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Battery backup earthing - PME supply

vantech

Hi, 

I am installing a battery (Alpha ESS) to a PME system. 

The battery charges during off-peak and discharges during the day during peak hours. There is no solar. 

This relatively straight forward and will be notified to the DNO. 

The system features a back-up supply, where if the grid supply fails, a set of loads can be powered from a dedicated “backup” output on the inverter. This output is already separate from the grid input. 

The question I have is around earthing. When in normal operation the inverter is connected to the PME supply via the MET in the distribution board and the “backup” output is earthed through this connection. When the grid fails (outage, for example) my thinking is that the PME “earth” cannot be relied upon for the backup circuit (lost neutral for example). 

What would be the best course of action to resolve this situation? 

  1. Earth rod at the customer premises connected to the MET? 
  2. Rely on the manual and it’s wiring diagram? 
  3. Other? 
     

The inverter manual gives no indication. 

Thanks.

Battery Inverter Manual: 

https://www.alpha-ess.com/Upload/Images/20190814093353_165226.pdf

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  • Former Community Member
    0 Former Community Member

    This is quite a good link as it indicates the actual output is limited to half the battery capacity as a product of discharge current and voltage (ie 0.5 C if I'm using the correct terminology) and it would appear that the warranty is either 10 years or earlier if the declared kWh charge/discharge cycles have been used up…..

    I don't know the UK price but it would be good to work out the cost per kWh extracted from the battery using the declared capacity and 90% DOD cycles compared to present domestic costs of around 18p per kWh.

    Regards

    BOD

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  • Former Community Member
    0 Former Community Member

    This is quite a good link as it indicates the actual output is limited to half the battery capacity as a product of discharge current and voltage (ie 0.5 C if I'm using the correct terminology) and it would appear that the warranty is either 10 years or earlier if the declared kWh charge/discharge cycles have been used up…..

    I don't know the UK price but it would be good to work out the cost per kWh extracted from the battery using the declared capacity and 90% DOD cycles compared to present domestic costs of around 18p per kWh.

    Regards

    BOD

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