EV overnight grid import/home battery usage strategy and Fox ESS settings

[Robbie]

Hi,

looking for a bit of advice on setting up a strategy for my new system:

E-on Next Drive Fixed v7 (6.7p per kWh 00:00 to 07:00)
E-on SEG Next Export Exclusive v2 (16.5p per kWh)
18 PV solar panels (8.1 kW max)
Fox ESS Inverter H1&AC1(G2)
Fox ESS EP11 10kWh Battery
Zappi Smart EV Charger 7 kW

I have two issues I would value your input on:

1) I set up EV charger on Eco+ to fast charge my car from the grid during the low import overnight rate last night using Mode Scheduler/ Force Charge/Grid charge not Enabled. This worked. My EP11 started the night at MN with 85% SOC and stayed at this till 7 am, the car was fully charged overnight from the grid, but I didn't extract any value out of the EP11. I am thinking to try tonight a slightly different approach tonight:

Mode Scheduler/ Force Discharge MN-07 am/Min S0C 25%/Max SoC 90%/FD SoC 25%/Max AC Power (FDPwr) 1000W.

I am hoping that during the 7 hr overnight period, the7Kw Zappi will draw at 1kW from EP11 for free and at 6kW from the grid. This should leave a bit of SoC left on EP11 for 7-10 am before solar generation starts recharging it tomorrow.

WIlLL THIS WORK? !!!!

2) Second issue is I noticed there is clipping of solar export to grid at 5kW (see below). During sunny days/10am-4pm. The energy coming off the roof seems limited to 5KW for export if I don't use it, and everything generated above this is wasted, whereas if I do use it, the roof can send 8-9 kW down through the inverter and send some of it to load and up to 5 kW of the rest to grid. Is this right? Have they given me an underspecified inverter? Or is this limit set by UK Power Network? Or can it be manually altered on the inverter settings?

Thanks all,

Rob

[Dave Foster]

On 1), the mode scheduler settings for force discharge don't use Max SoC but you usually have to set it to valid number to save the schedule. Also just to add and you probably know this already but you can't use Schedules and Charge Periods together it's one or the other.

Mode Scheduler/ Force Discharge MN-07 am/Min S0C 25%/Max SoC 90%/FD SoC 25%/Max AC Power (FDPwr) 1000W.

Specifically about these settings, schedules are different to charge periods in that they start and end at HH:MM:00 whereas schedules start at HH:MM:00 and end at HH:MM:59 so use 06:59 instead of 07:00 or it will end at 07:00:59 and could overlap with the next schedule.

Your FDPwr at 1000 watts is the battery discharge limit and so whatever your house load is will be taken first before anything goes to the car i.e. if your house load is 300 watts, your EV will get 700 watts of battery power, the rest from grid.

When you use schedules always remember that if you change minSoC it will be left at what you set it when the schedule ends, so if you wanted it to be 10% from 7am onwards you'll need to set a short schedule beginning at 7am ~ something like set Self Use workmode and a MinSoC of 10%

What size inverter do you have is it H1 5kW or 6kW ? (this is likely what your G99 limit will be) and how is the string setup - 2 strings of 9 ?

Normally you would spec an inverter approx 15%-20% over the maximum inverter capacity so 8.1kWp is a big array and will be prone to clip on the very sunny days as the AC output of the inverter can never be more than it's maximum capacity (but great in winter when irradiance is low)
You can charge the batteries and have max AC output at the same time which is why in the morning the peak power is higher but as soon as the battery is full it will clip at the inverter rating.

The only way to change your AC output is to increase the size (and probably model) of the inverter; that will need you to re-apply for a larger G99 export limit which could be rejected by your DNO.

[Robbie]

Thanks Dave

I've made the suggested adjustments and will give it a go. Will feed back the results. The inverter is H1-5.0-E-G2

Rob