BMV-600 battery monitor help needed

[Waynerrr]

Last week I fitted a new BMV-600 to my boat and was pleased to see it working straight away. I inputted the Ah of my battery bank (330Ah (3 x 100Ah)) but did not synchronise it (it appeared to be working correctly anyway so didn't bother). Having been away for a week I went back today to find the state of charge indicator still showing 100%, which I found hard to believe. I turned on the invertor, charged my phone, put some lights on and the radio and ran the heating. Still the monitor wouldn't show any amps drawn or a decrease in the SOC. However, the volts had dropped from 13.2v from when I'd arrived to 10.2v (in less than 30 minutes).

 

The manual only shows the monitor on a single battery so I guessed with one part of the instructions. It says to connect the negative pole to the shunt and the shunt to the "Battery negative (system ground)". I have connected the negative pole to the shunt and the shunt to the negative pole of the next battery in my bank. Is this correct?

 

I went to great effort to create a diagram but for some reason I can't get images to work here...

 

I also have a starter battery which is connected to the bank via the negative pole only and a 125w solar panel connected via a regulator. The regulator confirmed the bank required charging when it was down to 10.2v. Could the batteries be knackered as well? They're about 18 months but weren't treated particularly well.

[bottle]

Not sure what you have done but to wire a shunt:

 

All the negatives from the boat (that normally go to the battery bank) should be connected to one end of the shunt.

 

The other end of the shunt has to be connected to the battery terminal (where all the negatives were connected)

 

The two small terminals are connected to the BVM

 

The battery bank should be wired so that all the positives go to one end of the bank and all the negatives to the other end.

 

See http://www.smartgauge.co.uk/batt_con.html (lots more info on that site)

[Waynerrr]

This is how they're connected to the shunt (this doesn't include the starter).

 

https://www.dropbox.com/s/n6ltojoarwow00s/bmv_ne.png

[bottle]

Wrong, see my post above and look at the wiring diagrams in the link

[nicknorman]

The key thing is to have everything going into and out of the domestic batteries going through the shunt. But not anything that is not to do with the domestic batteries (ie anything to do with engine or bow thruster batteries).

 

To achieve this, you must have all the domestic battery negatives connected together - obviously! But NOT also connected to the engine battery negative. Then one end of the shunt must connected to one of the domestic battery negatives, preferably but not essentially the terminal that is diagonally opposite where all the positive feeds are (helps to keep the batteries balanced if you have relatively thin battery interconnects).

 

Then everything to do with domestic supply and generation negatives are connected to the other side of the shunt. So ABSOLUTELY NOTHING AT ALL is connected to the domestic battery negatives except the shunt. Nothing!

Depending on your charging arrangements it may be better to take a separate negative (thick) cable from starter battery -ve to the engine, or connect it to the other side of the shunt.

 

That's it. Just make sure the polarity at the shunt is correct so that it counts current going into, and out of, the batteries in the correct sense. Otherwise the meter will be pegged at 100% during discharge - and of course start to decrease during charge!

Edited December 15, 2013 by nicknorman

[Waynerrr]

I saw that, thanks. So how would I connect the shunt then? Keep the batteries as they are in method 1 in the link you provided and they simply feed the shunt off of it? Currently I'm running the negative through the shunt which now looks very wrong.

 

This is a diagram from the manual http://www.victronenergy.com/upload/documents/Battery%20monitor%20quick%20install%20guide_REV10_05-07-2007.pdf

Edited December 15, 2013 by Waynerrr

[bottle]

I saw that, thanks. So how would I connect the shunt then? Keep the batteries as they are in method 1 in the link you provided and they simply feed the shunt off of it? Currently I'm running the negative through the shunt which now looks very wrong.

 

As per my first post.

 

Remove the shunt and put all the wiring back as per Method 1 (as that is what you have)

 

Now take all the negatives of the end battery and connect them to the shunt.

 

Connect the other end of shunt to the empty negative terminal on the battery.

