question

gat avatar image
gat asked

Should a/c coupled charge a battery in ESS mode?

Easysolar II GX not charging from a/c coupled PV. How can stop it exporting to the grid and make it go to the charger. Setup is ESS optimised with battery life using Pylontech US2000 and a current transformer on the incoming grid.


battery chargingAC PV Coupling
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Alexandra avatar image Alexandra ♦ commented ·

@Gat

I don't see your AC PV on the ccgx screen. How is it being monitored or was programmed into the system?

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2 Answers
gat avatar image
gat answered ·

The A/C coupled PV is connected to the AC 1 output and displays in the AC loads. The grid power is measured by a current transformer (CTR110000500 ).

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Alexandra avatar image Alexandra ♦ commented ·

Try limiting grid feedback or maybe prevent grid feed in for a bit until you are happy with battery SOC. See if it will charge up from the ac pv

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gat avatar image gat Alexandra ♦ commented ·

Turned of ac coupled feedback excess but it had no affect in passthru. It only comes out of passthrough when the batteries are fully charged. It is in ESS optimised mode and not batterysave.

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Alexandra avatar image Alexandra ♦ gat commented ·

It seems to be treating the pv like the grid basically then.

On ess with dc coupled pv the loads are fed from the grid in passthrough until they are charged or you have reached the desired SOC.

Does it still feedback even though you have turned off the feed in pv feature?

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gat avatar image gat Alexandra ♦ commented ·

Yes, the inverter is switched off until the batteries are fully charged and ac coupled feedback flows. Any dc coupled goes to the batteries. Once the batteries are charged it changes to absorption/discharge/bulk, the inverter now works normally and will use the batteries to discharge when there is a demand. Once there is no solar it switches to passthru and does not react to a scheduled charge window or any demand. It is more like what I would expect from a keep batteries charged configuration but it is set to ESS optimise.

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Alexandra avatar image Alexandra ♦ gat commented ·

By inverter is switched off, does this mean you are switching the inverter between charge and on? The inverter will switch to passthrough in charge mode.

If you just leave the victron inverter on, what happens when you want to charge with the ac pv?

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gat avatar image gat Alexandra ♦ commented ·

When say the inverter is switched off I mean that some relay must be automatically switching off the bridge (inverter) between ac and dc. I do not mean actually changing the physical switch on/charge.

If I set the scheduled charge on it will display the mode change but the charger will not charge from the grid. See below. As you can see I am losing 328W to the grid that could be charging the batteries.

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Alexandra avatar image Alexandra ♦ gat commented ·

Ok and if you disconnect the grid does it then charge the batteries?

Also what ac pv inverter do you have?

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gat avatar image gat Alexandra ♦ commented ·

If I disconnect the grid it does charge the batteries from both ac and dc coupled.

The inverter is SMA and does shutdown with a shift in ac frequency. It does not communicate directly with the Victron.

See below to show the third working state when the batteries are nearly charged. showing that the inverter can work. This is the state I would like it to stay in.

Also here is my veconfig details. I cannot see anything wrong.


TAB: General

System frequency 50Hz

Shore current 20.0 A

Overruled by remote checked

Dynamic current limiter unchecked

External current sensor connected (see manual) checked

State of charge when Bulk finished 85.0 %

Battery capacity 100 Ah

Charge efficiency 0.96

TAB: Grid

Country / grid code standard UK: G98/1 March 2019, G99/1 May 2018

LOM detection AC input 1 Type B (grid code compliant)

