FoxESS Community - Owners & Installers Forum

Hello forum.

I had a Fox ESS solar system with battery storage installed at my home a couple of weeks ago and am gradually getting accustomed to how it works, but am puzzled by some things. My contact at the installers is still away on Christmas break, so I thought I might ask here to see if I can get any quicker answers.

The system is set to Self-Use work mode and scheduled Grid Charge Setting is disabled, as the installers left it.

The first question is whether the charging current of the battery is end-user adjustable. It seems to be limited to 2A, equivalent to 800W, at the moment so battery charging is quite slow even when we've got a surplus of energy being generated by the panels and plenty being exported. A full charge would take almost 13 hours at that rate. The recommended charge current for the EP11 battery is 13.5A according to its datasheet. I haven't found anywhere that I can change this setting. Is it installer-only?
(Edit: Disregard the paragraph above. I've learned from other posts that the charge current can be adjusted from the inverter front panel.)

Another question is regarding charging the battery from grid. I haven't enabled Grid Charge Setting as I haven't switched to a storage-friendly tariff like Octopus Flux yet, but I saw the battery started charging from the grid between 00:45 and 05:45 this morning from 20% up to 60%. It has started charging from grid again at 21:40 this evening, from 20% up to 30% so far. These are not cheap electricity times on my current tariff, so this is not ideal.

There was a nice bit of sunshine today, so we had 2.5kW of solar generation as soon as the sun cleared the hill to the east of my house at 09:50, climbing to 3.7kW around midday. For some reason, battery charging didn't resume until 12:35, so most of that generation was being exported. Why didn't it resume charging the battery as soon as there was a surplus of solar generation?

Here's today's graph from Fox ESS Cloud:
I'd be grateful if anyone could enlighten me.

JM

It's unusual for the charge current to be limited in settings unless the installer has changed it - which as I say is unusual.

Where are the batteries located?, as they will be charge throttled when the temperature falls towards zero and will not accept charge at or below 0C

If you use the Fox V2 app it will show you the battery temp (this is the lowest cell voltage in the pack) - what does that show ?.

On the random charging - i'm assuming you do not have any charge periods set ? - when they are not being used they must be set to 00:00-00:00

What is your minSoc and 'minSoC on grid' (aka battery reserve in the V2 app) set to ? - again this sounds temperature related as the BMS will request a slow charge in an attempt to warm the batteries when the temperature gets very low.

Thanks for your response.

I've just been outside to inspect the inverter. I checked through the control panel and the maximum battery charge current is set to its highest value, 40A. However, the FoxCloud 2.0 app shows a Max charging current of 2A under Device -> Inverter -> Detailed Parameters -> Battery Information.

The battery is outside next to the inverter, so it has been subject to the freezing weather that we've had the last couple of days. Right now the app is reporting the battery temperature as 1.5°C.

I don't have any charging periods set. They're both 00:00-00:00 and "charge from grid disabled".

Battery Reserve Capacity (MinSoC on Grid) is set to 20%.
System Min SOC (MinSoC) is set to 10%.

I did just discover that the date and time on the inverter had not been set correctly. It was set to 30th September 2024 at around 10am, when it was 15:00 really. I've corrected the date and time now.

Ok thanks, the app under battery is reporting what the BMS will allow - so the 2A is set because of low temperatures and the inverter is not allowed to override that.

If that’s going to be a problem do a quick search on insulation, it’s easy enough to build a temporary enclosure that will help.

Hello Jason. You are not alone. We had our system installed on 28 December by ECH and had exactly the same issues as you’ve experienced. It’s been quite a stressful few days but finding forums like this really helps. What we don’t understand is why the installers aren’t suggesting or even providing insulation options, they are missing a trick. It’s the not knowing that causes the stress, once you know you know and can relax and stop worrying that something is very wrong with your system. It’s certainly a learning curve, good luck and I’m sure we’ll see each others future posts

Thanks everyone for the responses.

After correcting the inverter's clock on Saturday, and setting the scheduled charge-from-grid period to 02:00-05:00, I've observed much more expected behaviour the last two nights.

On Saturday night when it was still freezing outside, it started charging as expected at 02:00 but at a slow rate of about 0.85kW. It It charged from 58% to 80% over the three hours.

Last night, with the weather being much milder, it again started charging the battery at 02:00 at a rate of 4.15kW, then jumped to 5.43kW after 40 minutes for another hour. It charged from 20% to 100%. The house has been running from battery all day and it's still at 52% now, which is nice.

One minor weird thing was that yesterday, the battery drained to 20% at around 14:35 and stopped being used, but it continued to drain very slowly down to 16% by 01:00 this morning. The system did a brief 15-minute top-up charge at that time to bring it back to 20%.

My system is mostly behaving as expected now, but I'm still seeing occasional unexpected charging from grid at non-ideal times.

The system is set to charge from grid from 02:00 to 05:00, being the Octopus Flux cheaper rate period.

This morning, the battery was at about 44% at 00:00 and unexpectedly started charging at that time. It charged up to 60% by 01:30 then stopped, then the scheduled charge kicked in at 02:00 and took it up to 84% by 05:00: On the morning of the 8th, it started charging as expected at 02:00 (20%), but continued until 07:50 (60%), 2h 50m past the end of the cheap rate period: The 60% SoC seems to be a common theme here. My concern is that the system is choosing to charge the battery from the grid outside of the cheapest rate period.

The charge power is really low, that only happens when the BMS is throttling the charge because of temperature (or at minSoC which you are not), the V2 app will show the lowest cell temp which is what everything triggers from - on the 4th it was reporting 1.5C and at 0C the batteries stop charging all together so much of this is the BMS trying to maintain it's operation.

As soon as the ambient temperature rises you will see your charge rates recover, I can't see what inverter spec you have but at 20C the batteries will charge from grid at just under the inverters rated capacity i.e. 5kW would charge at approx 4.8kWh.

If the batteries are outside they will be affected by cold weather (mostly affecting the charge rate) but when they fall below 0C they will stop discharging soon after - a lot of people build an insulated enclosure for this time of year which helps stabilise the temperature - there is a link here viewtopic.php?p=5465 to an example of what other users have used but if you search for insulation there will be quite a few hits.

Janey wrote: Sun Jan 05, 2025 5:53 pm Hello Jason. You are not alone. We had our system installed on 28 December by ECH and had exactly the same issues as you’ve experienced. It’s been quite a stressful few days but finding forums like this really helps. What we don’t understand is why the installers aren’t suggesting or even providing insulation options, they are missing a trick. It’s the not knowing that causes the stress, once you know you know and can relax and stop worrying that something is very wrong with your system. It’s certainly a learning curve, good luck and I’m sure we’ll see each others future posts

Very interesting, Janey. I had mine installed by ECH last week, 12th Jan, and like you, am digging around trying to understand it. I wish they'd actually give you better information at installation, and yes, I'm now thinking that had I known then what I know now, I'd probably have had the battery installed inside to keep it warmer than it currently is in the garage. I'm going to look around for what others are doing about insulation (I wonder if it's safe!) Ho hum, let's keep learning!