Victron BMV 602 Battery Monitor suddenly losing load

[W-G Crew]

We have a Victron Phoenix Multiplus 12v/3000 inverter charger, connected to 5 AGM batteries (675ah) monitored by the BMV 602. For the last five years it has worked very well. Normally whilst cruising the domestic bank of batteries is charged up by the large DC alternator (we have a smaller DC alternator for the starter batteries and an AC alternator with a Dometic travelpower). We normaly lose about 18% charge overnight and the DC alternator begins putting in about 80 ah's dropping to about 16 after 4 or 5 hours cruising. It drops lower slowly and if it remains constant for about 15 mins it is considered full (although i know this is not strictly true). I occasionally sync the BMV, once I now the batteries are as charged as they can be, usually when on shorepower and no real load.

Occasionaly whilst running AC appliances (washing machine, or carpet sweeper) the Amp/hour rate goes up by 10 to 15 % the multiplus taking the extra energy from the AC alternator. This becomes negligble fairly quickly.

Our problem now appears to be that the BMV does not read the output from the alternator. In winter we normally fully charge the batteries and leave some greenhouse heaters in the boat connected to the shorepower. The battery bank has very little load so we visit once a month to run the engine and charge up the batteries amongst other maintenance tasks. On our recent visit the BMV state of charge showed 74% initially but as soon as I started the engine the display changed to 100% in seconds. The rate of charge/discharge showed +3 ah dropping quickly to +1ah not the +80 plus ah as expected and normal. I considered that the alternator wasnt working but it appeared to be doing so, I started up the travelpower and put a load on the AC system and that should have had an impact on the BMV but didnt. I dont think either alternator has failed so my thoughts are that the BMV must have reset itself or shorted out somehow. It later showed a minus value as some of the lights were on in the boat. All indicators show that the BMV is not reading any input. The values held in the memory of the BMV show the same as previously I.E. the total AMP Hours of the battery bank.

It seems like the BMV is not reading the input from the alternators. A blown fuse or similar is what we are hoping is the solution but where to look is our problem before we call in a Victron trained engineer

 

This year the boat has seemed colder but we have used the same regime in other marinas.

 

Any thoughts gratefully accepted

regards

Malcolm & Anne

[Robbo]

Have you changed the battery capacity in the bmv? The percentage is only accurate if that's accurate.

 

Remember battery's lose capacity so you need to find out how much you have left by testing them.

 

My guess is nothing is wrong apart from your batteries have lost capacity so don't need a charge.

 

One way to see if it's the bmv or batteries is too use a clamp meter and check if the amps are similar.

Edited January 19, 2015 by Robbo

[nicknorman]

You've posted quite a bit of information there but I'm afraid I still don't fully get the picture. If your boat is left plugged into shore power, is the Victron not left on in chargeR mode to keep the batteries topped up? That would be the normal way of doing things anyway!

 

The BMV just measures current and voltage, and from that it calculates the state of charge. So the first point is to be sure that all current flowing in and out of the batteries is being sensed by the BMV and displayed as amps in or out. This is easily done. Turn on some load (a few lights), should show amps going out. With shore power disconnected put a load on the inverter (hair dryer etc), should see quite a lot of amps going out. Now plug in shore power with Victron on, should see amps going into the batteries from the Victron. Now disconnect the shore power and start the engine, should see amps going into the batteries from the alternator.

 

Presuming all that is fine, perhaps there is no problem:

 

The BMV has a degree of automatic synchronisation such that if the battery voltage is raised by a charging device (eg alternator), but the batteries are taking very little current (known as the tail current) because they are fully charged, the BMV decides to reset the state of charge to 100%. Typically during several discharge and recharge cycles where the batteries are not fully charged, the BMV gets a bit out of sync and this process resets the state of charge to 100% once the batteries are finally fully charged.

 

Perhaps the batteries were in fact fully charged when you started the engine, but for some reason the BMV was showing only 74% possibly because some charging source is wired to bypass the BMV. So with the voltage raised but the batteries already full and hence taking virtually no current, the software reset the BMV to 100%.

[W-G Crew]

Thank You Robbo and nicknorman,

 

The problem is that the BMV should read a considerable number of Amp Hours when the DC alternator is running, even when batteries are fully charged as there is always a load from a fridge freezer lights etc. When the batteries are full 6 amps is usual normally after 12 hours or overnight the alternator will put in 80 plus amps. So after a months inactivity over Christmas with a very light drain the BMV should show the alternator input.

 

i will test the batteries with a meter on my next visit

 

I have not changed the battery capacity in the BMV

 

I have had the Inverter on in charger only mode and this keeps the batteries topped up but uses quite a lot of electricity to do so and is not good for the batteries left too long so I alternate the practice.

 

Nicknorman your second paragrapgh highlights the problem in a nutshell, the BMV doesnt show amps going into the batteries from either alternator in circumstances you describe

I am aware of the tail current and the effect this has on the Victron electronics and the BMV.

 

Hope this clarifies my initial post somewhat

 

Malcolm

[Keith M]

It would seem that your installation is incorrectly wired

With the engine driven alternator running you should see the amps going into the battery

 

I suspect the fault lies with the starter battery negative wiring by passing the shut

 

Keith

Edited January 19, 2015 by Keith M

[nicknorman]

Presumably the BMV used to show the charging current from the alternator OK? In which case it can't be caused by the charging connection being the wrong side of the shunt - unless you have moved some wires recently?

 

So either there is no current going into the batteries because they are already full, or there is a fault in the BMV. If you have a dc clamp-meter this would help to prove whether or not there is actually current going into the batteries.

 

Presuming there is, as seems likely, then it does suggest that the BMV is not registering current going in. For clarity, can you confirm the BMV is showing current going out?

