FoxESS Community - Owners & Installers Forum

Our battery system (nominal 10kW from 4 HV batteries) is housed in our loft so am concerned about temperature although the installer was sure it would be ok. On the user configurable graphs at the bottom of the page I see 'Ambient Temperature', 'Inv Temperation', and 'bat Temperature'.

Plotting these always has the 'Ambient Temperature' the highest, not dropping below 21degrees even at 01:00 in the morning.

The 'Inv Temperation' is slightly lower and rises quite rapidly during periods that the inverter/charger is working as does the 'Ambient Temperature'.

The 'bat Temperature' is the lowest of all by at least a couple of degrees and rises much slower and by a smaller amount when charging or discharging and seems to track the outside temperature more closely.

Looking at the graphs I would have thought that the quite rapid rate of rise in the first two point to them being actively heated by power handling whilst the last one seems a fair guide to ambient temperature in our loft. What do others think, are they incorrectly labelled?

Martin

Whilst I can't recall the difference between Inv and Ambient temps, I do know that I saw them getting very high last summer (above 60) so I installed a bank of 4 small USB power fans across the bottom of the cooling fins, and now I never go above 45. I also installed a heat sink on the top of the inverter, there is a small flat area of metal that also gets very hot.

The battery temp is as expected, rises when batteries charge and discharge, last winter they started getting close to a low of 10 so I'll be building a little enclosure for them for next winter to try and hold them a little warmer. My kit is in a detached but insulated garage so doesn't get overly hot or cold luckily

I have three 120mm 12V PC fans sat on the top of my inverter fins, pulling air up through them. They are powered from a small AC adapter. They've cut about 15C off the peaks I was seeing on the Inverter temperatures. From what I can tell, keeping the power electronics that are generating this heat cool(er) has the potential to substantially prolong the life of your inverter so well worth it IMO.

My batteries are in an uninsulated garage on the North side of the house so while I'm not overly worried about them overheating in summer, they do get really cold in winter. During last December's cold spell they did actually shut down due to the temperatures getting too low for them. An enclosure made from 9mm OSB, sheet EPS and a few battens and bolts made a big difference. Highly recommended since even if the batteries keep going during the cold weather, their rated capacity is measured at 25C, at say 15C, they will lose capacity, both in terms of absolute energy content but also current delivery.

I may add a small tube heater to my enclosure for this winter, to keep the lower battery modules that are in contact with / close to the floor from getting too chilly, since temperature differences within the battery bank will also cause the BMS to derate the performance.

I have the same question as the TS: - What do others think, are they incorrectly labelled?

My outside temp is 15 (Celsius) from the foxess cloud I see the internal temp is 45 which is possible. But the external temp is 46 which would also be possible if this temp is NOT measured outside the device. From it's name "external" I think it's measured outside the device but I'm not sure.

either way I don't think the passive cooling is efficient enough, considering derating above 45.
So are these correctly labelled, or do I have to install/move the external thermometer?

Ambient temperature is the internal temperature of the inverter, InvTemperation is the temperature measured on the rear cooling fins.

One follows the other, the InvTemperation (fins) increases when the inverter is working hard, i.e. lots of solar generation, battery charging or heavy discharging - when it does the Ambient temperature rises at the same time.

When it’s idle Ambient will normally be around 30-35C, InvTemperation around 25-30C

As you can see from what Calum said, a bit if additional cooling drawing air across the rear fins really does help - i’ve got something similar with 3 fans on top switched by a sensor and sucking air upwards, but a simple usb fan such as this https://www.amazon.co.uk/gp/product/B09PBGFFSF will make a significant difference.

It's also worth noting that "bat Temperature" is actually the BMS temperature. The v2.0 app seems to show the actual battery cell temperatures which are often much lower and will give a better indication where you might be with charging rates in winter.

I have my batteries in the loft and had no issues with it being too warm. They are rarely above 30C even in the height of summer. The cold is a real problem for at least 6 months of the year though. Even now at the end of April they are currently about 15C despite being in an insulated enclosure.

I may add a small tube heater to my enclosure for this winter, to keep the lower battery modules that are in contact with / close to the floor from getting too chilly, since temperature differences within the battery bank will also cause the BMS to derate the performance.

I ended up not doing this, instead I put a couple more PC 12V DC fans (92mm ones this time) inside the battery enclosure to circulate the air. It keeps the temperature difference between the warmest and coolest battery cells much smaller, which should help with maintaining batter balance. Because it's bringing up the temperature of the cooler cells it seems to have helped with performance - we were full charging and discharging our battery every day this winter and we were absolutely getting the rated capacity, even when it was pretty darn chilly outside.

I think I'm going to use a pair of solar powered fans.
So a lot of sunshine will speed them up. I don't have them yet but I will see how much power they have and if I keep using them. Here, in summer the temperature will be between 28 and 34 for at least 2 months.