question

Tom Ranson avatar image
Tom Ranson asked

ESS going into Sustain too soon

Hi all,

Grid parallel ESS

Cerbo GX with ESS with DVCC

MultiPlus ii

SmartShunt

2x MPPT 100/30

24V battery bank (8x 6V FLA in series/parallel)


My ESS is going into Sustain far too early, when the batteries are only at c. 90% SoC. I have it configured as Optimised with Battery Life.

I believe that the reason for this is the values configured for the Dynamic Cut Off, however I am using the ESS default values for Gel/AGM batteries, as I believe this is the closest battery type to my FLA. I am seeing the system enter sustain mode at 23.99V, and therefore my batteries are not discharging significantly (minimum SoC set to 50%). I believe I should be able to take the batteries down to 23.00V without any issue or risk of damage.

Could anyone guide me further on this or help me optimise my settings please? I'm not sure that my dynamic cut off values are appropriate for FLA batteries, but can't find any documentation or guidance on this anywhere.

ESSbattery
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3 Answers
gfillary avatar image
gfillary answered ·

Im having the same issue. I'm running a 48v system with a multiplus II with 8 x 170Ah power safe batteries after starting with 100% fully charged, it goes into idle mode after on 4.5Kwh has been drawn. However my smart shunt is still saying I have 50.20v's

Im missing as setting somewhere....

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nickdb avatar image
nickdb answered ·

People, SOC is a derived metric. If the measuring instrument is flawed or setup incorrectly then it is meaningless. Voltage is king. You can only hit sustain if you have setup ESS wrong or the voltage dropped long enough. Read the manuals, setup your systems properly and it will all work out. These are bleak posts that just suggest you need a professional to help.

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Alexandra avatar image Alexandra ♦ commented ·

@Tom Ranson

@gfillary

https://www.victronenergy.com/media/pg/Energy_Storage_System/en/controlling-depth-of-discharge.html#UUID-6b8f380a-3e19-c040-9dad-673577d775d5

Lower your dynamic cut offs, default does not work for everything.

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Tom Ranson avatar image Tom Ranson Alexandra ♦ commented ·
Hi @Alexandra thank you. Yes, I have read and re-read the documentation and still can't fathom what the correct and safe dynamic cut-off values would be in my situation with FLA batteries. There is no help in the documentation for this battery scenario, and as far as I can tell, no useful information on the forums.


If you could assist me with understand what would be appropriate values in my specific use case, I would much appreciate it please.

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Alexandra avatar image Alexandra ♦ Tom Ranson commented ·

@Tom Ranson

It is hard to say, as they are also affected by age, bank size, battery manufacturer recommendations.

For the most part as long as they are not below your low DC cut off, you will be fine. Even setting them all the same to eliminate that setting as the problem.

You can still program your inverterter to shut off at a certain SOC (depends on how you want to use them). FLA does have quite a voltage collapse under higher load.

All I can say is you need to experiment. Use the VRM or GX to see where the voltage drops under each c rating load and set it from there.

The discharge curve graph information from the battery manufacturer will help as well as it usually shows how the battery acts or is supposed to act under different loads.

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Tom Ranson avatar image Tom Ranson commented ·
Hi @nickdb thank you for your response. I totally agree and understand that SoC is only a calculated metric, however I am still struggling to know what is the best practice for the dynamic cut off values when using FLA batteries (as there is no corresponding battery type default in ESS), which isn't documented or as far as I can find, discussed on these forums.
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hereandthere avatar image
hereandthere answered ·

@Tom Ranson I'm experiencing similar issues. My system is with 4 200Ah lead-carbon batteries in series on a easy solar gx with smart shunt.

Did you find the right settings for your system to work properly?

Is it really that simple to just alter the cut-off settings?


O and one more thing, I'm trying to do a full charge every day (when the price is low) but set the ess at green doesn't charge to 100% for some reason I can't figure out.

A pink bar (grid to battery) does appear, and as the time passes the pink bar moves in time and keeps moving up to the evening when the price is high again without any charging. And; there is this yellow notification on the dashboard: "battery balancing is scheduled for today" but it doesn't?! I am confused


Any tips would be appreciated


H


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