question

Jaco Reinecke avatar image
Jaco Reinecke asked

ESS suggestion for better battery use

Having used ESS for a while now coupled with previous experiences with non-Victron software to optimal use batteries, being from South Africa, please find 2 suggestions.


Under the ESS menu, call it say i.e. Battery Use, where one can:
1) Set the a max AC watts that can be drawn from the batteries during daytime, linked to the the existing SOC.
2) A schedule for evening use of batteries, with these options:
2.1) the max AC watt that can be drawn from the batteries
2.2) with a pre-set SOC above the SOC the system uses, before reverting back to utility power,
2.3) with a pre-set time to start recharging the batteries.

Re. 1: One can then set a optimal "slow" discharge of your batteries, XYZwatts AC max, with peak loads taken up by the Grid during the day instead of pulling the max the batteries can give.


Re. 2: Between 12am and 6am draw a max of XYZwatts AC from the batteries to a pre-set SOC of XYZ% and only start recharging the batteries from 10am only.

During power failures the above settings are obviously ignored.

The core idea behind the above is to give users the option to not over strain the batteries during short burst of power needed daytime and the option to select when to use the batteries for even more savings, managing the recharge if one uses this option, as one knows that between X and Y times there tends to be spare power ... as per the data one has accumulated.

Thank you for reading, hope this could be considered.
Regards
Jaco Reinecke

ESS
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Jaco Reinecke avatar image Jaco Reinecke commented ·

Seems to me similar is being asked here:
https://community.victronenergy.com/idea/22664/idea-battery-discharge-current-limit.html?sort=oldest

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8 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi Jaco,

My experience with ESS is that this is more or less how the system currently performs. Only without the 'programming'.

While the multi is connected to the grid in ESS, surge loads ARE delivered by the grid up to the AC input current limit, and the multi will respond relatively 'slowly' and push power out to match after a second or two up to the inverter limit.


As you mention, when the grid is NOT available, the multi will then supply all the load, surge and sustained.

Batteries can be recharged at set times and the ESS system can be set to not discharge the batteries at other times.



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Jaco Reinecke avatar image
Jaco Reinecke answered ·

Thank you Guy.

You guys did a good job with ESS.

Forgot about scheduled charge times, my apologies. Sorted.

Do I understand correctly?
If I use the option Limit Inverter power, does this literally mean:
- setting the limit to say 50w, limits the power drawn from the batteries at peak, to 50w,
- and not the overall capacity of the inverter, during those peaks, to 50w?

Where do I set: ESS system can be set to not discharge the batteries at other times.
Have not seen that option, or is it a clever combination of options?

Regards
Jaco




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If you set the scheduled charge time window, even to 5% state of charge (so the battery does not recharge from the grid), the battery will not discharge during that period.

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Jaco Reinecke avatar image Jaco Reinecke Guy Stewart (Victron Community Manager) ♦♦ commented ·

Hi Guy,

What am I missing, don't want the batteries to discharge, IF I understood correctly?

Settings are:


Yet is still discharges, after 17:52?

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Hendrik Coetzee avatar image Hendrik Coetzee Jaco Reinecke commented ·

Hey Jaco.

Stupid question - did you check the timezone of the Venus device? And the actual set time?

I believe time is supposed to be set via internet, but maybe something went sideways..

Your scheduled charge settings seems correct as far as a I can see, in order to achieve the "don't discharge, but also don't charge from mains" effect we are looking for.


Scheduled charging exists, and sorta does what I want, but I too would like finer grained control over battery discharge (when allowed, and how much), withou it influencing the PV DC that can directly power loads.

In addition, my experience with tj scheduled charging is that there is still a "trickle" discharge when the schedule kicks in. enough so that I easily loose 5% SOC in +-6 hours. not sure if that is a bug, or something missing in documentation..


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Jaco Reinecke avatar image Jaco Reinecke Hendrik Coetzee commented ·

Time is correct. There seems to be something I am missing, and I don't know what. Same as when I use a Cron Job to change from Keep Always charged to Optimized with Inverter set to 0 watts, to not "lose" any power, it does not "take":

The core behind this Cron job, with loads schedule during the day, is to have a full bank - charge from solar - for taking some more loads off at night, as that 5% loss on Scheduled charging is not cool.

Note: My take on Schedule Charging: It is for Scheduled Charging using utilities when the price per kw is cheap, in SA we don't have that, so to make "Scheduled Charging" fit into a box it was not really designed for, makes not a lot of sense. :-)

So I was shown to use Cron jobs! Now this makes a lot more sense, no?

