question

Edgar Graadt van Roggen avatar image

How do I get SOC to show 100%?

Hi Community,

I have hesitated to put this question into the Victron Community blog until I have searched and read everything I could on the SOC topic.

I have installed a Multiplus II GX with 8 x 150 Ah AGM batteries (two parallel series of 4), 9 x 280 Wp panels (3 parallel series of 3) and an MPPT 150/60. There is no separate BMV battery monitor. Everything is working fine (VRM also), except for the SOC indicator.

I checked with the distributor of the batteries and have adjusted the absorption and float voltages in the Multiplus II GX and MPPT configurations.

Once connected to VRM, the SOC indicator showed 85%, even though from the voltage and current measures we have been in absorption and even float stages (also indicated by light indicator on MPPT). There is little consumption on the system, but the highest SOC level we have achieved in the last 7 days is 87%, even though at that point, the battery bank charge current has already dropped to 0,5 Amp.

From the voltage/current curves (from the widget), it seems to me that the batteries must have a higher SOC than indicated. Will the SOC indicator eventually jump to 100% once there is no charge current anymore flowing into the batteries? Do I just need to be more patient and the system will eventually adjust itself to 100%?



SOC
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

12 Answers
Edgar Graadt van Roggen avatar image
Edgar Graadt van Roggen answered ·

Hi Elimac,

Mi problem is fixed!!! Today after finishing bulk, the SOC jumped to 90% and then to 100%. Last night I increased slightly the difference in the absorption voltage set in the MPPT vs. the Multiplus. Originally My system is a 48 Volt system, and I had originally set the absorption voltage parameters as 56,6 Volt in the MPPT and 56,4 Volt in the Multiplus. Last night I lowered the absorption voltage in the Multiplus a bit more to 56 Volt, in order to increase the difference. I think this change finally triggered that the Multiplus recognized that the bulk stage in the morning hours had finished, as the SOC first jumped to 90% (as I set in the Multiplus in the setting "% SOC when bulk is finished"). During the absorption stage the SOC then jumped further to 100%.

The manual indicates that one needs to set the absorption voltage in the MPPT a bit higher than in the Multiplus, and I guess it is a matter of trial and error to see how big this difference needs to be in your system in order for the SOC algorithm to work correctly. The MPPT and Multiplus measure the voltages at their own cable connection points, not a the battery conector itself, and I guess because of voltage losses in the cabling, the voltages seen by the MPPT and the Multiplus will be slightly different (but always higher at the MPPT contact).

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Edgar Graadt van Roggen avatar image
Edgar Graadt van Roggen answered ·

Hi Elimac,

Thank you for your recommendation. I will try that.

Looking a my DC charge voltages and current graphs, I think I am on to something. And it is related to the adaptive absorption time algorithm.

From the DC graphs I see that my battery bank voltage never drops below 51 Volt at night. Under the adaptive absorption time algorithm, if the battery voltage at solar start-up is higher than 12,6 Volt (i.e. 50,4 Volt in a 48 Volt set-up like mine), then the maximum absorption time is reduced to 1 hour. And I see that that is exactly what is happening in my system.

When the system was installed and connected to VRM about a week ago, the SOC started at 85%, as this was the level set in the "% SOC when bulk finished" parameter in the Multiplus. Since the batteries where full and there has been little AC consumption, the voltage of the batteries has not dropped below 51 Volt and the adaptive absorption time algorithm has kept the absorption stage to 1 hour, and then switches to float.

I think that could be the reason why the SOC has slowly been dropping, as the absorption fase has been too short to raise the SOC (and float of course doesn't raise it either).

The only other thing I am still puzzled by is why the SOC has not returned to 85% automatically, every time the bulk stage finishes. It seems like the SOC algorithm is not doing an ´SOC reset¨ every time the absorption voltage is reached. I do have a higher absorption voltage set in the MPPT compared to the one set in the Multiplus (56,6 Volt vs. 56,4 Volt), but maybe the difference should be greater. I.e. maybe the Multiplus doesn't recognize that the absorption voltage has been reached and therefore does not do the "SOC reset" to 85%.

This reasoning sounds plausible?


3 comments
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

What firmware is the Multi running?

Hi John,

The Multi II GX is running on firmware version 456.

Here you can see that the SOC finally jumped to 100% today.

elimac avatar image
elimac answered ·

@Edgar Graadt van Roggen

Try setting the maximum absorption time in Multiplus as LESS when compared to what you usually have with the MPPT.

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Edgar Graadt van Roggen avatar image
Edgar Graadt van Roggen answered ·

JohnC,,

Thank you for your comments. yes, my battery bank capacity is set at 300 Ah in the Multi menu. regarding the V´s, I have set them according to the battery manufacturers specs. I got an email from the manufacturer, stating the specific V´s, so I have no doubts there. I have also set the V´s slightly higher in the MPPT vs. the Multiplus, something I read wrecommended in the manual.


From the various blogs, I see that many are having very similar issues as I am having regarding the SOC.


Next possible solutions I will try are:

a) lowering the parameter on charge efficiency, as you suggested (thank you);

b) raising the setting under "% charged when bulk is finished" from 85% to 90%, and see what happens then.


I am still puzzled by all this....Can´t seem to figure out what is causing the incorrect SOC reading. Since the system goes through a short bulk cycle each day and reaches the absorption voltage, the SOC reading should at least jump at that point to the level set under "% charged when bulk is finished", but it doesn't.





