Wiring shunt to battery bank

[Bugsworth Tippler]

I have recently been given a Victron battery monitor BMV600 and am looking to add it to the boat.

 

The installation of the shunt seems simple enough if you have one battery but with a bank of three domestic batteries there are options available and I am concerned to choose the best one.

 

Looking at the current wiring of the domestic batteries it doesn't seem that the batteries are currently wired in the best configuration (though I'm not sure about that). I'm aware of the Smartgauge site and Option 2 where the positive and negative 'take-offs' should be diagonally opposite one another and that seems to be what I have presently (1st image)

 

Intuition suggests that the alternator connections ought to be made in a similar sort of way but that is not presently the case; they being connected to the middle battery of the three.

I'm thinking that the shunt should be added with some minor changes (as shown in image 2) but am not at all sure about this.

 

I've looked at info about alternators/charging/etc on this and other sites but have not found any info that gives me the confidence to proceed with this change. Any comments would be most welcome.

 

There are two alternators on the Isuzu engine which appear to charge the starter and domestic batteries separately.

 

Thanks in anticipation of some helpful advice

[Robbo]

Nothing but the batteries are connected to the shunt near B1, so the alternator and engine block go on the other side of the shunt with the CPC.  The starter battery negative is on the correct side of the shunt as you have it.

 

Basically if anything other than the shunt are connect to the negative side of the batteries then it's not been picked up by the shunt.

Edited August 6, 2018 by Robbo

[Robbo]

This is the correct way....

[TheBiscuits]

1 minute ago, Robbo said:

This is the correct way....

... and note that if you care about the starter battery loads (why would you?)  you will need another shunt (and probably another meter, too).

[Sea Dog]

The single battery to the left is your starter battery. It's negative should be connected to the domestic negative, but... Hang on, you need a diagram and I can't do that from the phone, but someone will provide one shortly. There's sure to be one in the Victron bmv instructions on line though.

 

Suffice to say, on one side of the shunt should be the domestic battery negative ONLY. Nothing else - no, not even that (whatever it is you thought of)! All the other negative connections (all charging sources, all loads and any link to other batteries) should be on the other end, so that NOTHING goes in or out of your domestic batteries without going through the shunt. Ok?

 

For 3 batteries in parallel as you have, connect input/output positive and negative at opposite corners as you have already sussed. Other combinations work, but this works well and is both easy to do and it's dead clear what's going on.

[Bugsworth Tippler]

Thanks to all who have replied, especially Robbo for taking the trouble to correct the diagram. I think everyone is in agreement and the explanations seem to make sense to me (with my limited knowledge). I'll make the changes with a lot more confidence now.

[Bugsworth Tippler]

Hello again,

 

After such a fantastic response to my original query perhaps I might slip in an additional question?

 

The positive supply cable to the domestic battery bank could got to one of three terminals (A, B or C in image 3). Is there a best option?

[rusty69]

C

http://www.smartgauge.co.uk/batt_con.html

[Sea Dog]

^^^^ C - like wot Rusty said. Also, put your thin red supply line from the shunt there too - it'll work fine on any but it keeps the installation simple rather than having numerous connections (there isn't really 2 as in your diagram where you show t'other going to the starter battery, is there?)

[Bugsworth Tippler]

Thanks again.

33 minutes ago, Sea Dog said:

^^^^ C - like wot Rusty said. Also, put your thin red supply line from the shunt there too - it'll work fine on any but it keeps the installation simple rather than having numerous connections (there isn't really 2 as in your diagram where you show t'other going to the starter battery, is there?)

The thin lines are what I called the positive supply cables earlier as that's what they are called on the Victron BMV600 leaflet. Hope that didn't cause any confusion. There are two, one to the starter and one to the leisure battery/batteries. Hope the diagram is now correct!

[Bugsworth Tippler]

Oops. I've just discovered it's a BMV 602 which explains the second lead I suppose.

[Sea Dog]

2 hours ago, Bugsworth Tippler said:

Oops. I've just discovered it's a BMV 602 which explains the second lead I suppose.

