VE Config 3 shows 100% SOC whilst BMV 702 shows 27% SOC

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hope asked Jun 4, '20

VE Config 3 shows 100% SOC whilst BMV 702 shows 27% SOC

I have sailing yacht with a house battery bank of 4 x 150AH Smart Lithium providing 600 ah at 12V, 2 x Multiplus 12/3000/120 Inverter Changers running together, 12/200 BMS, a 10KVA generator (220V) and a BMV 702. All equipment is Victron, installed by a Victron rep in Malta about 14 months ago.

We have just completed a 200nm transit between islands in the Caribbean and the batteries where charged via the drive engine alternator running whilst motor sailing for about around 20 hours. After this the batteries had a voltage of about 13.4V and all the cells were the reading the same. After about 40 hours at anchor we used about 460AH and the BMV 702 shows a voltage of 12.9V, SOC 27%. The VE Config shows 100% SOC and the 16 cells are reading 3.22- 3.23V. The AH consumed and therefore the SOC of 27% seems about right for 40 hours with a draw of 10-12 amps.

My concept for changing to Lithium batteries and adding a second Multi was we would be able get more AH out of the bank - This has been accomplished. Secondly I wanted to be able charge the batteries more quickly than the original AGMs.

Now the VE Config Bus Monitor shows the battery SOC as 100%. The charging output from the Multis after about 3 minutes of starting and on ABS mode is only about 70 amps on the Bus Monitor and about 58 amps the BMV 702 (net charge). This seems very low for this SOC compared to previous charging activity over the last 14 months. I would expect 120 -140 amps+ (gross). Previously the SOC shown on the VE Config would agree with the BMV 702. How do I get the VE Config to show the real SOC? I have tried the usual Microsoft solution - turn all power off on board for 10 minutes then restarted, then turned on the charger via the DMC but the VE Config is still showing SOC as 100%. I used VE Config to reset the Multis to the factory settings and then reloaded the original settings and this made very little difference. I reloaded the latest settings (before reset) but again no real change. I spent most of yesterday reading through the posts in the Forum regarding SOC problems and charging problems but nothing helped. Also went through the manuals for the various equipment and checked the settings on the Multi against these and no joy there either. I am unsure if the erroneous SOC of 100% on the VE Config is having anything to do with the low recharging amps?

What does the group suggest as my next step.

SOC

2 |3000

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Answer 1 · 2020-06-19T01:34:41Z

Michael Riley answered · Jun 19, 2020 at 01:34 AM

@Hope I see you have not had an answer and this is frustrating. We are also on a sailing boat. I am not sure of all the issues or your logic for the approach but can I suggest the following.

1. VE.configure. Not sure why you are referring to this. As far as I know VE Configure is an installer/configuration tool, running on Windows (without some other 'bottle if using MAC), and does not feature in daily management of the system. Victron Connect and Bluetooth or WIFI to Venus XX or BMV7xx would give SOC using the 'available' shunt (connected to whichever unit).

2. SOC is a 'calculation' and cannot be determined by the Multi so far as I know. This is measured by another device (702 in your case) and makes 'broad' calculations about total charge in charge less total out. The 'value' of your 'ZERO' current has a big input into this value over time, particularly if you do not get to an auto 100% state, which in your case is unlikely unless you run the generator until float is achieved. Additionally certain types of loads (e.g. induction cookers, microwaves etc) which have a 'square wave' type current demand) affect this more. I find that SOC %, for Lithium, is a particularly poor management input and so have created a table based on cell voltage that gives me 'energy' I have remaining. This is mostly a peace of mind thing so that I am not jumping to run the generator when I still have plenty of reserve - I have finally got (luck) my 'zero current' value (press to set zero) about right so tracking SOC and Volts is pretty close. See below re 100% SOC.

3. Charing current with 2 x Multi - Unsure however Charging current can be limited by a few things including 'Charge Limit' as set by the Multi (typically using VE.Configure), by a 'temperature' profile (also in the battery configuration of the Multi), or by temperature of the FET's in the Multi. An MPPT also has temperature limits and can be read from the smart battery or by specific cable (temp sense) to the Multi.

4. I do not believe that SOC has any impact on charging value by the Multi - it is the voltage and profile set in the Multi and the Multi knows nothing about SOC.

Suggestions.

a. Try with only one Multi charging. See if you can get this to work (i.e simply turn if off the other one for this exercise). See if you can get the results you want; albeit lower charging current.

b. Try with the other Multi and see if you get i. the same results ii. or what you want to get (if the first did not work)

c. Are you able to get any technical support from the installer in Malta (via email etc)?

d. During commissioning were the various readings in the 70x compared to actuals. I.e. voltage being read and measured by seperate meter were accurate etc. i.e. was the shunt correctly installed, using the correct resistor value etc.

Hope your debugging is progressing.

1

2 |3000

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hope commented · Jun 19, 2020 at 07:26 PM

@Michael Riley

Yes, a bit disappointing, but thanks for your input. I am also very disappointed in the Lithium batteries in general. The old house batteries were AGM and never needed attention and until one failed after 5 years of 24/7 use- These lithium batteries and the BMS have given trouble from the start. The BMS was shutting down the system when the batteries were being charged by the engine alternator. This happened whilst maneuvering causing lose of control of the boats thrusters and all instruments. It had also happened whilst travelling during the day and at night which was obviously the worse case scenario. This, I found eventually, was due to the BMS over heating. This other shutdown problem due to one cell going below the shutdown value caused problems for weeks before I could find the issue. With the AGM's I never experienced a shutdown, the charging was simple and I didn't need to make any changes to anything - just charge and forget. From my experience over the last 12 months I would not fit Lithiums again. In hind sight I would have been much easier, cheaper and less stressful to have replaced the old AGM's with new AGM's.

Once we had the upgraded equipment installed and then commissioned by the Victron Dealer in Malta he suggested I get a Mk3 Interface and download the required software to make changes to the setup of the Multis etc using Config 3. He knew we would be in lots of places in the next 5-6 years where there would be no Victron dealers for support. His Set Up was not really suitable for our cruising style. It took a while to get a hold of a Interface but once I had same I could make changes to the Multis set up.

I am still trying a few mods to see if I can get better charging performance out of the Multis. The 2 Multis are set up as Master and Slave and will not operate individually unless I change their set up to be stand alone via Config 3. I tried turning one off and the Digital Multi Control panel came up with an error message and the Multi still turned on would not operate. If I changed them to be stand alone I would then need to reconfigure them back to dual operation.

The SOC information from VE Config is apparently from the Multis. The software displays a VE Bus Monitor which shows Incoming (shore power) AC Voltage, amps used and frequency, It also shows AC voltage, amps frequency out of the Multis. It also shows the DC voltage and amps out of the charger side of the Multis. This monitor also shows SOC and in this case it shows 100% regardless of the actual battery voltage or SOC displayed on the BMV 702.

So I have no idea why the charging drops so quickly and well before the batteries have reached their float voltage. The batteries do not appear to be getting hot during charging. But we are in the tropics so ambient during the day is 32 C. Today I moved the batteries so there is some space between them to assist with cooling but I am not sure this was necessary.

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