Will EasySolar II 48/5000 accept 3.7 kW of PV on AC-Out?

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sharpener asked Apr 5, '22

Will EasySolar II 48/5000 accept 3.7 kW of PV on AC-Out?

I have 2 x 2kW Steca AC inverters with 3.68kW of solar panels.

I plan to add an EasySolar II 48/5000, with another 3 to 4 kW of panels connected to its MPPT and 2 x 4 kWh of BYD LiFePO4 batteries.

I would like all the solar PV to keep generating during a power cut, so to do this I need to connect the Steca inverters to AC Out on the EasySolar.

Will the EasySolar shut them off if necessary by increasing the frequency? The inverters are UK G83 compliant and will trip if the frequency is >51.0 Hz for 0.5 secs.

In this situation the batteries will accept 130 A continuously and 180 A for up to 10 secs so should then cope with the full 70A output of the EasySolar charger.

Is this configuration OK and what do I have to do to set it up correctly?

TIA

EasySolar All-in-One

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marekp answered · Apr 05, 2022 at 04:27 PM

@sharpener

Thanks for yr quick reply @marekp. I was planning on using ESS anyway and I now see that frequency control is provided if you set it up with PV on the AC Out? = Yes.

Yes

I am a bit confused by the reference to Fronius, AIUI they have 0 - 100% modulating control designed to achieve perfect No Feed In. Whereas the Steca inverters are all-or-nothing so will generate at full power until the frequency is shifted to >51 Hz and then shut down, this will be fine provided the EasySolar can cope OK, I do not care if there is Feed-in or not (my UK FIT payment is mostly on generation not export).

The default FQ settings in ESS assistant are for Fronius.

If you know how your inverter is reacting to FQ changes, you can input your values.

EasySolar will not have a problem with inverter reacting like ON/OFF to FQ changes.

Before I got my Fronius I had inverter like that and there was no problem for EasySolar.

Related to all this is also the size of battery. Here it explains the Factor 1.0 rule: https://www.victronenergy.com/live/ac_coupling:start, this test is met. But later it says that you must have 4.8kWh of lithium batteries for every 1.5 kW of PV. This would mean I need 3 x 4 kWh BYD LVS (not 2) which means extra cost and space. Since the charge/discharge current is <60% of the maximum the batteries can take, can you explain the reason for this rule?

Suggested minimum battery size is related to the PV system working OFF-grid. Battery needs to be big enough to safely take the charging current from PV.

I think that 1.5kW/4.8kWh is bit too much. In my system I have 1.5kW/3kWh and it works quite well.

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Answer 1 · 2022-04-05T12:24:47Z

marekp answered · Apr 05, 2022 at 12:24 PM

@sharpener

It will work but you will have to load ESS or PV inverter assistant in order for PV inverter frequency control to work.

As a standard frequency settings are for Fronius but they can be changed to match you Steca inverter.

Here are my ESS settings.

l1-m-ess.jpg (150.6 KiB)

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Answer 2 · 2022-04-05T15:30:06Z

sharpener answered · Apr 05, 2022 at 03:30 PM

Thanks for yr quick reply @marekp. I was planning on using ESS anyway and I now see that frequency control is provided if you set it up with PV on the AC Out? = Yes.

I am a bit confused by the reference to Fronius, AIUI they have 0 - 100% modulating control designed to achieve perfect No Feed In. Whereas the Steca inverters are all-or-nothing so will generate at full power until the frequency is shifted to >51 Hz and then shut down, this will be fine provided the EasySolar can cope OK, I do not care if there is Feed-in or not (my UK FIT payment is mostly on generation not export).

Related to all this is also the size of battery. Here it explains the Factor 1.0 rule: https://www.victronenergy.com/live/ac_coupling:start, this test is met. But later it says that you must have 4.8kWh of lithium batteries for every 1.5 kW of PV. This would mean I need 3 x 4 kWh BYD LVS (not 2) which means extra cost and space. Since the charge/discharge current is <60% of the maximum the batteries can take, can you explain the reason for this rule?

