Imposible to make SOC lower with ESS

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Carrara Frederic asked Dec 10, '18

Imposible to make SOC lower with ESS

Hello dear team ! I've an installation at home with MutiPlus 48/5000, Fronius Primo on AC Out, Color Control GX, Ve.Bus BMS and Battery Lithium CB 300AH Victron.
The system is functionning with the ESS Mode and with not BatteryLife.
All is functionnig good but impossible to go down of 60% SOC and 51V approximatively even if i put 20% of discharge max on VEGX / ESS/ Max Discharge.
All firmware are the last. And in programmation i make the ESS standard options with lithium Battery Victron.
Can you help me ? Do you have a programmation more advanced than could use ?
Best regards

MultiPlus Quattro Inverter Charger Lithium Battery BMS CCGX Color Control Fronius

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Answer 1 · 2018-12-17T21:03:04Z

Guy Stewart (Victron Community Manager) answered · Dec 17, 2018 at 09:03 PM

Try checking the sustain voltage settings and Dynamic Cut-off settings in the ESS assistant on the Multi, configurable with VEConfigure.

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k2aab commented · Dec 20, 2018 at 10:33 PM

Hi Guy, I have a similar issue with a MultiPlus 2 and a LG Chem 6.5, my system stops when the battery capacity is about 40% today it was 47% remaining even though the active SOC is 15%. I've read the doc and for Lithium it says set the sustain voltage at 12.5 however this doc

https://www.victronenergy.com/live/doku.php?id=battery_compatibility%3Alg_chem_resu&do=export_pdf

For ESS and LG Chem says set the sustain voltage at 50V. I can't check the actual figure set in the system until i purchase a MK3 USB converter but the two values seem very different?

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Guy Stewart (Victron Community Manager) ♦♦ k2aab commented · Dec 29, 2018 at 08:59 PM

You can use Remote VEConfigure if you do not have a MK3USB.

https://www.victronenergy.com/live/vrm_portal:remote-veconfigure

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Answer 2 · 2018-12-18T05:46:56Z

Margreet Leeftink (Victron Energy Staff) answered · Dec 18, 2018 at 05:46 AM

It could indeed be that the sustain voltage is set too high.

Furthermore:

Are the battery monitor settings in VE configure made correctly?
Have you enabled Battery life on the CCGX? And what is the CCGX value of the “Minimum discharge SoC” setting.
Also a way to test is to disconnect AC in (simulate a grid a failure) load the system and see if the SOC will drop below 60%

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Answer 3 · 2018-12-27T11:18:30Z

k2aab answered · Dec 27, 2018 at 11:18 AM

Hi @Carrara Frederic I have the same problem, my sustain voltage is set correctly (50.0) as per Victron pdf, however i think this issue may be down to the Dynamic cut-off values in the ESS assistant. To me it suggests the more current you pull from the battery, the lower the voltage and thus the capacity is allowed to drop before the dynamic cut off cuts in.

So if you are only pulling a small amount of power the cut off value is higher (higher than the sustain voltage).Over the last few days (Christmas period) i have been doing a lot of cooking thus draining the battery at a large current, I've seen the battery capacity get down to 34%, the lowest so far.

What do you think?

I've also noticed there is a new ESS Assistant so will get that loaded as soon as i find time, this is where mine cut off today, still have 37% capacity left, even though my min active SOC is 15%.

I've also just updated the ESS Assistant so will see if that makes any difference tomorrow.

cut-off.jpg (23.2 KiB)

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Answer 4 · 2019-01-07T05:10:06Z

I have had very similar issues. Everything has been OK previously but over the holiday period the house had a large power/current draw from a heatpump and cooking etc.

I have ESS optimised for batterylife and 48v Lithium battery bank and found that the Quattro would draw all of the power from the grid, even when the battery bank was at >70% SOC and 51.25 v. Solar PV power was also being used but only around 500w.

Worse still, we had bad weather and when the grid went out: (1) the system did not switch over to power critical loads (like lighting and fridge freezer) from the batteries and (2) when the grid came back on the Quattro remained in "Off" mode (preventing any AC power to the house). I needed to do a hard reset from pulling fuses and disconnecting the data cables on the VE Bus BMS to get the Quattro to start again. (I see this same problem in another recent user post: https://community.victronenergy.com/questions/1867/quattro-stuck-in-off-status-and-will-not-start.html)

Can I ask Victron staff for any ideas?

I understand that if the BMS is reporting a low voltage alarm the Quattro switches to charger only mode and that if the grid subsequently goes down the Quattro then automatically switches to "off". But I can't find any explanation as to why the Quattro wouldn't start again when the grid is restored. Surely the Quattro should start up automatically and start charging the battery to remove the low voltage alarm?

I believe the sustain voltage setting (I'm running a 48v system) must be set at 50v (4 x 12.5v) as a minimum. I will need to check what figure is set on my system but as I said the system was often cutting off battery usage even when batteries were showing a high SOC and over 51v.

Would this be due to the Dynamic Cut Off algorithm kicking in at a higher than specified voltage due to earlier high current draw? Or possibly a bad cell in one of the batteries?

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