[nicknorman]

I saw that, thanks. So how would I connect the shunt then? Keep the batteries as they are in method 1 in the link you provided and they simply feed the shunt off of it? Currently I'm running the negative through the shunt which now looks very wrong.

 

This is a diagram from the manual http://www.victronenergy.com/upload/documents/Battery%20monitor%20quick%20install%20guide_REV10_05-07-2007.pdf

Just treat your group of 3 domestic batteries as if they were the one battery in the diagram. Connect all positives together , and all negatives together (as they presumably were before you started) and then connect one end of the shunt to one of the battery negative terminals, connect all the wires you took of the battery negative terminals (apart from the interconnects) to the other end of the shunt.

[Waynerrr]

Ok, thank you very much both, that sounds a lot clearer now.

[by'eck]

Last week I fitted a new BMV-600 to my boat and was pleased to see it working straight away. I inputted the Ah of my battery bank (330Ah (3 x 100Ah)) but did not synchronise it (it appeared to be working correctly anyway so didn't bother). Having been away for a week I went back today to find the state of charge indicator still showing 100%, which I found hard to believe. I turned on the invertor, charged my phone, put some lights on and the radio and ran the heating. Still the monitor wouldn't show any amps drawn or a decrease in the SOC. However, the volts had dropped from 13.2v from when I'd arrived to 10.2v (in less than 30 minutes).

 

The manual only shows the monitor on a single battery so I guessed with one part of the instructions. It says to connect the negative pole to the shunt and the shunt to the "Battery negative (system ground)". I have connected the negative pole to the shunt and the shunt to the negative pole of the next battery in my bank. Is this correct?

 

I went to great effort to create a diagram but for some reason I can't get images to work here...

 

I also have a starter battery which is connected to the bank via the negative pole only and a 125w solar panel connected via a regulator. The regulator confirmed the bank required charging when it was down to 10.2v. Could the batteries be knackered as well? They're about 18 months but weren't treated particularly well.

 

You have connected the shunt in the wrong position so the main current is not running through it hence display stuck at default 100% SOC.

 

Your battery bank will be created by the three batteries wired in parallel - the three negative terminals will be looped to each other and the same for the positives. There should be a single feed out to from opposite ends of the bank for the positive and negative feeds to equipment/main panel. Its the single negative feed you need to identify and break into to fit the shunt.

 

This should be before a negative loop to starter battery if fitted, since we don't want to monitor the current flow to/from that as well.The shunt should be as close as possible to the battery bank and wired as per instructions so that flow out of batteries displays as a negative current value and obviously positive for flow into batteries.

 

There should be no other connections between shunt and domestic battery negative feed.

 

See below to see where shunt is inserted on this five battery bank, noting that it only measures service battery bank current flow as mentioned above.

 

[bottle]

Wayne

 

When you get the shunt sorted, you may want to think about wiring your battery bank as in Method 2 (in the link I gave you in post #2)

 

Reading that page will also tell you why.

[smileypete]

One way to do it is connect domestic batt bank negative return to shunt ONLY, then ALL the domestic negative returns to the OTHER side of shunt. The ONLY thing connected to the negative side of the batt bank is the shunt.

 

Or if you have a hull earth bond stud near the batts ALL the domestic negative returns can go back to that as it's usually quite sturdy, then the domestic batt bank negative return to shunt ONLY, then the OTHER side of the shunt connects to the hull earth bond. Again the ONLY thing connected to the negative side of the batt bank is the shunt.

 

If it's clear as mud please say and I'll do a diagram.

 

cheers, Pete.

~smpt~

Edited December 15, 2013 by smileypete

[Richard10002]

One way to do it is connect domestic batt bank negative return to shunt ONLY, then ALL the domestic negative returns to the OTHER side of shunt. The ONLY thing connected to the negative side of the batt bank is the shunt.

