FoxESS Community - Owners & Installers Forum

I am with Octopus, tariff "GO" and have 4 Fox HV2600 V2 battery bank.
Whilst my batteries never seem to go below 50% SOC I am still being charged by Octopus for all input after the 4 hour night time period.
What settings have I got wrong, or not input because I am sure that all my electricity after the 4 hour period should be F.O.C.
Any help would be much appreciated,

Fox 5.0kw AC inverter
4 - HV2600 Batteries
32 SW Poly 250 panels each fitted with Enphase microinverters
myenergi Zappi 2 charger
Citroen E-C4

I am sure that all my electricity after the 4 hour period should be F.O.C.

There's lots of ways to save (or even make) money on your electricity bill when you have solar panels and batteries, but I don't know that any of them can guarantee you "free of charge" power, albeit it's possible to come close.

Assuming a "self-use" mode of operation is selected:

First of all, during the day your system will generate power which can be used in your home (including to charge an EV for example).
If you're generating more power from your panels that you're using at that moment, the system will divert the excess into your batteries. You have a pretty large array so it's possible you could see more power generated than the batteries can accept. Either way, any power not used on-site or sent to the battery is exported to the grid, and if you're signed up to a suitable tariff you'll get paid a certain amount for each unit.

Once the sun goes down or if there is not enough generation from your panels, the system will draw from your batteries to power your home. Only if there is insufficient solar generation and battery power available will you be pulling from the grid.

In addition to all this, your Fox has settings to tell it to charge your home battery at certain times of day. In your case you'd do that during the off-peak four hours, so that it can power your home during the peak rate times.

During the summer you're likely to have more than enough power during the day, and you probably won't need to charge from the grid overnight. If you're at home during the day you can probably use the Zappi charger to divert quite a lot of energy to your EV.

During the winter, especially if it's cloudy, you'll be charging your house battery from the grid overnight, as well as charging your EV and running any appliances that can run on a timer during that off-peak period.

Depending on how much electricity you use at different times of day, different times of year, what you cook with, and how you heat your home, etc.

Bear in mind that your four HV2600s have a nominal capacity of about 10kWh, but probably 8-9kWh usable, which may or may not be enough to get through a day. If there isn't much / any sun and your battery has run out then you'll be drawing from the grid at peak rate.

Also bear in mind that your inverter can only convert battery and solar power into AC or "mains" power at 5kW. If you tried to charge your EV using "Fast" mode on the Zappi (7kW) or maybe if you had an electric shower (10kW?) then even with a fully charged battery and in bright sunshine, you're still going to be pulling power from the grid.

Hopefully this clarifies a bit about how your system can save you money. Essentially you want maximise the use of the generation you get from your panels, and ensure that if you're charging from the grid you're not preventing the storage of "free" PV electricity.

Calum
Many thanks for your reply.
You were right the "self use " mode had not been selected, that has now been corrected.
I do not believe my original post was very clear, what I was trying to say was I assumed that most if not all of my electricity after the night time charge period would come from the battery and not the grid thus being F.O.C. just being charged at the reduced night time rate.

I am still seeing a little supply coming from the grid late afternoon/evening but very little, a great improvement, thank you.

Despite the battery has not gone below 63% fully charged in the meantime the lowest energy consumption figure I have seen is 1.9 - 4.0 with no clear day's on the overnight charge period.
Am I on the right track or should I being doing better regarding my take from the grid!

Any further help would be much appreciated.
Regards

dellpitch (Norman)

Hi Norman

If you've got plenty of battery capacity going spare, you can reduce (or eliminate) the charging the battery does overnight. Or, you can just set a charge period for the Octopus Go cheap rate, and allow the grid to 'take the load' during that time, meaning your battery has room to capture the following day's solar PV gain.

I have not been charging the house battery overnight since mid April, at least not by default. I have given it a bit of a boost here and there when we've had a few cloudy days on the bounce.

Hi Callum

Many thanks for your reply, I confess that I am lost as to how to proceed.
Do I go into the battery settings on the inverter and set the max S.O.C at say 35%, it is now set at 96%, or do I go into the on-grid setting and set the power limit to???

As you can tell I am a newbie out of my comfort zone by a mile!

It is great what you have achieved a result that I would very much like to emulate.

As always any further help would be much appreciated.

Norman

Hi Norman

You can just tell the system not to charge at all overnight.

The FoxESS systems have two "charge periods" (sometimes called "force charge"). If you define a force charge period in the settings, the battery will not discharge during that time. Additionally, you can tell the system you want the battery to charge from the grid during that charge period. As you've already seen you can additionally tell it not to charge from the grid beyond a certain SoC. When charging from solar PV, the system will charge the battery all the way to 100% SoC given enough energy.

You can set a low MaxSoC to prevent it from charging, but you'll be pulling power from the grid during that time. If your battery has sufficient charge to get you through to when your panels will be generating again, you maybe don't want any charging periods active at all.

Alternatively you can just set, say, a short (30 minute?) charge window during your offpeak time, possibly combined with a MaxSoC, in order to avoid putting "too much" charge in the battery and not having space to store the "free" excess PV generation.

Of course as we go through the year this will change; in December you'll get next to no solar gain, and be looking to charge to full during the off-peak power window. But depending how how much power you use at home, how big the batteries and solar array are, and of course what the weather does, I'd expect you to be able to go from some time in April to some time in September with minimal grid imports.

Bear in mind that the inverter constantly draws a small amount from the grid to confirm that it's still connected, so you will always end up pulling ~0.5kWh from the grid every day regardless.