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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

Hi all, sorry to jump on this but you guys seem to know what you are on about. I have just installed a NASA BM1, I have 2 110ah batteries connected in parallel (connected neg to neg), wired up correctly with NO other negatives on the batteries part from the wire to the black and white side of the shunt. When everything is turned off the battery is displaying discharge of 0.01amps and when charging it goes pass 100% (to roughly 105%). I have a 100w solar panel installed (it’s giving me 0.4amps of charge due to living in Yorkshire with crap weather this time of year). The neg from the solar is also Connected to the yellow end of the shunt. Should the neg from both battery’s be connect to the black and white end of the shunt or connected together with one wire going to the black and white end? Is all this right? Have I done something wrong. Thanks in advance everyone.

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