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smejfi avatar image
smejfi asked

ESS batery usage preference

Hello, Im running 3 phase ESS system with Multiplus II 3000/48 and one Victron MPPT 150/100. I would like to ask if it is somehow possible to force ESS to use as much solar as it is possible and take the rest of the required power from the grid instead of taking it from the battery? It seems quite anoying that when ESS #1 (and in case of batteryLife #2) occurs, ESS turns off the inverters, which prevents direct use of solar until the battery percentage rises a bit, instead of that I would sometimes prefer not to touch battery and use the rest of the required power from the grid. I guess that most of those issues would be solved by means of using grid tied MPPT like fronius, but that seems to be too much of an investment for me now. Any suggestions howe to solve this with my current setup? Thank you for your answers.

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seb71 answered ·

It only happens if your loads are greater than what your panels can produce at that time, so the battery has to supply the difference.

If you have ESS#1 (in case of using Optimized without BatteryLife), as soon as the battery is charged back by 3 SOC percent points above the minimum SOC you have set, the solar charger should power your loads again (using the battery if needed).

Similar for #1 and #2 (Optimized with BatteryLife), but in that case if minimum SOC is reached, the Active minimum SOC is raised by 5 percent points. So it needs need to charge 5 + 3 percent points.

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smejfi avatar image smejfi commented ·

Thank you for your answer, Im aware of all of that, the problem is that espetially in winter time the loads are greater than PV very often so I thought it would be better to leave the batery on some reasonable SOC (75-80%) and use only PV and grid...but it seems this is not possible so far (without using the hysteresis of those 3% on the battery and cycle it all the time)...

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seb71 avatar image seb71 smejfi commented ·

It is possible. But you will have short interruptions while the battery is charged back, as explained. And if you can't recharge by 3 percent points, then it means you have very little energy from the Sun anyway.


Why do you want to use the grid during the day? If you want to extract as much energy as possible from the Sun, you must use the batteries.

Usually the loads are not constant, so if you keep the batteries always charged, when your momentary loads are smaller than what your panels can produce at that time, you won't use that energy.

This is for the case in which you do not feed in energy into the grid (you did not said that you want to feed in into the grid).

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smejfi avatar image smejfi seb71 commented ·

Sorry, I didnt mention that, I DONT want to feed in to the grid (but on the other hand when this option is enabled, victron seems to be less "afraid" of using solar). The thing is that now in winter time my Pylontech batteries are often bellow 18°C, which prevents them from charging with the full power, so when the min SOC is reached, my MPPT is limited by the maximum allowed charging current, so until those 3 percent above min SOC are reached, Im using e.g. half a power of PV than it can actually produce. But truth is that it is only for a short time, so the loss is probably quite negligable...still it bothers me a little :-D

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seb71 avatar image seb71 smejfi commented ·

Set the minimum SOC much lower (and use Optimized without BatteryLife).

You bougth LiFePO4 batteries, but you are using them as if they were lead-acid batteries.

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smejfi avatar image smejfi seb71 commented ·

You mean that Im trying to save them too much? Or what do you mean by using them as lead-acid?

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seb71 avatar image seb71 smejfi commented ·

Lead-acid batteries will degrade and lose capacity if not fully charged frequently (preferably get them to 100% SOC every day).

Also lead-acid batteries will lose capacity if discharged too much (safest is to limit the discharge to 70% State of Charge / 30% Depth of Discharge).

Lead-acid batteries are also less energy efficient.

Lead-acid batteries also have lower usable total number of cycles.

They have lower charging and discharging currents.


You pay more for LiFePO4 to not deal with these lead-acid batteries drawbacks.

If then you use the LiFePO4 batteries as if they were lead-acid batteries, it is a waste of money. You might as well buy cheaper lead-acid batteries instead.

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