Hi,
Does anyone have any studies, reports on how the longevity of LiFePo4 batteries is affected by different ranges being used?
e.g. for longevity, is
0-100%
20-100%
0-80%
20-80%
best, and by how much?
A lot of people seem to have opinions on this but was wondering does anyone know of any proper research here?
Many thanks,
Mark
There are a lot of research papers about for LFP batteries but they tend to focus on specific things like ageing, or temperature - the main problem being that LFP batteries do not have enough historical data to study as the chemistry is fairly new.
This is a very good video that explains some of the realities
The main thing to remember is that Fox have already limited the batteries to 90% DOD and they provide warranties for their batteries being charged by their BMS systems which do require regular 100% charge cycles to maintain SoC accuracy. Best advice is to use them within the Fox specifications temperature, currents and their battery warranty will provide all the guarantees you need.
This is a very good video that explains some of the realities
The main thing to remember is that Fox have already limited the batteries to 90% DOD and they provide warranties for their batteries being charged by their BMS systems which do require regular 100% charge cycles to maintain SoC accuracy. Best advice is to use them within the Fox specifications temperature, currents and their battery warranty will provide all the guarantees you need.
Thanks Dave!
That makes sense!
when you say:
"which do require regular 100% charge cycles to maintain SoC accuracy"
Any ideas how often 'regular' is?
1x per month
1x per week
1x per day?
That makes sense!
when you say:
"which do require regular 100% charge cycles to maintain SoC accuracy"
Any ideas how often 'regular' is?
1x per month
1x per week
1x per day?
It’s best to do it monthly, it won’t damage them if you don’t but you’ll see the accuracy of the SoC gets worse with occasional jumps as it re-evaluates the Soc from the cell voltages.
I found this one quite interesting
https://iopscience.iop.org/article/10.1 ... 111/ad6cbd
There's also https://www.sciencedirect.com/science/a ... 1722000283 and https://www.mdpi.com/1996-1073/14/6/1732 which cover aspects like calendar degradation.
Personally I do 100% once a week, 10% once a month via an automation. It'll do it more often in certain circumstances (for example, if forecast PV for the day is very low, it'll use the full range instead for a bit of extra arbitrage to make up for the lost generation).
It's not worth doing the calibration cycles manually, you might as well just stick to the full range rather than trying to keep track. Also, underutilising the battery is just as much of a waste, due to calendar degradation (for example, sticking to 20-80 all the time, 0.6 full cycles daily, would mean you'd run out of warranty years, and the battery capacity would have decreased anyway due to the passing of time). It's a bit of a balancing act.
Calendar degradation is (relative to cycling) more important on LFP, whereas with NMC batteries the cycling is a much bigger factor.
https://iopscience.iop.org/article/10.1 ... 111/ad6cbd
There's also https://www.sciencedirect.com/science/a ... 1722000283 and https://www.mdpi.com/1996-1073/14/6/1732 which cover aspects like calendar degradation.
Personally I do 100% once a week, 10% once a month via an automation. It'll do it more often in certain circumstances (for example, if forecast PV for the day is very low, it'll use the full range instead for a bit of extra arbitrage to make up for the lost generation).
It's not worth doing the calibration cycles manually, you might as well just stick to the full range rather than trying to keep track. Also, underutilising the battery is just as much of a waste, due to calendar degradation (for example, sticking to 20-80 all the time, 0.6 full cycles daily, would mean you'd run out of warranty years, and the battery capacity would have decreased anyway due to the passing of time). It's a bit of a balancing act.
Calendar degradation is (relative to cycling) more important on LFP, whereas with NMC batteries the cycling is a much bigger factor.
Thanks WyndStryke for your thoughtful reply (and for the papers), much appreciated! 
What SoC range do you typically use for your batteries then?
What SoC range do you typically use for your batteries then?
It changes on a day to day basis, anywhere from 14-92 to 20-84 (my automations will tweak it based on the PV forecast / weather forecast / etc), but I will also be cycling in the middle of that range as well (again, dependant on things like cell temperature / PV / weather / etc). I also adjust charge and discharge rates based on those criteria. On very hot days etc it will be using the slowest possible charge and discharge rate and no mid-range cycling (a high cell temperature causes increased cell degradation). When it is cold, it will be more aggressive, to generate warmth.What SoC range do you typically use for your batteries then?
So I'm using more like 0.8-1.0 full cycles daily even if I don't hit the extremes. That's only possible on particular tariffs.
I would honestly expect FoxESS to manage this properly. The only thing as a enduser I should set is the MinimumSoC and the rest the system should "automagically" manage.
System Setup (Austria): Inverter: STAR-H3-12.0-E / Battery: STAR EP11 (10.36 kWh) / Panels: 24x Canadian HiHero 440 Wp (10.56 kWp total)
That's how 95% of people do it. I tend to go above&beyond. The BMS will already reduce the charge rate as you near 100%, or if the battery is very hot or cold. I just put stronger limits on things.