 

Or if you have a hull earth bond stud near the batts ALL the domestic negative returns can go back to that as it's usually quite sturdy, then the domestic batt bank negative return to shunt ONLY, then the OTHER side of the shunt connects to the hull earth bond. Again the ONLY thing connected to the negative side of the batt bank is the shunt.

 

If it's clear as mud please say and I'll do a diagram.

 

cheers, Pete.

~smpt~

That's exactly what I did when I fitted a NASA BM2 monitor. 1 cable from shunt to negative battery terminal. All cables that would normally connect to the negative battery terminal connect to the other end of the shunt. Fairly straightforward really.

[by'eck]

One way to do it is connect domestic batt bank negative return to shunt ONLY, then ALL the domestic negative returns to the OTHER side of shunt. The ONLY thing connected to the negative side of the batt bank is the shunt.

 

Or if you have a hull earth bond stud near the batts ALL the domestic negative returns can go back to that as it's usually quite sturdy, then the domestic batt bank negative return to shunt ONLY, then the OTHER side of the shunt connects to the hull earth bond. Again the ONLY thing connected to the negative side of the batt bank is the shunt.

 

If it's clear as mud please say and I'll do a diagram.

 

cheers, Pete.

~smpt~

 

Diagram already shown above here Pete

[Waynerrr]

Thank you all, I think I understand. I've done a couple more diagrams just to see if I understand it correctly. I think they're basically the same but one would be easier for me as I don't have to buy any more cables.

 

Method a https://www.dropbox.com/s/us14hxqi5agmn3i/bmv_2.png

Method b https://www.dropbox.com/s/48yagae5ej4fct4/bmv_3.png

 

If neither of these is correct I'd really appreciate a diagram similar to mine

 

The only thing I'm not clear on, especially after reading smileypete's reply, is where do I put the solar panel negative? To the battery bank or to the opposite side of the shunt?

 

Many thanks

[nicknorman]

Either would work, but neither is optimal. Option b with either the shunt, or the +ve takeoff moved to the other end of the bank, would be best. All negatives should be connected to the non-battery end of the shunt, that includes solar panels.

[smileypete]

I'd do method b, BUT move the connection from batt bank to shunt to the top end of the bank, so it's diagonally opposite the takeoff on the positive side of the bank.

 

The solar regulator negative return (and other negative returns) should go to the end of the shunt that is NOT connected to the batts.

 

cheers, Pete.

~smpt~

Edited December 17, 2013 by smileypete

[Waynerrr]

Great, thank you all

[Waynerrr]

So I managed to fit this as suggested and it did indeed appear to work, however (predictably), the monitor is giving out some odd readings. SOC doesn't really seem to change despite the V going down. The volts go down so rapidly I think the batteries are FUBAR. I had 3 LED lights on for an hour plus I ran a jigsaw off the inverter for about 5 minutes: the V went from 13.2 to 10.6 (but the SOC remained at 100% - it only went down to 99.3% when I was charging the batteries!). So, is the monitor behaving oddly because the batteries are knackered or is there another reason? Incidentally, I sync'd the system when it probably wasn't fully charged.....

[by'eck]

If the SOC is going down when you charge batteries, you have connected the shunt the wrong way around. This would explain why it doesn't change from the calibrated 100% SOC on load, as the reverse current measurement will try and increase this reading which it can't do since batteries can't be above 100%.

Just reverse battery connections to cure this issue.

 

After doing this, check the current reading is negative when there is a drain on the battery and positive when its being charged.

 

Check also you set the battery capacity, Cb in setup menu, to the correct value for your bank size - 330 Ah in this case (default 200 Ah).

Your voltage measurements following such a short discharge, suggests the batteries may be shot, but get the monitor working correctly first, then fully charge batteries. Every time the SOC reaches 100%, it will effectively recalibrate itself, but this won't allow for diminished battery capacity.

