Multiplus 3000 + ESS : no AC out when grid failure

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rodolphe-yonnesolaire asked Sep 26, '19

Multiplus 3000 + ESS : no AC out when grid failure

Hi, I tried ti find an answer to my problem reading 9 pages + grid failure filters but do not see wothming to help me.

My system is Multiplus 3000 + MPPT 150/45 + LG Resu 3.3 + CCGX + ESS . All software/firmware updated.

When there is a grid failure and IF my multiplus Inverter is running, I see the multiplus commutating immediatly to battery+solar mode to power on Ac out... Nice and no power vut in my house.

But if the grid failure comes when the Inverter is not running (pass-thru mode) AND the battery SOC is > to SOC min (even if SOC is min, I read that the SOC min is not follow for grid failure, correct ?), I get no more power on AC out , I mean the Multiplus is not running inverter and taking power from battery, even if I wait for several minutes... Should it no commute very fast to back up mode ?

Where is the problem ? Is there a Grid mode setting problem ? I'm in France and cannot use the French Grid mode because the multiplus has no internal ENS (VE config refuses this mode), so I tried with UK & German grid mode with LOM B, but same result = I turn OFF the grid on evening (no more solar) and no power goes from battery to my house...

Should I select the GRID "OTHER" mode ?

Many thanks for help or suggestions.

ESS

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Daniël Boekel (Victron Energy Staff) ♦♦ commented · Sep 27, 2019 at 06:12 AM

Hi @Rodolphe - YonneSolaire

What site is this? I can take a look if you want to.

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rodolphe-yonnesolaire commented · Sep 27, 2019 at 07:38 AM

Hello,

My site is YonneSolaire - Czuba

On VRM map it is in the 87 group

I can invit you with full access if you tell me an email. Don't know what you need to have a look...

Thanks

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Daniël Boekel (Victron Energy Staff) answered · Sep 27, 2019 at 08:02 AM

Hi @Rodolphe - YonneSolaire

I think I found the problem:

The Cut off voltages are incorrect, see:

https://www.victronenergy.com/live/battery_compatibility:lg_chem_resu

quote:
The dynamic cut-off values will effect the depth of discharge you will cycle the battery. The default settings are very safe and conservative, but not optimised for full consumption of battery potential.

If you wish to cycle the battery deeper, a flat dynamic cutoff value of 46V allows this system to discharge to the CCGX set SOC limit of 15%, and then a further self-discharge down to ~11% each night.

screenshot-2019-09-27-095832.png (40.5 KiB)

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rodolphe-yonnesolaire commented · Sep 27, 2019 at 09:07 AM

OK this is very interesting but maybe we have a misunderstanding...

My goal is not to deeper discharge my LG Resu under 20% SOC (as it is set actually) each days but just when I have a grid failure...My problem is to get power in the house if Grid falls when the inverter is off AND my battery has yet enough energy ( I mean SOC=20% as set and multi is in the 100% transfer mode)...

Ok, I will check my settings and do some tests and go back to you to give results.

Thank you very much for your very quick answers..This is great job.

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Daniël Boekel (Victron Energy Staff) ♦♦ rodolphe-yonnesolaire commented · Sep 27, 2019 at 10:32 AM

I understand you: your inverter cuts out at 52 volt when there is low load on the output, that's why you have to set all cutoff values at 46 volt in the ESS assistant.

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rodolphe-yonnesolaire commented · Sep 28, 2019 at 08:44 AM

I re-programmed this morning with Cut-off of 46V and it seems working fine now because with 35% SOC my inverter is running taking a very small current from solar. Great !

Thanks a lot and congratulations for your exact comment on my problem !

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Answer 1 · 2019-10-01T22:18:28Z

rodolphe-yonnesolaire answered · Oct 01, 2019 at 10:18 PM

Hello,

It seems this is not yet perfect with 46V. I mean the Cut-off arrives at SOC of 22%...

I checked the SOC evolution and the cut-off arrives each time at 22% with a Battery voltage around 50.7V... Then the SOC rises again, the inverter starts ON again.

What is the link between the 50.7V I see when cut of and the 46V I put on all four entries ?

Are not the 4 values to define a curve ? The default values are all 4 different (from 52 to 48V)... What may be the 4 good values to follow this same curve but lower with a 18% SOC Cut-Off ?

Can I try 45V by example...? How to compute the good value(s) ?

Thanks

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Daniël Boekel (Victron Energy Staff) ♦♦ commented · Oct 01, 2019 at 10:37 PM

Hi @Rodolphe - YonneSolaire

in the ESS menu you can set the SOC you want the system to discharge to under normal circumstances.

The rest of the battery capacity is reserved for backup power when the grid fails, if you have a stable grid, you can choose a low SOC in this setting, when you have a grid that fails more often, you probably want a high SOC setting to have more battery capacity left when there is a grid failure.

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Answer 2 · 2019-10-01T22:49:55Z

rodolphe-yonnesolaire answered · Oct 01, 2019 at 10:49 PM

Sure I know the setting of the SOC in the ESS Menu, and sure I may to set the SOC to 25% and my problem of cut-off at 22% is solved : the battery will discharge up to 25% and if I get a grid failure before 25%, the inverter is running and I get no grid cut off...

But if I want to have an inverter running up to 20% SOC ? Actually with 46V setting , the inverter cut-off when the SOC arrives to 22% (50.7V).... So my question is : can I gain 2 or 4 % of SOC by setting a Cut-off Voltage under 46V ?

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Daniël Boekel (Victron Energy Staff) ♦♦ commented · Oct 02, 2019 at 12:19 AM

at 46 volts, your battery is really empty, not 22%

It is a problem to run the LG chem too low, to the point where it’s BMS goes into protection mode. One of the issues with LG battery is that the BMS will trip a physical hardware switch, not a relay or FET. This requires a technician or very technical end user to physically prepare the system to restart, it will not recover on it’s own like using the recommended settings - so is NOT RECOMMENDED.

It is also possible to damage the battery in this low state if it is left and not quickly attended too and recharged. It is not worth it for a few extra % of battery capacity.

The sustain voltage threshold of 50V is set in the ESS assistant. The battery will continue to discharge to run the loads if the grid is disconnected, but will return to 50V as soon as it can.

This is a safe voltage for the LG, and you should be very careful going below it as you will be outside the specifications.

The LG battery is not intended for this kind of full cycle no-grid use, it is only for ESS where the grid is nearly always available.

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Answer 3 · 2019-10-02T21:35:52Z

rodolphe-yonnesolaire answered · Oct 02, 2019 at 09:35 PM

OK, so, why my inverter is cutting OFF when Battery Voltage is 50.7V (SOC 22% each time I saw)...?? I understand more than 50V is not 46 V... I set all values to 46V from 0.005C to 2C.

I'd like to understand...

I have very low load at night (100W)...and slowly the SOC is falling with Inverter running from battery + a part from grid (50W ) grid set point) = fine !

But at a moment and BEFORE my Minimum SOC (20%) is touched, the inverter cut-off.. (SOC 22%), and it is too soon...

Unfortunately if I get a grid failure with SOC at 21% , I will lost power on the house with the duration of the grid failure... I want my inverter running up to 20% SOC (and even 19% to have a sécurity marge), so like this, if I get a grid failure before or while 20% SOC, my inverter is runnng and so, there is a 30us switch from partial grid (50W) + battery to 100% battery and I get no power break at all in the house. Hope I'm clear with my english...

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