It does indeed!  The main info is about the domestic batteries and comes courtesy of the shunt, giving instantaneous readings of amps (in or out) and Volts from which it works out amp hours used and then battery percentage state of charge and similar stuff (the latter all a bit unreliable).  The other function, which comes in the 692 version, simply monitors the starter battery voltage, which is generally enough.

 

Your diagram now looks right, although there ought to be battery isolation switches involved just off the page.

[Iain_S]

  ... although I am a bit surprised by a negative lead going to D+ on the alternator ...

[Bugsworth Tippler]

30 minutes ago, Iain_S said:

  ... although I am a bit surprised by a negative lead going to D+ on the alternator ...

Thanks, I'll check that when I next go to the boat.

 

I assume it ought to be D- (added after a little research).

Edited August 6, 2018 by Bugsworth Tippler
Researched alternators.

[system 4-50]

Aside from the OP's problem, can somebody explain for simple folk like myself why the little leads from the shunt don't go to a meter?  Is it more than a plain shunt?  

[Robbo]

4 minutes ago, system 4-50 said:

Aside from the OP's problem, can somebody explain for simple folk like myself why the little leads from the shunt don't go to a meter?  Is it more than a plain shunt?  

The leads are for monitoring the voltage of the batteries.  A twisted pair cable like a Network cable goes to the meter.

Edited August 7, 2018 by Robbo

[Tony Brooks]

13 hours ago, Bugsworth Tippler said:

Thanks, I'll check that when I next go to the boat.

 

I assume it ought to be D- (added after a little research).

I bet that IF your alternator has a genuine D- which I very much doubt then it will be connected to the engine block or starter negative terminal. I am far from sure that on the vast majority of our alternators that cable is even required - happy for an explanation as to why this is not correct though. it just might apply to certain genuine insulated return alternators.

[Bugsworth Tippler]

25 minutes ago, Tony Brooks said:

I bet that IF your alternator has a genuine D- which I very much doubt then it will be connected to the engine block or starter negative terminal. I am far from sure that on the vast majority of our alternators that cable is even required - happy for an explanation as to why this is not correct though. it just might apply to certain genuine insulated return alternators.

I'll investigate and report further on the alternator wiring later today after a visit to the boat. IF the original diagram WAS correct and the negative lead from the battery does go to a D+ terminal on the alternator I'd be interested in hearing why this is incorrect. The system seems to have been working reasonably well and despite a slightly loose fan-belt (only just discovered), the hot weather with an amp-hour hungry fridge, and several days of only 2-3 hours cruising the batteries 'seem' to be OK. The reason for adding the battery monitor is, of course, to get a better idea of their condition.

[Tony Brooks]

8 minutes ago, Bugsworth Tippler said:

I'll investigate and report further on the alternator wiring later today after a visit to the boat. IF the original diagram WAS correct and the negative lead from the battery does go to a D+ terminal on the alternator I'd be interested in hearing why this is incorrect. The system seems to have been working reasonably well and despite a slightly loose fan-belt (only just discovered), the hot weather with an amp-hour hungry fridge, and several days of only 2-3 hours cruising the batteries 'seem' to be OK. The reason for adding the battery monitor is, of course, to get a better idea of their condition.

If you connect D+ to any negative then if you are lucky ir will short out the alternator rotor and  regulator and prevent the machine energising. The charge warning lamp will also stay on all the time.

 

If you are unlucky the alternator will energise and you will short out and destroy the three small field diodes so  new alternator.

 

 

IF the small wire is shown as going to D- then that makes a kind of sense if its a true insulated return alternator but I am trying to think of one that has a true D-. Lets suppose you do ave a D- and you put that extra wire on it, s you now have two cables on the terminal. Then it would just be in parallel wit the main negative cable.

 

Some rarer alternators may have a D- that connects to the voltage regulator but if so that extra lead may cause uncontrolled output or burn something out.

[Bugsworth Tippler]

5 minutes ago, Tony Brooks said:

If you connect D+ to any negative then if you are lucky ir will short out the alternator rotor and  regulator and prevent the machine energising. The charge warning lamp will also stay on all the time.

 

If you are unlucky the alternator will energise and you will short out and destroy the three small field diodes so  new alternator.

