Charge predictions being wrong

[larsh (Lars)]

I have 1 multiplus II 48v 8000VA. with a 5KW solar inverter. I have given the DESS the following parameters:
|Can you sell energy back to the grid?|Yes|
|Maximum import power|6.4 kW|
|Maximum export power|6.4 kW|
|Operating mode|Trade mode|

The problem is that it thinks it can charge the battery with 6,4kw from the grid + whatever the solar forecast is in this case about 3.4kw. It doesn’t take into account that the limiting factor for this prediction is the victron itself. It only takes into account the 6.4 kw of our grid connection.

|Battery capacity|43 kWh|
|Maximum discharge power|20 kW|
|Maximum charge power|20 kW|
|Estimated battery cycle life|8000|
|Battery price|€ 2400|
|Battery cycle costs per kWh|0.01 €/kWh|
|Battery balancing|On|
|Full charge interval|28 days|
|Do you want to restrict the battery usage?|No|

My battery can discharge at 20kw, but the inverter can not do more than 110A of charging and about 6400W on ac which translates to about 7200W on DC before losses. Should I then change these parameters?

I would have assumed the DESS Parameters take the Victron Inverter limitations into account, but they don’t seem to do so.

[grua]

@larsh

|Maximum discharge power|20 kW|
|Maximum charge power|20 kW|

You have to set these two parameters to the real possible power rates. DESS doesn’t take anything into account by itself.

[larsh (Lars)]

But then what values should i use, because you have before and after conversion losses. Here I convert about 6400W to Ac but it takes out about 6774W out of my battery. But when I charge my battery with the Multiplus It usually draws about 6000W to charge my battery with about 5200W

[grua]

In my experience, the AC side values fit better

[Sarowe1990]

Observe something and enter somewhat realistic values. You may be able to correct something later. The more realistic the values ​​are, the smoother the DESS runs

[vahur]

I’m not sure what you mean but do you expect the charge forecast on a sunny cheap hour to be 6,4kW + 3,4kW = 9,8kW?

Is it the same issue as here?

DESS Maximum charge power

Hello! I enabled DESS and its working fine. My setup is: 3 x Multiplus II 5000 in 3-phase operation 1 x MTTP RS 450/200 8 x Pylontech US5000 I have one problem with it: the system does not understand the Inverter limit. In the cheap pricing hours its needed to charge the batteries with maximum power. From both MPPT and grid. If I set the “Maximum charge power” to 12kW (3x4kW from inverter) then in the daytime it will take everything from MPPT (6kW for example) and 6kW from inverter. But …

[Sarowe1990]

There are several factors that limit your charging capacity, for example. For example, the settings regarding the maximum load of your house connection. Or settings in the battery or BMS. Or settings in the DVCS. For example, according to the data sheet of the MP2, my theoretical charging capacity is 6.2 kWh. In practice, the system charges around 5-5.5 kWh into the battery. In order to plan the schedules correctly, it is important to specify the maximum charging rate somewhere around 5.5 kWh and not the theoretical 6.2 kWh from the data sheet of the MP2. The same applies to the discharge rate.