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[E32-3] Installing Victron BMV-700

Geoff W.

Makes Up For It With Enthusiasm
Blogs Author
Hi folks,

I need some help. I purchased a Victron BMV-700 battery monitor to help me monitor amp draw (and see what's sucking so much dang power) and am trying to install it myself without going to a shop.

I've read the nice Marine How-To guide probably 10 times by now: https://marinehowto.com/installing-a-battery-monitor/ But their example setup is a nice, clean, wall-mounted demonstration:

05-Installing-A-Battery-Monitor.jpg

and what I'm looking at is much more of a mess:

IMG_20181007_123646.jpg
IMG_20181007_123624.jpg

So my understanding from their example is that I need to have the following:

1. ONE connection from the positive side of my batteries (do the batteries need to be connected via positive for this?) to the positive plug on the shunt.
2. The system ground attached to the "bottom" of the shunt
3. The "top" of the shunt connected to a bus that has the various negatives/grounds of the system attached.
3a. Obviously looking at the back of the AC panel, I won't be running every negative system line to the shunt/negative bus bar...is there kind of a collected, panel-wide negative ground somewhere on the back of the AC panel? If so can you point it out to me?

It's mad spaghetti back there and I am a little more intimidated than I felt going into it before I opened up the AC panel.
 

Geoff W.

Makes Up For It With Enthusiasm
Blogs Author
This is a dumb question, but with your batteries connected like that, can you still run them separately (1/2/All)? Mine look to be connected at the negatives but not positives.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Maine Sail is good on Victrons: https://marinehowto.com/installing-a-battery-monitor/

I think if you intend to install the Victron yourself, it will pay off to first do some basic upgrading to the DC panel. The factory panels did not anticipate current electrical needs.

This 2-part intro might be of interest: http://www.ericsonyachts.org/infoex...-1-A-Novice%92s-Guide-to-Panel-Reorganization

Success in installing a battery monitor means understanding the boat's wiring (which is usually haphazard), so that everything goes through the shunt.

I had an electrician sign off on both my Victron installs, just so I knew the readings would be as reliable as possible.

(Sorry not to notice Maine Sail's link was already read 10 times by Geoff...see first post. But he changed the name of his Web site and I ain't used to that yet..or many other things)
 
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Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
This is a dumb question, but with your batteries connected like that, can you still run them separately (1/2/All)? Mine look to be connected at the negatives but not positives.

If looking at the picture of our boat's house bank, that is one (1) bank. We do still have and use the factory 1-2-all master switch, but the second bank is a separate emergency 12 volt agm battery installed under the aft berth.

Another way to look at it is to understand that our two six volt batteries are wired in series to create one 12 volt battery bank.
 

Geoff W.

Makes Up For It With Enthusiasm
Blogs Author
If looking at the picture of our boat's house bank, that is one (1) bank. We do still have and use the factory 1-2-all master switch, but the second bank is a separate emergency 12 volt agm battery installed under the aft berth.

Another way to look at it is to understand that our two six volt batteries are wired in series to create one 12 volt battery bank.

I currently have two 12-volt deep cycle batteries likely due for replacement here soon...I don't think I have room for a third. So best practice here would be one battery being the "house bank" and one battery being the starter, correct?

Success in installing a battery monitor means understanding the boat's wiring (which is usually haphazard), so that everything goes through the shunt.

Christian, did you take any pics of your Victron shunt install?
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
It's on the engine stringer of the 32-3, next to the (added) bus bar that collects the grounds off the engine block. On the 38 the battery box has (very slightly) more room, so I put it there.

shunt-IMG_1452.JPG
 

toddster

Curator of Broken Parts
Blogs Author
It looks like you might have a dual-bank battery charger hooked up to your batteries. One negative and one fused positive wire to each battery. If so, those should stay where they are. Also one or two other things going directly to the batteries - bilge pump or something, which should be rewired as shown in photo 1. (At least all the grounds should go through a common bus.)

