This site is now in read-only archive mode. Please move all discussion, and create a new account at the new Victron Community site.
Hi
I have a 2 week old installation of OzPv gel batteries charged by a Victron MPPT 250/100, a Multiplus 5000Va inverter and ColourGX. I get no battery SOC even tho the MPPT knows when to move to absorb'float etc during daytime and the Multiplus knows how much charge taken from the batteries. Is there a setting for CGX to display SOC or do I need more hardware?
Thanks. You guys do a great job!
Clve
Unless you have a setup with ESS active the MPPT and Multiplus act independently.
As long as you have no other DC loads in the system you can use the battery monitor functionality within the Multiplus to consider the charge current from the MPPT and keep track of battery SOC %.
However, to do this you must;
1- Use VE.Configure and a MK3 to USB cable to enable and configure the battery monitor in the Multiplus
2- Then using the CCGX select the Multiplus as the battery monitor
Link to CCGX manual:
https://www.victronenergy.com/live/ccgx:start
Link to VE.Configure manual:
https://docs.victronenergy.com/veconfigure.html#general-settings
Hi
That's great thankyou. What does ESS active mean for my offgrid home? Should I use the ESS active as you mention above or should I use the cable suggested above?
ESS stands for Energy Storage System.
It's a powerful integration and control system for grid connected systems, but not suitable for off grid setups.
You can read more about it here;
https://www.victronenergy.com/live/ess:design-installation-manual
Thanks again Mark! Done and now have SOC but :
Night 1 SOC dropped to 90% as expected
Day 2 SOC remained at 90% even tho MPPT moved to float after boost voltage reaching 58.2V
Night 2 SOC dropped another 10% to 80%
Day 3 SOC climbed to 85% after MPPT moving to float for several hours after plenty of charge
Any ideas why Opzv SOC not returning to 100% after plenty charge and Multiplus set to C120 rate for full charge?
I am outside Sydney and temp range 0-15deg and understand battery capacity might drop by 15% in cold winters?
No problem & great to hear that you got the battery monitor function going.
To understand whats going on a bit better could you possibly share some screen images of your;
- MPPT charge settings from Victron Connect
- Multiplus battery monitor setting from VE Configure
Also if you have a data sheet for your batteries attach it.
I also just realized that you entered the C120 battery capacity, normally the C20 capacity should be entered into the battery monitor. As the C20 capacity will be lower it will help with your issue.
Great thanks Mark. Is it usual to use C20 even though my overnight discharge rate is only 10-15% and closer to C120?
For a proper battery monitor (BMV) it is recommended in the documentation to use the 20h battery capacity rating and it then continuously uses peukert's law to compensate for different actual discharge rates.
I'm not totally sure if the simplistic battery monitor functionality in the Multiplus uses peukert's law compensation or not.
Regardless, I expect that using a battery capacity that align with the intermittent periods of high current draw (that is not continuous) would provive a more appropriate/accurate representation of SOC% delta than using a battery capacity that aligns with the 'average' current draw over the entire day.
Either way it seems that you have a disconnect with the indicated SOC%, which may be real or not. If not then the delta needs to be compensated somehow and lowering the battery capacity is one way.
Using the Multiplus battery monitor functionality will not be as accurate as a BMV (which measures all current into & out of the battery via the shunt) but you should be able to get it to track the real SOC% a bit closer.
So if you can share some screen images of the current charger & battery monitor settings then maybe that will provide some more insight.
I think that the main thing to check is the current flow into the battery just BEFORE the MPPT or Multiplus ends the absorption charge phase and switches to float has gradually reduced down to below ~2% (even ~1%) of the battery C20 capacity.
If there is higher current still being accepted by the battery just BEFORE absorption phase ends, then its an indication that the battery is not being fully recharged and I would recommend to increase the absorption time to correct this.
Hi clive,
it may be not the solution for you problem but I can share my own experience with you.
For a few years I used the Multiplus SoC calculation with a small battery bank (24V/330Ah) and it worked quite well.
A few month ago I upgraded to OPzV batteries (24V/1200Ah) and with my system it was not possible to get reliable SoC readings anymore. The main problem with the Multi SoC is, that everything is based on assumptions. "Bulk finished" at a certain voltage is assumed to be 85% (or whatever entered in VEConfig). After absorption time, it is assumed that SoC is 100% (who knows how long it should be and what it really is when not completed). The next day you start with a wrong SoC and the game starts again. I think the error effect gets bigger and bigger depending on the battery size.
After a few days (with not so sunny wheater) my SoC was completly off the way. Neither the Multi nor I knew the real SoC of my expensive battery bank (according to battery voltage it was quite low).
This was the reason why I decided to buy a BMV712 battery monitor. With this item you can configure very specific parameters when the batteries are really full (voltage, current and time). This works very good and the SoC calculations are much more accurate (peukert, more charge sources etc). So this would be my advise for you.
Best regards
Rainer
Hi mark
Thankyou for your comments above. In reply you can see
1. Even though MPPT max current setting is 100A i am clipping at 50A. I should be able to get over 80A daily at this time of year with my 6kW solar
2. Charge current before float is 10A or 30% x C24. You can see current reduces to 5% x C24 by late float. Absorption setting is 5 hours but MPPT moves on to float after 1.5hrs!
3. Might the Multiplus be over ruling the MPPT?
Once again thankyou for your help in setting up my expensive off grid setup
Clive
Hi Clive,
Can you confirm exactly which model or capacity of batteries you have? As there are a heap of different sizes on the data sheet you attached. Also, is there a page with the recommended charge curve?
I think you have miscalculated the charge current %, but once you confirm which batteries you are using I can work it out.
There seems to be nothing wrong with the MPPT charge current into the battery peaking at ~50A (on the day shown). The MPPT can only charge with the max available solar power while in 'bulk' phase, which is until the absorption voltage is reached. Once in 'absorption' phase it needs to reduce the charge current in order to maintain the absorption voltage set-point, otherwise the battery voltage would keep on rising (destroying the batteries).
Of course during the peak of the day you will have more solar power available if you needed it (possibly enough to charge with the full 100A), but on the day shown the batteries are nearly fully recharged by mid-morning, so there is no opportunity to use it.
Unless you a running an ESS grid connected system, the MPPT & Multiplus chargers act independently.
With the MPPT, it uses an 'adaptive' absorption time (not fixed) - where the maximum absorption time set is multiplied by a factor determined from the battery voltage in the morning when the MPPT 'wakes up' and starts charging. That way the absorption time is varied according to how deeply the battery is discharged overnight.
You can read more about it here;
https://www.victronenergy.com/live/victronconnect:mppt-solarchargers
So the main thing you need to confirm is the charge current just before the switch to float over few days and what % of battery capacity it is. If its not <2% then it might be a good idea to increase the maximum absorption time.