TIA

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Answer 3 · 2022-04-05T17:21:16Z

sharpener answered · Apr 05, 2022 at 05:21 PM

Thank you, that is all very reassuring.

I was a bit worried that the 1.5kW/4.8kWh is a requirement for the warranty of either the battery or the EasySolar, but the charge/discharge current limit is fine and your experience seems to suggest the rule is unnecessary. The BYD size chart says a minimum of 1 x 4kWh is sufficient for the ES 5000 except (as you say) for off-grid use where you need 3.

Perhaps I will try and install the batteries so I can add an extra one on top if I need to!

Many thanks

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marekp commented · Apr 05, 2022 at 05:36 PM

@sharpener

No problem.

In any case you have to be careful with the charge current not to go over the top limit.

You are also planning to add MPPT charger with 4kWp so not only PV inverter will be the charging source.

To save the batteries I would go even lover than the max.

I limit the charging current in DVCC settings to 100A even if my batteries can take 200A as per battery maker.

I

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screen-shot-2022-04-05-at-73118-pm.png (26.8 KiB)

Answer 4 · 2022-04-06T10:39:27Z

sharpener answered · Apr 06, 2022 at 10:39 AM

Good point @MarekP. If I understand your reply correctly I had overlooked the fact that the the charger 70A limit does not include the MPPT output. This might be another 80A if I succeed in getting 4kW of extra panels on my roof (space is limited and there is some shading).

So (unless I add the third battery) your advice to limit the total charging current to less than the maximum allowed by the BMS sounds very wise.

Presumably if the grid fails the ES will shut down the MPPT first, and only trip the Steca inverters if there is still too much solar power? I haven't yet found any details of this anywhere.

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Answer 5 · 2022-04-06T11:30:45Z

marekp answered · Apr 06, 2022 at 11:30 AM

@sharpener

If I understand your reply correctly I had overlooked the fact that the the charger 70A limit does not include the MPPT output. This might be another 80A if I succeed in getting 4kW of extra panels on my roof (space is limited and there is some shading).

Yes, the 70A charging current is only from ES-II charger from AC side. The included in ES-II MPPT 250/100 can provide up to 100A charging current, on the DC side, directly to the battery.

So (unless I add the third battery) your advice to limit the total charging current to less than the maximum allowed by the BMS sounds very wise.

Even wiser is to limit charge current below the "max" allowed by BYD. The battery will thank you for it with longer service.

Presumably if the grid fails the ES will shut down the MPPT first, and only trip the Steca inverters if there is still too much solar power? I haven't yet found any details of this anywhere.

When grid is down and PV production can be fully consumed by house loads and battery, frequency of AC-out is not increased. (FQ value you can see in the "critical load" box at it's bottom)

When grid is down and PV production is higher than house loads and battery "save intake", ESS will first limit the production of the MPPT charger.

If this is not enough it will increase the AC-out frequency to lower the production of the AC-coupled PV inverter.

Here you can see how this frequency shifting works. (on top there is a missing input FQ when grid failed.

Here you can see that there is no FQ shifting if PV production is low.

In my system AC-coupled Fronius has 10kWp in panels and MPPT has 6kWp.

screen-shot-2022-04-02-at-101112-am.png (120.4 KiB)

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marekp commented · Apr 08, 2022 at 11:41 AM

@sharpener

I looked again at the MP-II behavior and noticed that power adjustments are happening at the same time at AC-out and MPPT.

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screen-shot-2022-04-08-at-13647-pm.png (122.9 KiB)

Answer 6 · 2022-04-09T12:30:27Z

sharpener answered · Apr 09, 2022 at 12:30 PM

Thank you, that looks fine.

But I am puzzled by the previous illustration, the total consumption is 4121W and the total solar is 4102, a deficit of 19W. But the inverter is shown as charging at 2547W, where is this coming from and why if there is no AC input?

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marekp commented · Apr 09, 2022 at 12:33 PM

@sharpener

The numbers are calculated and when situation is dynamic they not always make sens. :)

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