start P(f) at 50.40 Hz

start delay for p(F) 0.08 s

Droop for p(F) 10.0 %

Use Aux1 (if available) as disable FeedIn signal checked

Reactive power regulation Use a fixed Cos Phi

Filter time for reactive power 3.3 s

Cos phi at point 1 1.00

TAB: Inverter

PowerAssist unchecked

Inverter output voltage 230 V

Inverter DC shut-down voltage 44.00 V

Inverter DC restart voltage 48.00 V

Low DC alarm level 48.00 V

Do not restart after short-circuit (VDE 2510-2 safety) unchecked

enable AES unchecked

TAB: Charger

Enable charger checked

Weak AC input unchecked

Stop after excessive bulk unchecked

Lithium batteries checked

Use equalization (tubular plate traction battery curve) unchecked

Charge curve Fixed

Absorption voltage 52.00 V

Float voltage 51.00 V

Charge current 35 A

Repeated absorption time 1.00 Hr

Repeated absorption interval 7.00 Days

Absorption time 1 Hr

TAB: Virtual switch

TAB: Usage

Virtual switch usage Do not use VS

TAB: Assistants

TAB: Assistant Configuration

ESS (Energy Storage System) (size:1709)

*) System uses LiFePo4 with other type BMS

(This can be either a BMS connected via CAN bus or a BMS system in which the

batteries are protected from high/low cell voltages by external equipment.)

*) The battery capacity of the system is 100 Ah.

*) Sustain voltage 48.00 V.

*) Cut off voltage for a discharge current of:

0.005 C= 46.00 V

0.25 C= 46.00 V

0.7 C= 46.00 V

2 C= 46.00 V

*) Inverting is allowed again when voltage rises 1.20 V above cut-off(0).

*) The solar converter will start reducing its output power at 50.20 Hz.

Output power will be reduced to minimum when the frequency is 52.70 Hz.

The converter will disconnect when the frequency is higher than 53.00 Hz.

*) Total installed PV inverter power is 1500 Watts.

Total installed PV panel power is 1500 Watts.

*) Relevant VEConfigure settings:

- Battery capacity 100 Ah.

- PowerAssist unchecked

- Lithium batteries checked

- Dynamic current limiter unchecked

- Storage mode unchecked

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Alexandra avatar image Alexandra ♦ gat commented ·

https://www.victronenergy.com/live/ccgx:ccgx_sma

Does the GX register the SMA at all?

I know it does not control the sma at all and you have programmed it into the ess assistant.


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gat avatar image gat Alexandra ♦ commented ·

The GX does not control or register the SMA all it just sees a reduced demand on ac1 due to the PV. When there is excess PV on ac1 then this is exported.

The ESS assistant has been configured for 1500W of ac and dc coupled but I think this is just used for the 1:1 rule.

An answer could be if there is a way to activate the bi directional inverter via software?

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Alexandra avatar image Alexandra ♦ gat commented ·

Of you try get it registered using the link on my previous reply you may have more joy with the system. It needs to read the production I would think to know what direction to send it.

As you have it now it is behaving as system does with no ac pv attached.

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gat avatar image gat Alexandra ♦ commented ·

Thanks, I did not think of that. So it looks like my misunderstanding may be, that I thought in ESS it would detect flow outwards to the grid and redirect to charge. This would then have met grid set point condition. I do know that the inverter is about 10yrs old (SB1700) and does not have any ethernet only bluetooth. Perhaps there is another way to measure this? It looks like it would of been so much easier with a fronius.

Although It does not explain why a scheduled charge shows on the display, again no flow goes to charge the battery. As in the graphic shown above about a day ago.

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Gat

the system is in passthru, please read the manual about that:

(see Q4)

https://www.victronenergy.com/live/ess:design-installation-manual#faq

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gat avatar image gat commented ·

Yes, I have looked at Q4 and none of them apply. Any other sugestions?

Q4

1. Grid meter not enabled.

2. Battery information is displayed.

3/4.CCL=50, DCL=50 SOC quite high, Ac current limit not exceeded.

5. UK grid code, No aux.

6. Grid to inverter <2m.


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gat avatar image gat gat commented ·

Have now tested with AUX and LOM disabled. No change. I have now reset them back to default settings.

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gat avatar image gat gat commented ·

If the passthru caused by one o the items in Q4 would it still be able to go into the abosrption mode and pass dc coupled pv to the grid? when my Easysolar II gets to about 98/99% soc it comes out of passthru and into absorption/discharge/bulk mode. It then allows a flow through the inverter.

Then a few minutes later.

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