There are lots of ways to hook up battery banks that are all "correct" though opinions vary as to which is "best." Since the small engines in our boats don't require a lot of starting power, a popular option is to run all loads (house and engine) to one big battery bank. A smaller battery, that can be located elsewhere if needed, serves as emergency back-up via the 1-2-all switch.

edit. As far as I can see in the photo, everything on that panel is positive. The negative wires must lead off to a common ground back in the cabinetry somewhere.
 
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toddster

Curator of Broken Parts
Blogs Author
Well - interesting. Maine Sail says I'm wrong about the battery chargers. I find it confusing that he refers to charging sources as "loads." I guess that if you hook it all the the shunt, then you get negative readings during charging.

I'm not sure, but I think I'd like to see my battery usage and my battery charging as separate numbers - not just their sum. Maybe that would require two monitors? Additional reading required.
I'm also not sure that I'd want the positives from the charging sources on the same side of the switch as the loads - I'd put them behind a separate switch.
Hmm... I guess if you have only one wire going to the engine, you've got the starter and the alternator on the same side of the switch anyway.

Happy to be of confusion.
 

Geoff W.

Makes Up For It With Enthusiasm
Blogs Author
So I'm really out of my element here. I had a friend come look today and he said I could just put the shunt between the battery ground and the system ground off the engine block, no bus bar required. I feel like this would make readings inaccurate because the power drain would be through the engine??? I think the panel negative also connects to the engine block, though I've yet to confirm where and how. There's a mysterious second negative hooked up where the battery ground is that looks like it runs to the fuel tank, but why would that be a thing?

Anyways, can I get a sanity check on my understanding of how this works? I drew some diagrams of my current understanding of the boat wiring. If #2 would work and I don't HAVE to figure out how to run everything to a bus right now, that would be awesome.

MVIMG_20181011_205322.jpg
 

toddster

Curator of Broken Parts
Blogs Author
The shade tree mechanic way of hooking up 12V systems was to ground everything to the engine block. The block was acting as your busbar. The thing is, there is only one stud on the engine that is supposed to have a ground wire, and with all the mod cons on 21st Century Digital Boats, the engine turns into a rats nest of sketchy wiring, scabbed on to every available screw that was never meant to support a wire. Thus the recommended practice is to off-load all those extraneous grounds to a dedicated busbar. Think of the busbar as being in the middle of the line between the engine and the battery negative.

The fuel tank and possibly the deck fill are grounded to prevent a static electric charge from developing during fueling. Then there may be bonding wires between your through-hull fittings to prevent electrolytic charge. And maybe a link between your 12V ground and (if any) 110V ground.

If you haven’t got them, it would probably be a good investment to order Nigel Calder and Don Casey’s books on the subject.
 

Kenneth K

1985 32-3, Puget Sound
Blogs Author
Anyways, can I get a sanity check on my understanding of how this works? I drew some diagrams of my current understanding of the boat wiring. If #2 would work and I don't HAVE to figure out how to run everything to a bus right now, that would be awesome.

I'm certainly no expert in electrical systems (somebody go rouse Metzger.....), nor have I ever installed a shunt. I did install a ground bus-bar when I did my engine alternator bracket upgrade. Here are my thoughts:

The idea of the shunt (for a battery monitor) is to measure "ALL" of the current flowing through a particular battery bank. If you have more than one path (more than one ground wire) back to your engine ground, the shunt may be missing the current flow through any alternate paths (ground wires). When I got my boat, it had about 6 or 7 different paths-to-ground. The 3 main ground wires (batt bank #1, bank #2, and electrical panel) had large wires connected to a bolt on the exhaust flange. Several smaller wires were also attached to the small studs on the engine cooling manifold.

1485406025858 (2).jpg

To be able to measure "ALL" the current flow in your bank, I believe you would need to capture all the ground wires to a bus bar (before they are grounded to the engine), then run a single, large wire from the bus bar to the shunt, then finally another single, large wire from the shunt to the engine block (all in a series). That would seem to be the only way the shunt captures ALL the current flowing through a battery bank.

