question

dayandnight avatar image
dayandnight asked

relay assistant based on charge state - how does it work

Hello Victronauts!

I need your help. I am trying to find out how I can use the relay assistant based on charge state.

It is possible to select during setting the assistant on four different "WHEN" states:

  • when charging
  • when not charging
  • when bulk finished
  • when absorption finished

I have a three phase ESS system with a AC / grid based PV system and a pylon battery bank with 17,2 kW useable energy. I am trying to find out how and when the relay will be set / reset.

I setup the assistant in the Multiplus-II for phase no. 3 according to the followings screenshot:

and the relay is set indeed when bulk is finished. Great! I understand! But it is never reset as I thought when absorption is finished. Okay it can happen during absorption phase, based on the needs of energy and / or PV harvest that the absorption switches from absorption after 20, 40 or 60 minutes back to discharging or bulk phase. But never, NEVER this was obviously the sign for "absorption finished" and the relay always stays SET and was never reset, as long as I investigated the system.

Question 1:

So what has to happen or what has to occur that the relay is switched off, based on "absorption finished". Who can explain it to me?


Same with my investigation with the relay assistant on phase two:

I am sure it is some how naive, but I just thought when the Multiplus is not charging the battery it switches the relay ON and in the same sense when it is charging it sets relay OFF.

But after several days of investigation, the relay stay always OFF and there is no effect in the relays contact when charging or not charging the batteries.


Question 2:

What is wrong in my mind and my thinking?


Is there any body who has experience in this and can explain it to me, please?

Thanks

DayAndNight



relay assistant
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dayandnight avatar image dayandnight commented ·

Hello Specialists, hello community,

nobody out there who can help me on this? Or just link me to some docs where I can find some information for the assistants in detail.

I know this page with give some overview for the assistants. But it is more a listing or directory with screenshots of VE-Config what assistants are available and do not explain them in detail.

I gamble around to find out how it works. But it is somehow a pain to do reverse-engeneering. ;-)

I would appreciate your help very much! Thank you!

DayAndNight

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @DayAndNight

when the battery controls the charging (as with all CANbus connected batteries), and ESS, charge state might not be what you expect it to be. It can be 'bulk' when it's actually discharging.

Maybe it's better to use SOC as a trigger?


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dayandnight avatar image dayandnight commented ·

Hi Daniël,

thank you for the feedback. Yes, I found out, that it doesn't behave as I hoped, with bulk, charging etc. ..

My problem: I want to control my PV system to avoid grid feed-in. My PV-system is 3 phase grid connected with 18 micro inverters from ae-conversion. I have for each phase (= 6 inverters) one data-logger which is able to switch the connected inverters from 100% to 60%, 30% or 0% power.

My idea is to switch two of 3 phases PV from 100% to 0% power at SOC level 100% (12:01) and switch the third phase to 30% power - I set the assistant to SOC above 99% ( which triggers the assitant already above 99,5% but no problem )

Please see example below. It is somehow a little bit to early, in the sense when chraging current is very low or 0 A but this doesn't matter. Normally the PV power with one phase at 30% power only and both other 0% is strong enough to keep charging.

What I am looking for is a way to realize when ESS is switching later (13:27) from charging to discharging because there is a need for energy / an AC-Load (grid based) in the system. Therefore I looked into the assistant for charging / discharging. Actual I detect with a second assistant SOC level below 96% to switch the PV system back to 100% power for all three phases.

I tried also with assistant with AC-Load is higher as 1.500 W for 10 seconds to detect big load for switching PV system power back to 100% but it didn't work either.

Perhabs you have a better idea to switch my PV system back to 100% other than to wait until SOC is below a specific value, I use in the moment 96%

Therefore I wanted to understand all the possibilities of the relay assistant how it works to get an idea how to do. In the moment, without knowing and understanding it is more guessing than engineering! ;-)

Your help is very welcome in this.

DayAndNight


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