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evertlodder avatar image
evertlodder asked

ESS, Quattro + 2xMPPT 250/100 + lead acid battery bank - erratic behaviour

Hello! We have a situation of an unreliable grid with an essential load that requires backup.

We have installed a grid-connected backup system with solar array consisting of 1 x 10 kW Quattro, 1 x MPPT 250/100, 6 kWp solar array , Trojan 375 Ah @ 48VDC lead acid battery bank and CCGX. We have configured ESS and allowing feedback into the grid, set in mode "Optimized (with batterylife)" and "minimum SOC 100% (unless grid fails)". Battery monitor set to Quattro. Has no DC system. DVCC off. All loaded with latest FW.

The system is performing nicely most of the time, but about half the time they system restricts the solar yield to 0W and indicating on the display "ESS #1 #2" messages. Sometimes it actually cycles from restraining the solar for 100% , then allowing solar to generate, cranking up the solar, the ESS #1 #2 messages disappear and then the message appears again and solar is forced to zero W again.

The inverter works fine in case of grid failure, but it actually seems erratic behavior of the solar controller.



In the below graph, solar is suddenly restrained while there is plenty of sun. The battery bank remains at 100% SOC. The system does not regenerate any error messages, except the status message "ESS #1 #2" on the CCGX display.

I have a sense that there is a conflict between the inverter/charger battery charging protocol and the solar charging protocol, although the battery monitor has been set to "Quattro" (so the controllers are listening to CCGX, dictated by the Quattro, how I understand it). The reason I think there may be a conflict is the following: the battery voltage during daytime (solar power is available) is stable at 55V float voltage, while at night the battery voltage fluctuates between 50.5 V and 55 V.


Q: What can cause the issue that the solar controller is constrained in producing power to feedback into the grid? What is causing the battery voltage to fluctuate in the night (controllers off) and in daytime it is constant? And what is allowing the solar about half the time to work without any issue? We are happy to share the VEconfig file in case required.

Thank you in advance for your insight!

ESS
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2 Answers
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @evertlodder

Have you tried either:

-setting the SOC limit to 95%

or

-set ESS mode to 'keep batteries charged'

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evertlodder avatar image evertlodder commented ·

Dear Daniël,

Thank you for your quick reply.

We have tried both settings some time ago, Let me repeat and change the settings again and register carefully the behavior and feedback to you. May take little time, as I can only change the config when the essential load is off.

Thanks, Evert

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evertlodder avatar image evertlodder commented ·

Dear Daniël,


(1) Changed to "Keep battery charged". What happened before seems to be happening again and that is that the batteries show to be discharged. However, the sum of power in the system does not add up anymore. There seems to be a measuring/calculation mistake in the system.


The batteries are in reality not discharged. We tried this setting "keep charged" before and we experienced the SOC dropping over time. However, the battery voltage remains the same so in reality, the batteries remain charged. See graph below where we changed the setting to "keep charged" between 1-4 September.

After we realized this we changed the setting again to "Keep batteries charged" and the SOC recovered to 100% again (following what is should be, given the battery voltage).

(2) Keeping the status to "Optimized" and changing SOC to 95%, then the system restrains the solar output again (around 7:30am, but with solar available):

(3) putting it all back to how it was (optimized, SOC at 100%), then the situation does not improve. Solar constrained again, see graph below. Our experience says that solar might be allowed at some point of time in the day, but that seems completely random.

By the way, I changed the setting also to "disallow" feedback into the grid, but this does not change the last scenario. Still constraining solar.

Puzzled?

Best, Evert

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evertlodder avatar image
evertlodder answered ·

Dear Daniël,

Thank you for your quick reply.

We have tried both settings some time ago, Let me repeat and change the settings again and register carefully the behaviour and feedback to you. May take little time, as I can only change the config when the essential load is off.

Thanks, Evert


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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Hi @evertlodder

Normally you can change ESS mode without effecting any load, is there something in the system that influences this here?

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