Need Help - BMV-600 Monitor Installation

[night0wl]

Hey Everyone!

I recently purchased a BMV-600 single bank monitor for my Beneteau 343 sailboat. Upon getting started with my installation, I noticed that my boats wiring is a bit different that what could be expected in the installation manual provided by Victron.

First, some background. My boat has 2 battery banks, however I am only concerned with monitoring my house bank. The 2 banks are all populated with Group 27 flooded batteries. The starting bank is a single Group 27 battery. The house bank, however, has 2 Group 27's wired in parallel.

The positive posts of each battery bank is wired to its own separate positive switch....meaning, if I wanted to shut off/isolate the starting bank, I would simply turn off the positive switch for that bank. However, for the negative side of things, both banks are wired to a common negative switch. Meaning, if I wanted to shut off the entire electrical system to the boat, I would simply throw the switch for the negative bank. All this is standard I'd imagine for many boats.

Here's where I'm a bit confused. On the negative switch, all of my battery cables seem to be crimped together onto a single lug which is then then attached to the negative switch. I'd imagine Beneteau did this to save some bucks of having to crimp seperate connectors for everything that needs to attach to the the negative switch and keep things cleaner. See this picture for the visual (sorry for quality...cameraphone):




As I would like to install and monitor only the house bank, I am wondering if I can simply take that common, crimped cable and attach it to one end of the shunt of the monitor. Then have another battery cable fabricated and take it from the other side of the shunt and attach it to the common negative switch. OR, since I only want to monitor the house, would I be required to uncrimp the cables and separate the house bank negative cable and ONLY attach the house bank negative cable to the shunt and place all the rest directly on the negative switch?

I want to desperately to get this project done this weekend and cant wait for Victron support to be back online on Monday. Please help!

[btrayfors]

See my reply on CruisersForum: BMV-600 Installation Question - Cruisers & Sailing Forums

[night0wl]

Ok - thanks for the advice group. I will definitely invest in a negative bus bar and then clean up all the wiring. In the interim, however, here is what I did.

1) Bought two feet of 2/0 black battery wire
2) Bought three battery crimps 2/0 size
3) Bought heatshrink]
4) Bought some 5200
5) Bought box of stainless steel wood screws
6) Bought 2 stainless large wood screws

I cut the existing cable for the house bank behind the crimp and taped off the remaining stub of the old cable with heatshrink and electrical tape. I then crimped on one of the battery connetors onto the old battery cable and applied the heatshrink. I think fabricated my battery cable out of the 2 ft 2/0 gauge wire and remaining crimps and heat shrink.

I then mounted the shunt onto a block of mdf using the large wood screws (fender washers wouldn't fit...need to find smaller ones) and then used 5200 to mount that block to the wood in the battery locker, then connected everything up per instructions. The old house negative cable with new crimp to the one side of the shunt and the new fabricated cable from the shunt to the common negative. As it stands, the rj cable is still going across my sole...need a second pair of hands to help fish it through the cable chases, but I have my handy-dandy fish tape ready to go!

I then dry fit everything up, and it looks like I'm in business!






Two more projects have come from this project. First, I need to install that negative bus bar and clean up all the cables that are on the shared common negative. What a mess. Beneteau has done a spectacular job with the wiring elsewhere, but this just is worthy of a beat down.

Second, I have a voltage leak somewhere (as I long suspected). With everything turned off, I still track -0.25 to -0.5 amps somewhere. That seems to be a lot of stray voltage...no?

Lessons learned...a 2 hour project will inevitable take 7. Also, make sure you have a vacuum handy when you use a hole saw to drill through the wood...I forgot to have something catch the savings/sawdust...what a mess Lastly...if you want to do something right, it takes tiiiiiime.

I wanted to install the bilge counter today too..but *sigh* I guess it will wait for another day.

[MJBrown]

The shunt simply goes in series on the negative side of the house bank so what you did appears to be fine. Before you get too involved chasing down a stray voltage problem use an amp meter to see if you really have current flow. Or if you don't have an amp meter take a reading at the house batteries then at the DC panel. With everything off it there should be minimal differences between the two readings. It could be all you have to do is "zero" out the BMV unit so it recognizes what true zero is on your boat. I'd also be carefull about inserting a Negative Bussbar in place of the existing setup. More connections can equate to more problems later on. Such as voltage drops from poor connections, corrosion, etc.

