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Trendywendy
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November 1, 2023
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Why is my system drawing from the grid instead of using full Foxess batteries

  • November 1, 2023
  • 8 replies
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Good evening, we’re generally very happy with our PV and battery system, but a couple of months ago, the system started misfunctioning.  Although the batteries are full, a percentage of the load is constantly being drawn from the grid, while a portion trickles from the batteries.  This is irrespective of the load, I.e. when we’re cooking or when we’re sleeping, some draws from the grid and some from the battery.  Obviously this is incurring costs that we needn’t have.  The battery supplier Foxess says that it could be a CT clamp problem.  Does anyone else have a suggestion or confirmation?  The system is  2 years old and was installed by a National company who are now in liquidation!

Best answer by BPLightlog

Updated on 26/09/24 by Chris_OVO

Hi @Trendywendy , it sounds as though there’s been a change in your system parameters if you’ve only seen this trickle recently. 
The CT (dependent on the system) often has an offset applied via the inverter configuration which ‘levels’ the measurement it makes. The CT monitors and reports on current flowing through the cable it’s attach around which the inverter then uses to calculate what’s needed from either battery or grid. 
The CT may have moved. 
It may need re-balancing.

The inverter firmware may have been updated causing a change. 
It is difficult to determine exact cause remotely. 
Do you have any friendly installers locally who might take a look?

Check out this similar topic that could also be helpful:

8 replies

BPLightlog
Super User
BPLightlogSuper UserSolved
Super User
November 1, 2023

Updated on 26/09/24 by Chris_OVO

Hi @Trendywendy , it sounds as though there’s been a change in your system parameters if you’ve only seen this trickle recently. 
The CT (dependent on the system) often has an offset applied via the inverter configuration which ‘levels’ the measurement it makes. The CT monitors and reports on current flowing through the cable it’s attach around which the inverter then uses to calculate what’s needed from either battery or grid. 
The CT may have moved. 
It may need re-balancing.

The inverter firmware may have been updated causing a change. 
It is difficult to determine exact cause remotely. 
Do you have any friendly installers locally who might take a look?

Check out this similar topic that could also be helpful:

Bring me Sunshine ~ E&E {Solar PV, Battery Storage, Hybrid EV, ASHP and Home Assistant automation}
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    TrendywendyAuthor
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    November 1, 2023

    Thank you for your prompt reply.  We have requested visits from our usual electrician and from a couple on the HIES register but to no avail.  It seems like we need to try again. 

    BPLightlog
    Super User
    BPLightlogSuper User
    Super User
    November 1, 2023

    Try the MCS register - they tend to specialise in micro generation systems. 
    https://mcscertified.com/find-an-installer/

    Bring me Sunshine ~ E&E {Solar PV, Battery Storage, Hybrid EV, ASHP and Home Assistant automation}
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      TrendywendyAuthor
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      November 1, 2023

      Thank you for the link.  I have just emailed a fairly local contractor on it who I wasn’t aware of, so fingers crossed and I’ll keep you posted.  Thanks again for your help.

       

        BPLightlog
        Super User
        BPLightlogSuper User
        Super User
        November 1, 2023

        Thank you for the link.  I have just emailed a fairly local contractor on it who I wasn’t aware of, so fingers crossed and I’ll keep you posted.  Thanks again for your help.

         

        Hope you find them helpful. 
        Just one other thing .. looking at the image you posted, the battery voltage is shown as 212v which is low for supply. 
        As you will know, the UK works on 230v and there are upper and lower limits for this 

        +10% (= 253v)
        -6%   (= 216.2v)

        So that suggests that the battery output voltage is lower than it should be which might also be causing the problem 
         

        Bring me Sunshine ~ E&E {Solar PV, Battery Storage, Hybrid EV, ASHP and Home Assistant automation}
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          TrendywendyAuthor
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          November 1, 2023

          Fair point, but looking back at photos over the months, it has always been reading that voltage even when the system was performing properly, however, as and when we get a visit from an electrician, I’ll point it out in case he agrees it’s relevant.  
           

            Emmanuelle_OVO
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            Emmanuelle_OVO
            Retired Moderator
            November 2, 2023

            Keep us posted @Trendywendy 

            Renewable Energy? Big Fan.
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              TrendywendyAuthor
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              November 2, 2023

              I will do, I know other people have experienced something similar with power coming from the grid instead of their battery, but that is usually when there is a strong fluctuation  - whereas ours is constant and happened quite suddenly one day in July. 

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