20170616_231619.jpg. Or, to re-use your drawings, something more like this: MVIMG_20181011_205322.jpg

Note, if you have two battery banks, the setup gets more complicated. So somebody who has done this before should probably weigh in. I'm guessing most people only monitor the "house" bank, which would still be wired as discussed above. The second bank would probably require it's own, separate ground to the engine (so that its current does NOT go through the shunt). Admittedly, this is beyond my level of electrical knowledge.

Also see: https://www.youtube.com/watch?v=kxtihQIs9fQ
https://www.youtube.com/watch?v=rKCB4oBqums
 
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Tom Metzger

Sustaining Partner
somebody go rouse Metzger.....

Huh... What's going on? Why wake me? It's a weekend, dammit. Oh, OK, what's the problem?

It's very simple, all of the current going through the house bank has to go through the shunt and no other current can go through it. Simple? Oh, there are details?

Geoff - The Victron monitor can only monitor one bank. You can have more than one battery in a bank which is what many of us do. When my son bought his PS/E-32 I paralleled the two batteries in the well and added a third battery (second bank) in the sail locker for a reserve/starting battery. The two banks are wired through the 1-2-both switch. If you have a fridge I would recommend this arrangement (or similar). If you want to stay with the arrangement you have, two separate batteries, I would designate one of them "house" and the other "reserve". Every year I would switch them so they get equal use.

Looking at your battery photo I see that the negative posts are tied together. Not acceptable. The house bank negative terminal must be connected to the shunt P1 terminal and nothing else can be connected to it. Nothing else can be connected to the P1 terminal. This means that the negative leads from the charger, the bilge pump and the unknown cable must be relocated to the engine ground (or bus). Assuming that you have one charger you do not need separate charger grounds. The P4 terminal of the shunt should both be connected to the engine ground (not a bus) as should the reserve battery negative terminal. If it is more convenient you can connect the reserve battery negative to the P4 shunt terminal.

I believe that the yellow devices you question are fuses. It is good practice to have spares for all of the fuses on the boat.

I suspect that the unknown cable goes back to the stereo to maintain the presets. It probably doesn't need a ground if I am correct.

Fire away with questions.

I'm not sure, but I think I'd like to see my battery usage and my battery charging as separate numbers - not just their sum. Maybe that would require two monitors?

They're called ammeters, and they're cheap. Of course, most chargers already have them, in one form or another.

OK, cocktail time in the east.
 

Geoff W.

Makes Up For It With Enthusiasm
Blogs Author
Thanks for arising from the depths to help, Tom. Seems like harassing you with electrical system questions is an EYO rite of passage.

Geoff - The Victron monitor can only monitor one bank.

Actually I found I just had the wrong one - the BMV-702 has two positive connections so will accept two banks. But I'm thinking when I replace the batteries I'll go with two mounted as a house bank in the battery box and mount the starter/reserve in the aft settee compartment.

Looking at your battery photo I see that the negative posts are tied together. Not acceptable.

For education sake, why is this unacceptable? The boat came this way and seems to operate alright.

The P4 terminal of the shunt should both be connected to the engine ground (not a bus)

Doesn't the "load" side of the shunt need to be connected to the bus to read the other loads, though? As in the panel negative, bilge pumps, and so on. My friend says the same thing - wire it to the engine, but won't the engine block and its various rust/differing metals/etc cause inaccurate readings?
 

Tom Metzger

Sustaining Partner
Thanks for arising from the depths to help, Tom. Seems like harassing you with electrical system questions is an EYO rite of passage.

Yup, but again we are approaching time for my "sundowner", as Philip calls it.

Actually I found I just had the wrong one - the BMV-702 has two positive connections so will accept two banks. But I'm thinking when I replace the batteries I'll go with two mounted as a house bank in the battery box and mount the starter/reserve in the aft settee compartment.