The Cron Job: (I'm busy tuning)
# Note 1: Manual changes done in GUI will revert back to the Cron job settings at the times specified in the Cron job.
# Note 2: And after a Venus Upgrade, REMEMBER to login and type: cp /data/powerlevels /etc/cron.d/powerlevels
#Note 3: Don't run both options, comment in / out using/removing #


# OPTION 1:

# 9am - Maximum Inverter power
# 2pm - 6pm - Keep Batteries Charged - to store power for use 12am-9am so use all the power to recharge the batts and whatever loads are running at the time
# 5:30pm - 12am - Batteries set back to Optimized.
# 5:30pm - 12am - Set Inverter power to Zero to not use batteries
# 12am - 9am - Limit Inverter to 550w with Optmized already set for 9am


00 07 * * * root /usr/bin/dbus -y com.victronenergy.settings /Settings/CGwacs/MaxDischargePower SetValue -- -1

00 12 * * * root /usr/bin/dbus -y com.victronenergy.settings /Settings/CGwacs/BatteryLife/State 9 - not working yet, still figuring out why.

30 15 * * * root /usr/bin/dbus -y com.victronenergy.settings /Settings/CGwacs/BatteryLife/State 1 - not working yet, still figuring out why.

30 15 * * * root /usr/bin/dbus -y com.victronenergy.settings /Settings/CGwacs/MaxDischargePower SetValue 0

00 22 * * * root /usr/bin/dbus -y com.victronenergy.settings /Settings/CGwacs/MaxDischargePower SetValue 550


# To make a copy of the file, type: cp /etc/cron.d/powerlevels /data/powerlevels


# OPTION 2: Simpler version relying totally on ESS

# 9am - Maximum Inverter power
# 6pm - 12am - Inverter power set to Zero to save batteries
# 12am - 9am - Limit Inverter power to 550w
# 00 07 * * * root /usr/bin/dbus -y com.victronenergy.settings /Settings/CGwacs/MaxDischargePower SetValue -- -1
# 00 16 * * * root /usr/bin/dbus -y com.victronenergy.settings /Settings/CGwacs/MaxDischargePower SetValue 0
# 00 22 * * * root /usr/bin/dbus -y com.victronenergy.settings /Settings/CGwacs/MaxDischargePower SetValue 550

# To make a copy of the file, type: cp /etc/cron.d/powerlevels /data/powerlevels


# Settings explained:
# 07 = 9am 16 = 6pm 22 = 12am
# -1 = Full power
# 0 = Zero inverter power or i.e. 500 for 500w MaxDischargePower
# 1 - Optimized BatteryLife
# 9 - Keep Batteries Charged

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When the grid is connected, the limit inverter feature will limit the conversion from DC supply (dc solar and battery), the rest of the loads will be supplied by the AC transfer through the inverter.

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Jaco Reinecke avatar image
Jaco Reinecke answered ·

Thank you.

Clever idea to use the min of 5% SOC. :-)

So I understood correctly, limiting the inverter power also limits the panel power. It has a use.

Last thought for now:

  • With a BMV shunt, panels connected after the shunt, one can measure the current in / out of the batteries.
  • ESS can already throttle AC in / or panels.

By using a BMV's shunt one can limit the conversion from the batteries by only drawing the pre-set watts from the batts, drawing the balance from the array supplemented by the AC-in, if loads need more.

The reverse also counts.
Installing a larger array with a smaller battery bank, one can limit the charging too because of measurements taking place on the shunt, whilst powering loads by seeing what goes in / out of the batteries, throttling AC-in first and then solar.

Viable?
Or am I missing something?

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David avatar image
David answered ·

Hi Guy and Victron Team,

Terrific discussion above. Very informative to see the Scheduled Charging function in ESS if i read that correctly. If this is an ESS feature, can it be added in the ESS manual (I've had a look and cant see it) and CCGX menu structure if its a top menu (no drama if its a sub menu).

Ignore my comments if it is there.

Thanks again

David DPA Solar (Australia)

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Jaco Reinecke avatar image Jaco Reinecke commented ·

Hi David,

Option for "Scheduled Charging" is under the ESS Menu option.

Regards
Jaco

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I have just updated the ESS manual to include scheduled charging in section 4.3.13, but feel free to expand further yourself David!

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

The Victron Manual for the scheduled charging feature in ESS and Venus-devices has now been updated here in a dedicated scheduled charging manual and here at 4.3.13 Venus-device - ESS Settings

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davidv avatar image
davidv answered ·

Would it be possible for the SOC to change according to the weather days after?

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Jaco Reinecke avatar image
Jaco Reinecke answered ·

Seems to me similar is asked here:
https://community.victronenergy.com/idea/22664/idea-battery-discharge-current-limit.html?sort=oldest

Maybe merge the 2 discussions?

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nicd avatar image
nicd answered ·

If I'm reading the above correct then this seems like quite a simple feature to add that I'd like. In my case I've built my system this year, it's just come to winter and over night my batteries are getting soo cold my BMS is cutting them out. I currently charge them over night via the scheduled charge, if that charge power could be limited independent of the main charge then I could slowly charge them all night rather than just the first 3 hours of my cheap electric. I'm only AC coupled so I don't want to reduce the power all the time as I want the solar to charge them as fast as possible during the day.



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