineering of this is critical. I will have to have it done professionally, I'm afraid, which means it will be more expensive than any of the things I was thinking about, even if it's simpler in theory But I guess I'll take advantage to put in a fusible link at the same time - something I've been thinking about anyway.

You don't have to use a mini bus bar - they are rated for differing currents. Use a powerpost as shown below - they are not rated for current as it depends on the lugs used on the wire. More compact as well. They are available with up to 3/8" posts. Blue Seas product.

There is no reason to fuse the negative cable but there should be a fuse in the positive cable.

[40 South]

Why not remove both negative cables from the buss bar and connect both to one end of the shunt. The other end of the shunt then goes back to the buss bar.

Craig