The BMV-702 only reads voltage for the second bank and would be used for your reserve battery. Interesting, on my -602 the two voltage readings are off by about 0.1 volts when reading the same voltage (switching the wires at the shunt). That's a lot when you are interested in a one volt spread. I don't remember which one was closer to my Fluke's reading.

For education sake, why is this unacceptable? The boat came this way and seems to operate alright.

It works for running the boat, but not for the monitor. The charging current and any load on the second battery would introduce an error. In the grand scheme of things it wouldn't matter too much, but it's not right and will get you a demerit, possibly two. Since you are going to install a reserve bank soon I wouldn't change it now.

Doesn't the "load" side of the shunt need to be connected to the bus to read the other loads, though? As in the panel negative, bilge pumps, and so on. My friend says the same thing - wire it to the engine, but won't the engine block and its various rust/differing metals/etc cause inaccurate readings?

The "zero voltage point" (ship's ground) is the engine ground point. The 1/0 cable (I used #2) between the shunt and the engine has effectively zero resistance. That's why you clean the ground point with a wire brush before whomping down on the 3/8" bolt. The reason the battery cable is fastened there is because you want to maintain the best possible path for the starter current. That is the largest and most important current on the boat (not including the fridge motor for keeping the ice frozen for the admiral's cocktails). The bus is connected to the engine ground point so the bus current goes through the shunt to get to the battery.

BTW, your friend is smart, but I question his choice of friends.

OK, 7 o'clock. Sundowner time in the east.
 
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Geoff W.

Makes Up For It With Enthusiasm
Blogs Author
Thanks for all the advice so far in here. I think prematurely buying this battery charger was just the key to a Pandora's box of good electrical upgrades to be done. Not worth monitoring two dying 2013 flooded batteries. If I'm going to replace those, why not upgrade to a bigger house bank and see if I can work a starter battery in. If I do that, then I probably need to upgrade the charger. While I'm in the engine compartment, how about that cockpit engine panel overhaul?

There are a few more threads between now and the close of this one. I'll be back here later to update. I'm gonna have a pro come talk to me in person, though, so even if I embark down a trail of madness, it'll be the RIGHT trail of madness.
 

Tom Metzger

Sustaining Partner
I'm gonna have a pro come talk to me in person, though, so even if I embark down a trail of madness, it'll be the RIGHT trail of madness.

Good choice. The admiral & I can be there whenever you're ready. ;) She has always wanted to visit Seattle and I always carry my out of date PE license.

Keep in mind that the advice you get here is free and we aren't trying to sell you anything. There is a lot of years of experience on EY.org.
 

Tom Metzger

Sustaining Partner
I managed to squeeze shunt into the battery box on that shelf (cable channel?) inside.

Here is where I put the shunt on my son's PS-303/E-32-200. It was taken before the second battery in the house bank was installed so don't try to figure out the wiring.

En Douce 213.jpg
 

Geoff W.

Makes Up For It With Enthusiasm
Blogs Author
Good choice. The admiral & I can be there whenever you're ready. ;) She has always wanted to visit Seattle and I always carry my out of date PE license.

Keep in mind that the advice you get here is free and we aren't trying to sell you anything. There is a lot of years of experience on EY.org.

I'd happily take you up on that, Tom, but how much does the Admiral enjoy the rain? We're almost to the season Seattle is most famous for - "wet".

The advice and participation here is fantastic, even if given half-distracted by the promise of cocktail hour, but having someone there with me in person will be nice so I can ask them over and over, in a louder voice each time, to explain how a 0V ground works in a DC system.

I have an appointment to ramble my half-baked plans to someone on the 29th. I'll let them tell me how much they'd charge for it, and then I can go back to hamfisting my way through the process by myself with a greater sense of financial self-righteousness.

*edit*

Found this last night, seems relevant and useful for anyone coming along later: http://www.ericsonyachts.org/infoexchange/showthread.php?12127-Bus-Bar-for-Engine-Grounds
 
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