[Deadhead]

The BVM will draw 4 milliamps on its own so you will never see a zero current draw.

[galynd]

I have the same unit. Mine reads 0.00 when all switches are off except bilge pump.

[night0wl]

Originally Posted by MJBrown

The shunt simply goes in series on the negative side of the house bank so what you did appears to be fine. Before you get too involved chasing down a stray voltage problem use an amp meter to see if you really have current flow. Or if you don't have an amp meter take a reading at the house batteries then at the DC panel. With everything off it there should be minimal differences between the two readings. It could be all you have to do is "zero" out the BMV unit so it recognizes what true zero is on your boat. I'd also be carefull about inserting a Negative Bussbar in place of the existing setup. More connections can equate to more problems later on. Such as voltage drops from poor connections, corrosion, etc.

Can you educate me on how to the amp settings on my multimeter? I have amp settings but have not used them in a long time. Last time I tried, I did something wrong and sent out an electricity arc. Ever since then, I've been wary of ruining anything. I use the voltage setting all the time...the meter and the batteries all check out (13.3 volts...seems fully charged).

Pic of my multimeter below:

[brak]

the problem with using a basic meter to measure current is that you have to connect it in series. In this case, to verify the overall current/leak you'll have to put it somewhere inline with one of main battery wires - negative or positive.

if you know exactly what size shunt you just installed, you can instead measure voltage across this shunt and convert that to amps.

Most standard shunts are either 50mv or, somewhat more rarely, 75mv rated for their given amps. I.e., let's say your shunt is 100 amp, 50mv. That means that if you put a *voltmeter* across your shunt, it will read 50mv (milli volt) when current is 100 amp. For smaller values, amps are proportionately lower, i.e.:

Current Amps = Measured mv * 100amp / 50 mv

This way you don't have to take anything apart and run a much smaller risk of sparks flying.

I would bet though, that since your monitor shows current flowing, that's probably what the value would be when you use a multimeter (that monitor is an ammeter too). Assuming that's the case, you pretty much have to measure every circuit separately, until you find where the leak is. I would start by trying all circuits at the main switch panel.

To avoid having to disconnect things, you can begin by measuring voltage between the positive side of circuit *after* the breaker and somewhere on the negative side with breaker OFF. If circuit is properly off, there will be no voltage. If circuit is somehow energized, there will be voltage. If you don't find anything that way - time to start really digging

0.25amp is nothing to sneeze at, it will drain your batteries in a few days and equals a single LED light fixture or so.

[Maine Sail]

Originally Posted by Deadhead

The BVM will draw 4 milliamps on its own so you will never see a zero current draw.

4 milliamps is .004 the BMV-600 series only reads to .01..

Never see zero....

[Bene505]

Originally Posted by night0wl

Can you educate me on how to the amp settings on my multimeter? I have amp settings but have not used them in a long time. Last time I tried, I did something wrong and sent out an electricity arc...

When a miltimeter is set to measure amps, it is very susceptible to frying the internal fuse. If you accidentally connect it to power and ground, like you are measuring voltage, then you may see a spark, but you'll certainly fry the fuse and maybe damage the amp setting on the meter.

Check to see if your amp meter setting is still working by putting it in series with a low current light or something within you meter's measuring range. if it doesn't work, replace the internal fuse.

Good luck tracking down the leak. I found my sterio (Clarion, marine unit, CMD4 maybe?) had a little box that helped keep the memory presets when the power is off. The leak went through a separate wire connected to the battery's positive terminal. It was malfinctioning and draining an incredible amount of amps, 24 hours a day - even with the main house switch off.

So from my experience, check the "extra" wires on your + terminal first. The switches in you panel are probably not leaking current, it's probably something that was added. If the "extra" wires are ok, then check your main red (+) wire at the terminal. Go downstream from whatever you find is leaking. (Actually, it's upstream since electrons flow from minus to plus.)

Regards,
Brad