FoxESS Community - Owners & Installers Forum

Dear FOX ESS Support Team,

I am using a FOX ESS T15-G3 on-grid inverter with 10 × 585W BF Jinko panels. I’ve observed that even brief grid outages (5–15 minutes) cause a disproportionately large drop in total daily production, even though weather and irradiance remain consistent.

For example:

• On May 25, the grid was out from 07:46 to 07:51 AM. Total production: 23.6 kWh.

• On May 26, outage from 11:23 to 11:42 AM. Total: 27 kWh.

• On May 27 (no outage), production: 31 kWh.

Based on app monitoring and performance tracking, I’ve noticed:

• The inverter takes several minutes after grid restoration to stabilize and resume full output.

• It seems to re-scan MPPT tracking from scratch, instead of continuing from previous optimal values.

• This behavior causes underperformance far beyond the actual outage duration.

I’d like to know:

• Is this behavior expected with the current firmware?

• Are there any firmware updates available to optimize post-grid-outage recovery?

• Can you recommend settings or configurations to improve MPPT retention or re-connection time?

I am quite worried about this behavior of inverter as grid outage for short period of is common in my area. and this impacts significantly power production.

Thank you in advance. I am attaching screenshot of graph for better understanding.

Regards

From my understanding to it inverter is working as expected. It can’t simply resume from the previous values. Should only take minutes to resume.

Right, So grid outage would result significant/huge reduction on total production/day ?

If grid outage is around 8AM then that day peak is 3.5KW
and without grid outage peak value is 4.5KW.

is it normal for fox inverter ?
because my another system (Inverex Brand) doesn't give such bad performance for same condition.

EDIT: I expect inverter to take time to resume but why it doesn't get to usual peak production around?
Moreover, please guide me about official support/company's warrant claim dept ?

Bump

Doesn't make sense, the mppt should ramp to full speed within a few minutes, an outage in the morning shouldn't cause a limit all day.

I would double check you're on the latest firmware and then carry out a full restart of the inverter and monitor.

Will wrote: ↑Thu May 29, 2025 11:13 am Doesn't make sense, the mppt should ramp to full speed within a few minutes, an outage in the morning shouldn't cause a limit all day.

I would double check you're on the latest firmware and then carry out a full restart of the inverter and monitor.

Thank You
Below is detail of inverter firmware data. Please advise what should I do next ?

can I upgrade firmware on my own if update available ?

Hi, those appear to be old firmware versions. Only your installer or fox support can update the firmware. It's not yet end user accessible.

Right. Thanks Alot.
I will try to get it upgraded. Will share details here.