asyrop wrote: ↑Tue Jan 17, 2023 11:10 pm
My installer had no idea about any of this - can you let us know where this information from Fox can be obtained ? Might there be more to explain the various algorithms in the H1 inverters ? - that would be very useful.
Sadly it is quite well known (by developers) that Lithium Ion and Phosphate batteries are affected by temperature, my EV range falls by around 30% in winter and it has it's own internal thermal management system to look after it (and they don't mention that in the WLTP range sheets
).
I think as more people use these technologies the boundaries are starting to become better understood by the people who actual use the systems - so it is more of a setting expectations thing at the moment.
Foxess updated the app late last year as a result of the low temps and the complaints they received, they updated some of the specification sheets to show that whilst the batteries might operate to -10C, they likely wouldn't charge below 0C (sustained) - the info I posted is courtesy of William Eccles who used his test system to generate the error from his app and this is the information the app provides.
asyrop wrote: ↑Tue Jan 17, 2023 11:10 pm
I have seen the various temperatures recorded for my system on the Fox cloud data, but none showed temperatures close to freezing and yet the battery definitely responded to the cold as your attachment describes. Do you know which parameter is determining the limitations to charge and discharge currents ?
Also I am concerned my (new) batteries may have suffered with now reduced capacity. Do you have any information on how they should be calibrated and the rated capacity confirmed ?
This is a complex area, as the battery temperature you see on the Fox charts is taken from a sum of all the temps in the cells of your battery stack - equally the battery temperature probe is actually inside the battery pack on the cells and so it always gives a higher than ambient reading (in my experience about 6C higher), and of course when the battery charges the temperature rises rapidly because the probe is right on the cell itself - the rapid rise is entirely normal but this temperature is normally used by the BMS as part of it's charging and battery health.
All LFP batteries are tested at an ambient temperature of either 25C or 40C depending on the test - the Fox batteries quote their battery capacity at 25C and so you should use ambient as the best metric - the capacity drops slowly below 25C and starts to accelerate below 15C. This next graph isn't based on the Fox battery but is typical of similar LFP batteries when tested which might prove helpful.
Personally I try to keep my battery ambient above 15C (using an insulated enclosure), it gives better capacity but most importantly none of the unfortunate charging side effects of colder batteries.
It's very important to point out that cold temperatures don't damage the batteries, the effects last only as long as the cold temperatures - the batteries soon bounce back when they warm. Unfortunately if the batteries get very hot they can be damaged and their life will be reduced (which is why insulated enclosures are not recommended in warmer months), the LFP batteries used by Fox in solar systems are capable of operating beyond 50C.
Perhaps also worth pointing out that temperature effects all types of battery chemistries in one way or another, however the LFP batteries used by Foxess are an excellent choice for long life, and they are very tolerant to a wide temperature range.