Last edited by WyndStryke on Thu Aug 07, 2025 11:55 am, edited 1 time in total.
Hi All.
I have an EP11, installed during February as part of a new solar install (Fox 6kW hybrid inverter, for what it's worth).
I have set the SoC to 15% (I think it was at 20% by default) and allow it to charge up to 100%, which over the first six months it has done so more than 50% (maybe as much as 80% plus) of days - though winter is of course coming
I don't do forced charging or discharging - I just let it fluctuate up and down according to solar availability and our usage. During the hot nights, it goes down to 15% due to air con and fan usage.
Is this basically fine and an OK operating mode for this battery?
Ian C
I have an EP11, installed during February as part of a new solar install (Fox 6kW hybrid inverter, for what it's worth).
I have set the SoC to 15% (I think it was at 20% by default) and allow it to charge up to 100%, which over the first six months it has done so more than 50% (maybe as much as 80% plus) of days - though winter is of course coming
I don't do forced charging or discharging - I just let it fluctuate up and down according to solar availability and our usage. During the hot nights, it goes down to 15% due to air con and fan usage.
Is this basically fine and an OK operating mode for this battery?
Ian C
Yes it's fine, the important thing is that it gets to 100% from time to time as it's in the last few % the batteries balance all of which will improve the accuracy of the batteries SoC reading.
In winter it's likely you won't get anywhere near 100% some people use the eco tariff's (EV or eco 7) to charge during the night on the low tariff and then use the power during the day when the tariffs are high. If you don't do that you might want to give it a monthly charge from grid to 100% just to keep it reporting accurately.
Equally you can set the battery minSoC to 10%, it is rated for that and it won't effect the warranty or guarantees plus you'll get all the capacity you have paid for - the only time it might be better to be at 15% is when it is very cold over winter, particularly if the batteries are stored externally (and don't have the internal heater option).
In winter it's likely you won't get anywhere near 100% some people use the eco tariff's (EV or eco 7) to charge during the night on the low tariff and then use the power during the day when the tariffs are high. If you don't do that you might want to give it a monthly charge from grid to 100% just to keep it reporting accurately.
Equally you can set the battery minSoC to 10%, it is rated for that and it won't effect the warranty or guarantees plus you'll get all the capacity you have paid for - the only time it might be better to be at 15% is when it is very cold over winter, particularly if the batteries are stored externally (and don't have the internal heater option).
Thanks, Dave.
Interestingly, I had a look at the behaviour in February.
Feed in to the grid occurred at some point on the following dates after the mid-Feb install (implying the battery was full): 14th, 15th, 17th, 18th, 19th, 21st, 22nd, 23rd, 24th, 25th, 26th, 27th, 28th (or perhaps more simply, not the 16th and the 20th). I've got an array of panels matching the hybrid inverter capacity facing 5-10 degrees west of south without obstruction, so even in winter, it was producing decently.
Half or more of these were only for short periods around the middle of the day. I suppose this might mean that the battery couldn't handle all the hybrid inverter's spot output on a bright day, so the excess was diverted to the grid - in which case the battery was probably not full. However, a number of days did have sustained periods of feed in, with the usual arc starting in the middle of the day then decreasing through to sunset - in which case the battery probably was full.
So, even with a few of those during bright winter days pushing the battery to 100%, all should be good without me needing to do anything, if I've understood you correctly.
Ian C
Interestingly, I had a look at the behaviour in February.
Feed in to the grid occurred at some point on the following dates after the mid-Feb install (implying the battery was full): 14th, 15th, 17th, 18th, 19th, 21st, 22nd, 23rd, 24th, 25th, 26th, 27th, 28th (or perhaps more simply, not the 16th and the 20th). I've got an array of panels matching the hybrid inverter capacity facing 5-10 degrees west of south without obstruction, so even in winter, it was producing decently.
Half or more of these were only for short periods around the middle of the day. I suppose this might mean that the battery couldn't handle all the hybrid inverter's spot output on a bright day, so the excess was diverted to the grid - in which case the battery was probably not full. However, a number of days did have sustained periods of feed in, with the usual arc starting in the middle of the day then decreasing through to sunset - in which case the battery probably was full.
So, even with a few of those during bright winter days pushing the battery to 100%, all should be good without me needing to do anything, if I've understood you correctly.
Ian C
Ok no problem, keep an eye on it - it’s not essential and if it doesn’t hit 100% for a few months you just might start to see jumps in SoC and drifts in accuracy but theres no damage as a result.
Just as a quick FYI December is by far the worst solar month, followed by January, February is a big improvement
Just as a quick FYI December is by far the worst solar month, followed by January, February is a big improvement
July felt like it was bad (compared to the sunny weather earlier in the year), but I was still 9% above the PVGis and installer estimates despite the seemingly endless cloud cover. That really surprised me.