 

[Robbo]

So I managed to fit this as suggested and it did indeed appear to work, however (predictably), the monitor is giving out some odd readings. SOC doesn't really seem to change despite the V going down. The volts go down so rapidly I think the batteries are FUBAR. I had 3 LED lights on for an hour plus I ran a jigsaw off the inverter for about 5 minutes: the V went from 13.2 to 10.6 (but the SOC remained at 100% - it only went down to 99.3% when I was charging the batteries!). So, is the monitor behaving oddly because the batteries are knackered or is there another reason? Incidentally, I sync'd the system when it probably wasn't fully charged.....

 

Check the "I" display, if your not charging the batteries and using them it should have a minus amp figure, if your charging them it should be a positive figure.

 

To check how much capacity you have, charge until the charger goes into float mode (then sync the BMV). Then use the batteries as you would do normally, check the CE display, when it gets to something like 100amps, remove all load from the batteries for at least an hour and then measure the voltage to tell you what percentage of charge there in. You should then be able to work out how much capacity they have.

 

Your voltage measurements following such a short discharge, suggests the batteries may be shot, but get the monitor working correctly first, then fully charge batteries. Every time the SOC reaches 100%, it will effectively recalibrate itself, but this won't allow for diminished battery capacity.

 

 

 

I found that some of the settings are a little bit too high, so I've changed the following..

 

It: 1 (default 4)

CEF: 84% (default 90)

 

"It" is a percentage of Cb (capacity), combine this with Vc and it will detect when the battery is charged when the amount of amps falls below this %

"CEF" I found 90% was too high, so I've lowered it. I'm trying 84% too see if right.

"Vc" I haven't changed this, but reading the instructions again looks like I should as my float voltage is 13.2, which is what Vc by default is set too. I think 13v is what mine needs to be set to.

[MoominPapa]

Just reverse battery connections to cure this issue.

I'm sure you meant to say "just reverse the SHUNT connections". OP, DO NOT reverse the battery connections, that would be a Bad Thing to do.

 

If shunt is the type with two fat connections and two thin wires to the meter, then you can reverse either set. If it's the type with built in electronics and a modular plug on the cable to the meter, then you'll need to reverse the fat cable connections. To check it's right, a discharge should read as a negative number on the amps read-out, and a charge as a positive number.

 

MP.

Edited December 24, 2013 by MoominPapa

[nicknorman]

CEF, and It depend on battery condition. Ours is currently 93% (automatically calculated by our Mastervolt monitor) and I have It set to 1% (4A) but when the batteries age, CEF is likely to fall and It may need to be increased.

 

Anyway, it does sound like OP's batteries are knackered.

Edited December 24, 2013 by nicknorman

[Robbo]

CEF, and It depend on battery condition. Ours is currently 93% (automatically calculated by our Mastervolt monitor) and I have It set to 1% (4A) but when the batteries age, CEF is likely to fall and It may need to be increased.

 

Anyway, it does sound like OP's batteries are knackered.

 

What type of batteries do you have? Mine are Trojan T105's so may be a lower CEF than a leisure battery would be. (Same reason a leisure battery can give amps, it can also take em!). However I've just got the monitor so early days..

Edited December 24, 2013 by Robbo

[smileypete]

If the batts state of health are unknown, maybe it'd be good to set a very conservative number for bank capacity, say a quarter of what batt rated capacity is.

 

Then if batt 'resting voltage' indicates that state of charge is higher than what's on the monitor, bump up the capacity setting a bit.

 

Table of resting voltage vs state of charge is in The Battery FAQ here:

 

http://jgdarden.com/batteryfaq/carfaq4.htm#ocv_soc

http://www.batteryfaq.org/

 

Also charge efficiency could be a lot lower than anticipated for a less than healthy batt so if state of heath is unknown maybe be a bit conservative with that setting too, say 70-75%.

 

Then if batt charge current tails off to a steady 'finishing current' level indicating that state of charge is 100%, and the monitor shows less, bump up the charge efficiency factor too.

 

cheers, Pete.

~smpt~

Edited December 24, 2013 by smileypete