question

Paul avatar image
Paul asked

ESS needed for feeding in PV energy from Smartsolar when batteries are full?

Hi Victron professionals and enthusiasts,

In order to provide correct information to my question, my system consists of:
1 x MP2 5000/48 1 phase setup
Smartshunt
Carlo Gacazzi ethernet power meter EM24
1x Smartsolar 250/100
Cerbo
8 kWh LiFePO4 battery controlled by a CANbus communicating Batrium BMS.
12 + 5 x 365Wp AEG glass/glass panels on a SMA STP5.0
10x 365Wp AEG glass/glass panels, each connected at a Enphase IQ7+ on one phase.


Yesterday, I removed 10 pcs Enphase IQ7+ micro inverters from the panels and connected the panels in series over two separated strings of each 5 pcs 365Wp panels in parallel tot he Smartsolar 250/100 (5s2p)

So far so good and all works. Smartsolar shows up and is charging a little bit (no sun here at the moment).

My question is: since the power comes from the DC battery side now, will the Multiplus2 feed in the energy coming from the Smartsolar when batteries are full?
Or do I need to install the ESS assistant?

I want to operate as long as possible without the ESS because this ESS mode uses more power that a passive standby backup system and also wears the batteries unnecessary unitl feed-in is not paid anymore by the grid-operator.

ESS
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2 Answers
Alexandra avatar image
Alexandra answered ·

@Paul

No feed to grid with no ESS. It will feed loads.

Does it charge the batteries without ESS? yes.

If you want to prioritise solar for loads without ess, you will need to disconnect the grid. Or put the input current limit right down, which will pull a bit from grid all the time.

Not sure how ESS would use more power than a normal set up? I have run both on mine and have not noticed a difference. The components need what they need.

You dont have to cycle the batteries on an ESS system. There are settings to control that.

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Paul avatar image
Paul answered ·

@Alexandra proof is eating the pudding: I just monitored the behaviour of the MPPT250/100 and it nicely throttled when the battery is full, without sending power to the grid over the MP2.

I will install the ESS as soon as I have upgraded the system with two extra MP2 5000/48's.

Any idea what I should do?

a) keep using the Smartsolar 250/100 for one set of 10 panels (previous on 10 x IQ7+) in order to charge the batteries or connect a Fronius Symo at the AC out of the MP2 in order to raun with frequency shift control in case of net failure

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Alexandra avatar image Alexandra ♦ commented ·

@Paul

It is more efficient to use DC coupling for battery charging.

The fronius for loads direct.

The main reason being charging with the fronius is the number of steps in conversion. dc from panels to ac out from the fronius back down to dc again for the batteries. There are always losses (which means heat in the MP2s which then derate.)

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