question

benniej avatar image
benniej asked

Grid setpoint

Hi

I have read the 3 liner explanation on the link below at:

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

My questions are as follows:

1) Does this setting have any effect on how a system functions? Reading the above and posts it certainly does. Placing it under Settings -> ESS -> Debug causes some confusion for me. Has this been placed here for convenience while monitoring the values?

2) Does anybody have an example of how the "grid setpoint" should be calculated? i.e. Use System Overview - DC System - DC System (W) on VRM portal to determine the max value and set it to that.


Background on why I am asking the above questions:


I noticed that my battery gets discharged and charged multiple time per day. i.e. < 1% DOD. I am concerned that this is currently causing hundreds of cycles per day and would eventually ruin the batteries. Although the values on the pictures seem small they are more significant at other times during the day.


Charging:



Discharging:



I have set my system to:

System -> DVCC = Enabled (Was not feeding in when not enabled)

System -> Has DC system = Enabled

ESS -> Mode = Keep batteries charged.

ESS -> Feed-in excess solarcharger power = Enabled

ESS -> Debug -> Grid setpoint = 50W


Equipment:

1 X Qauttro 5KVA 48V (FW: 2658433)

1 X SmartSolar 150/70 (FW: v1.37)

1 X BMV 712 (FW: v4.01)

1 X CCGX (FW: v2.23 was doing it on v2.22 as well)

4 X Lead Acid 12V batteries connected in series.


Is the above caused by a feedback delay and sudden change in PV power produced or is something misconfigured? Any help / comments / suggestion would be appreciated.

Kind regards.

Bennie

ESS
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2 Answers
murph avatar image
murph answered ·
I noticed that my battery gets discharged and charged multiple time per day. i.e. < 1% DOD. I am concerned that this is currently causing hundreds of cycles per day and would eventually ruin the batteries.

I don't have an answer regarding the setpoint, but what you describe are not really cycles in terms of the advertised cycle life. Very small usage like that does not have a major impact on battery cycle life. With lead acid cells, small usage at the top of their capacity has negligible impact. It would take hundreds, possibly thousands, of top-1% mini-cycles to have the same impact as a single 50% cycle.

So, I'm not saying there is nothing to solve or improve, only that using the top 1% is not going to take much off your batteries long term health.

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benniej avatar image benniej commented ·

Hi Murph,


Thnx. That puts at ease a bit....

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boekel avatar image
boekel answered ·

This is normal behavior in ESS systems.
What kind of batteries do you have? normally 4x 12V batteries are not really suited for ESS systems.

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benniej avatar image benniej commented ·

Hi Boekel,

I have 4 X 12V Lead Acid 240Ah batteries. What type of battery should you use?

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boekel avatar image boekel ♦ benniej commented ·

Preferably lithium batteries.

2v lead-acid cells are also usable, a lead acid battery usually you should size at about 10x the maximum expected continuous (dis)charge rate.

In an ESS system you expect to have 1 cycle per day, your 4x 240Ah batteries won't last a year.

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