1 comment
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

There's mention of this in the CCGX manual..

"2.2.5 Details on VE.Bus SOC

  • While the Inverter/Charger is in bulk, the SOC will not rise above the value as set in VEConfigure3 for the “State of charge when Bulk finished“ parameter on the General tab; default 85%. In a system with Solar chargers, make sure that the Absorption voltage as configured in the MPPT is slightly above the same setting in the inverter/charger. The latter needs to recognize that the battery voltage has reached the absorption level. If it doesn’t, the SOC will be stuck at the earlier mentioned End-of-bulk percentage, default 85%."

Might this be your issue? I'm not sure why it says "stuck at", but I can see why it mightn't reset to the 85% unless the Multi senses V higher than it's own Absorb setting.




JohnC avatar image
JohnC answered ·

Hi Edgar. Some general observations..

1/ With 8x 150Ah batts configured 4S2P, you should have 300Ah set as your batt capacity. Have you?

2/ You have a short Absorb time because your batts are starting the day in good condition (probably better than 90 %). If you're using an Adaptive algorithm, that's to be expected, so all good there.

3/ In Float, the charge current 'tail' is quite low (<1% of batt capacity), so yes, they're effectively 100% charged when you see it taper down to constant A. You seem to have a small fluctuating load, like maybe a fridge, but doesn't matter.

3/ If your base 'tail' is just 1A, then it would take 3 hours to show a 1% SOC rise. If you have a Charge Efficiency setting available, you could lower that too, it will calculate a faster rise in SOC.

4/ Don't forget temp compensation when setting your V targets. Your mppt will do that for you unless turned off, so no need to adjust for it. Your batt maker/supplier should be aware too when recommending V's.

Maybe some of this can help..


2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Edgar Graadt van Roggen avatar image
Edgar Graadt van Roggen answered ·

Attached is an image of the MPPT voltage and current curve widget. One can see from these that every day there has been a very short bulk and absorption period, followed by the float stage (on Jan 19th I lowered the absorption voltage to 54 Volt from the preset of 55,2 Volt, based upon the feedback on this issue from the battery distributor). On the Multiplus settings (general tab), I have 85% set as the "SOC when bulk is finished". So the SOC should have always finished the day above 85%, but it hasn't. I guess there is still something in the setting or algorithm that doesn't recognize the right SOC.


1 comment
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Are you sure you selected the correct profile? I'm surprised to see the above... it seems a lithium charge profile, not AGM. Maybe I'm wrong, I was expecting a charge profile similar to lead acid. How much time are they staying in bulk and absorption? Maybe you are charging it in float, basically...??

If so, they may be undercharged. I think you should have lowered the voltage on Multiplus (reference), not on the MPPT.

Returning to your main question, you should obtain 100% when MPPT stays in absorption more time than what is set in the Multi. I thought your problem was the Multi having this value too high, but maybe is the other way around? Mppt absorption time too low ?

Edgar Graadt van Roggen avatar image
Edgar Graadt van Roggen answered ·

Hi Elimac,

Thank you very much for your suggestions. We don't have AC available yet, so I will try the other options you suggested. In a past post I saw the suggestion to slightly lower the absorption voltage in the Multiplus charger vs. the MPPT, and I did that already. The absorption voltage in the Multiplus is set at 56,4 Volt vs. 56,6 Volt in the MPPT charger. But that hasn't solved the issue. Maybe the difference should be greater.

I will therefore try your other suggestion, and shorten the absorption time in the Multiplus menu. I will let you know if ithat solves my issue. Would be great. Thanks again.

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

elimac avatar image
elimac answered ·

Hi,

I've stumbled on the same issue. As far as I could understand, you have at least two ways to make it 100%. The trick is that what controls this is what you have set in the Multiplus / VE Config in the Charger section.


a) If you have AC available, let the Multiplus charge the bank (at night for example) one time and reach the Float phase. It will reset to 100% SOC.


b) If you lower a little (100mV) the absorption voltage set in VEconfig/ Multiplus charger, it will help the system recognise absorption phase when power is provided by MPPT. And more importantly: lower a little (try to make it still sensible) the absorption time set in Charger setting in VEconfig. In my experience, once the total absorption time (provided by MPPTs) exceeds this time set in VEconfig, it also resets to 100% SOC.

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Edgar Graadt van Roggen avatar image
Edgar Graadt van Roggen answered ·

As additional information, the battery monitor in VRM is selected to be the Multiplus II GX.

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Edgar Graadt van Roggen avatar image
Edgar Graadt van Roggen answered ·

Here a screenshot from VRM. The system was connected to VRM on the 13th of January. The SOC started at 85% and its has reached a max of 87%, even though we have had plenty of solar generation in excess of consumption. I am just puzzled by this.


2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Edgar Graadt van Roggen avatar image
Edgar Graadt van Roggen answered ·

Hi M. Lange,

Yes, the MPPT is connected to the Multiplus II GX via a VE.direct cable, and the MPPT shows up as one of the connected devices on VRM.

1 comment
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Is the Multi selected as Battery monitor (and is the battery monitor activated in the Multi and is there set the correct battery capacity) and is "Use solar charger current to improve VE.Bus SOC" active?
https://www.victronenergy.com/live/ccgx:start#configurable_parameters

Are there any DC loads?

Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Is the MPPT connected to the Multiplus II GX via a VE.direct cable?
Only with this connection the GX device can count the current coming from the PV and use it to increase the SOC.

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.