 

I am not an expert on BMV monitors but I seem to recall the shunts can play up, and I think there have been cases where the BMV only registered current one way as a result. I would carefully examine the shunt and the wiring between shunt and BMV for signs of corrosion etc. I would then try "rebooting" the BMV by completely disconnecting it from the battery+ve and if there is such a thing, doing a "factory reset" followed by reconfiguring it. If all that fails it does rather suggest a fault that is only going to be fixed by replacement of either the shunt or the BMV.

[Paul C]

IF the batteries are fully charged AND the engine is running AND there is a significant 12V load AND the BMV is correctly wired (shunt in the negative connection to the domestic battery bank, and no other connections to the neg connection of this bank) then I'd expect NO significant current to be shown.

 

The reason being, the alternator will supply the 12V load, ie the current will flow from the alternator to the load, not to or from the battery. The alternator, or its regulator, will also regulate the voltage so you'd see no significant variation on this either. Only by having an ammeter in the alternator output wire would you see what current it itself is supplying at any given time.

 

 

the BMV should read a considerable number of Amp Hours when the DC alternator is running, even when batteries are fully charged as there is always a load from a fridge freezer lights etc.

 

 

 

 

I've re-read and basically the above is untrue.

 

Also, why is the fridge/freezer on if you're not at the boat for months on end? Even on shore power, there is no need for it to be on. If you turn it off, prop the door open though.

[Robbo]

Thank You Robbo and nicknorman,

 

The problem is that the BMV should read a considerable number of Amp Hours when the DC alternator is running, even when batteries are fully charged as there is always a load from a fridge freezer lights etc. When the batteries are full 6 amps is usual normally after 12 hours or overnight the alternator will put in 80 plus amps. So after a months inactivity over Christmas with a very light drain the BMV should show the alternator input.

 

 

Are you on shorepower? If so then your charger will be in float mode (batteries are full) and no/minimal charge will be showing on your BMV. The fridge/freezer won't be getting power from the batteries but directly from the charger.

Edited January 19, 2015 by Robbo

[nicknorman]

 

The problem is that the BMV should read a considerable number of Amp Hours when the DC alternator is running, even when batteries are fully charged as there is always a load from a fridge freezer lights etc. When the batteries are full 6 amps is usual

Just to expand on Paul's point on this, as he says the bit quoted above isn't correct. If the batteries are properly full, the charge current should be minimal, just an amp or two. If there is are loads on such as fridge freezer, lights etc then the current for these goes from the alternator direct to them, it does not go via the batteries nor via the BMV. The BMV only shows the current going in and out of the battery. Or if it is not wired like that, it is wired incorrectly. Edited January 19, 2015 by nicknorman

[W-G Crew]

Thank you all,

I suspect the wiring is correct in that we have not made any alterations at all and the system has worked well until now. The Phoenix Multiplus software and electronics does have odd moments. For example using the carpet cleaner can either trip the Dometic travelpower generator or set the state of charge to 100%.

Whilst I accept in theory the load comes from the alternator (not the charger) or batteries when the DC alternator is working. This is never the case in practice . If we were to unplug the shorepower and cruise straight out of a marina the BMV would show a minimum of 4 amps most likely a lot more for the first 20 mins of cruising. Over the years I have tested the loads from most of our appliances and the fridge and freezer take around six amps if on together. As mentioned the BMV shows +/- loads the alternators show up to +120 ah.

 

I cannot confirm that current is going out, I did do all the tests you (nicknorman) suggested yesterday there did not seem to be any significant load being registered in either direction by the BMV.

I suspect the shunt, wiring and PCB attached may have suffered from damp/cold weather. Also there is supposedly a fuse in the system which I shall have to trace and check. Which I will do when i have borrowed a clamp meter on our return to the boat.

 

Thank you all again

Malcolm

[nicknorman]

 

Whilst I accept in theory the load comes from the alternator (not the charger) or batteries when the DC alternator is working. This is never the case in practice . If we were to unplug the shorepower and cruise straight out of a marina the BMV would show a minimum of 4 amps most likely a lot more for the first 20 mins of cruising.

 

Thank you all again

Malcolm

 

This is fairly normal since the shorepower/charger will be in float mode at perhaps 13.25v or so. When you start the engine the voltage from the alternator is perhaps 14.4v and a small amount of current will start to flow into the batteries, how much depending on what the charger float voltage was. But after a while of engine running, I would expect to fall to near zero. The important point is that if you then turn on the fridge, lights etc with the engine still running, the reading on the BMV shouldn't change (unless the load is really big) because the power for these is coming direct from the alternator.

 

Anyway, good luck with fixing it and it is always helpful and interesting if you come back and tell us what was wrong and how you fixed it.

[ditchcrawler]

Didn't Top cat have a problem with the lead between the shunt and panel on one of these some time back http://www.canalworld.net/forums/index.php?showtopic=63235&p=1214919

[Detling]

From the other thread (http://www.canalworl...63235&p=1214919) mention is made of a RJ12 plug with the following wires

1. Blue - voltage sense
2. Orange - not used (except in BMV 602?)
3. Green - current sense (battery end of shunt)
4. Green/White - monitor power negative (load end of shunt)
5. Orange/White - monitor power negative (load end of shunt)
6. Blue/White - monitor power +12V (from battery via fuse)

 

These seem like standard telephone wire colours used in house extension phone sockets, if so the wire could have solid cores and not multistrand cores. This could easily lead to a cracked core in the cable leading to all sorts of weird faults, Victron though are a good company and if they are supplying the lead I would expect it to have stranded cores. If you bought the wire online or at shop though? solid core is more commonly available.

 

I do not have a BMV 60x monitor though so cannot check.