 

 

IF the small wire is shown as going to D- then that makes a kind of sense if its a true insulated return alternator but I am trying to think of one that has a true D-. Lets suppose you do ave a D- and you put that extra wire on it, s you now have two cables on the terminal. Then it would just be in parallel wit the main negative cable.

 

Some rarer alternators may have a D- that connects to the voltage regulator but if so that extra lead may cause uncontrolled output or burn something out.

So it can't be going to the D+ terminal, but what does it do to? The mystery deepens.... now I'm off to find out!

[Tony Brooks]

32 minutes ago, Bugsworth Tippler said:

So it can't be going to the D+ terminal, but what does it do to? The mystery deepens.... now I'm off to find out!

That question needs addressing to the makers. I suspect it is D- on a few alternators.

[Bugsworth Tippler]

More careful inspection of the alternator shows that the thick cable going to the negative on the battery is not from the D+ terminal but another beneath it (and very close to the D+ label - which is probably why I made the original error in my diagram). This terminal does not appear to be identified.

 

The alternator on the Isuzu 35 engine is labelled 90AMP/12V alternator, HMI Pt No: 900383-ALS.

 

 

There is nothing on the W terminal and a thin yellow/black wire goes from the D+ terminal. I think it ends up attached to a battery warning light on the control panel.

 

I've changed the last diagram image to provide, hopefully, a more correct version.

 

 

There will be a lot of thick cables going to one shunt terminal. Is there a neat way of doing this?

 

Thanks again to everyone who has been so helpful.

 

Ian

[Robbo]

13 minutes ago, Bugsworth Tippler said:

There will be a lot of thick cables going to one shunt terminal. Is there a neat way of doing this?

You can use a bus bar, like from the likes of BlueSea.   

[Tony Brooks]

52 minutes ago, Bugsworth Tippler said:

More careful inspection of the alternator shows that the thick cable going to the negative on the battery is not from the D+ terminal but another beneath it (and very close to the D+ label - which is probably why I made the original error in my diagram). This terminal does not appear to be identified.

 

The alternator on the Isuzu 35 engine is labelled 90AMP/12V alternator, HMI Pt No: 900383-ALS.

 

 

There is nothing on the W terminal and a thin yellow/black wire goes from the D+ terminal. I think it ends up attached to a battery warning light on the control panel.

 

I've changed the last diagram image to provide, hopefully, a more correct version.

 

 

There will be a lot of thick cables going to one shunt terminal. Is there a neat way of doing this?

 

Thanks again to everyone who has been so helpful.

 

Ian

 

Well in my view as long as the main battery negative cable is thick enough, and it should be, there is no reason that negative cable on the alternator has to run to the shunt. I think you could connect it to the same point on the engine  as the main engine battery negative cable.  You do not show the main engine battery negative on your diagram but it must have one on the engine battery negative terminal. Ah just seen that you do buy it runs to teh shunt. I think it can justa s well go to the engien batter. Whichever position you put t in et shunt will not monitor the engine charging current

 

Then the main engine battery negative would also act as the 90 amp alternator negative via the engine negative and the link to the shunt.

 

That gets rid of one cable on the shunt and now it looks as if you an get rid of two.

 

Very happy to have it explained why I am wrong though.

 

[Robbo]

4 minutes ago, Tony Brooks said:

 

Well in my view as long as the main battery negative cable is thick enough, and it should be, there is no reason that negative cable on the alternator has to run to the shunt. I think you could connect it to the same point on the engine  as the main engine battery negative cable.  You do not show the main engine battery negative on your diagram but it must have one on the engine battery negative terminal. Ah just seen that you do buy it runs to teh shunt. I think it can justa s well go to the engien batter. Whichever position you put t in et shunt will not monitor the engine charging current

 

Then the main engine battery negative would also act as the 90 amp alternator negative via the engine negative and the link to the shunt.

 

That gets rid of one cable on the shunt and now it looks as if you an get rid of two.

 

Very happy to have it explained why I am wrong though.

 

If the OP doesn’t want to use one cable for engine/alternator then moving the engine block negative to the starter battery would be my choice as this negative is the only one used by the starter battery.

Edited August 7, 2018 by Robbo