Hi All,
Had my bank of five LV5200's for almost a year now and apart from a few minor issues (see my other posts here) all has been really good. Throughout this time, the SOH has always been reported as 100%, but yesterday I noticed this has dropped to 99%; the capacity of my bank has now dropped by 1% (26kwh is now 25.74kwh). I know these (and all) batteries degrade with time/charge cycles, but just wondered if anyone else has seen their SOH drop and by how much over what time? If we assume 6000 cycles (best case, I suppose), that makes around 16 years assuming one cycle per day. 15 years is a good design life and if they drop at 1% per year; after 15 years the capacity will have reduced to 85% (around 22kwh). Not too bad and then time to think about replacement, which by then should be a lot cheaper per kwh than it is today.
Cheers, Jerry
State of Health (SOH)
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Dave Foster
- Posts: 1328
- Joined: Thu Oct 13, 2022 7:21 pm
Thats an interesting question, the FoxESS BMS systems don’t as such provide a direct % figure, they give you a residual energy figure which is kind of the same thing as in it tells you what the battery capacity is when at full charge.
My batteries have nearly 300 cycles on them but in all honesty if it’s there I can’t measure any loss of capacity, I also read a paper that said ageing has as big an effect as use but again after nearly 20 months it’s not easy to see any measurable decline.
So far very happy with my choice, I was hoping for at least 10 years life and it would seem that > 15 years is likely albeit probably at around 60% of the existing capacity - so I imagine that lower capacity and new higher density battery technologies will be the main driver for any replacement.
My batteries have nearly 300 cycles on them but in all honesty if it’s there I can’t measure any loss of capacity, I also read a paper that said ageing has as big an effect as use but again after nearly 20 months it’s not easy to see any measurable decline.
So far very happy with my choice, I was hoping for at least 10 years life and it would seem that > 15 years is likely albeit probably at around 60% of the existing capacity - so I imagine that lower capacity and new higher density battery technologies will be the main driver for any replacement.
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jerryhawkins
- Posts: 14
- Joined: Wed Mar 08, 2023 6:03 pm
Thanks for your reply Dave.
I have a Solis 6kw hybrid inverter which I assumed was getting the SOH value from the FOX BMS. I wonder if it's somehow generating this SOH figure from other BMS parameters or if it's just 'guessing' based on either the number of cycles, total charge delivered since install or simply the elapsed time since install. With such a small change, it will be some years before I will be able to detect any loss of capacity in normal use. Generally my bank is discharged to between 40-50% capacity daily, but has gone down to 20% (where the inverter stops drawing from battery and takes power just from the grid) just a few times, in really cold weather when we're using a supplemental 1kw heater to stop our camper van water system freezing! On these occasions, we've hit 20% only an hour or two before our overnight cheap-rate tariff kicks in and charges the bank again.
I'm sure the SOH value won't decrease in a linear fashion, but will likely increase it's rate of decline as the batteries near their end of life. I'll have to keep an eye on this to determine the best time to replace them.
I have a Solis 6kw hybrid inverter which I assumed was getting the SOH value from the FOX BMS. I wonder if it's somehow generating this SOH figure from other BMS parameters or if it's just 'guessing' based on either the number of cycles, total charge delivered since install or simply the elapsed time since install. With such a small change, it will be some years before I will be able to detect any loss of capacity in normal use. Generally my bank is discharged to between 40-50% capacity daily, but has gone down to 20% (where the inverter stops drawing from battery and takes power just from the grid) just a few times, in really cold weather when we're using a supplemental 1kw heater to stop our camper van water system freezing! On these occasions, we've hit 20% only an hour or two before our overnight cheap-rate tariff kicks in and charges the bank again.
I'm sure the SOH value won't decrease in a linear fashion, but will likely increase it's rate of decline as the batteries near their end of life. I'll have to keep an eye on this to determine the best time to replace them.
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PrivateRyan
- Posts: 1
- Joined: Sat Sep 07, 2024 2:03 pm
I’ve had batteries for 16 months and my SOH is it 91%. I’m a bit worried by this … should I be??
In the past 8 months, they rarely go through a full cycle and I’m charging at night (octopus agile). Am I doing something wrong maybe?
In the past 8 months, they rarely go through a full cycle and I’m charging at night (octopus agile). Am I doing something wrong maybe?
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Dave Foster
- Posts: 1328
- Joined: Thu Oct 13, 2022 7:21 pm
I've heard anything from 90-94% for 18 month old batteries, so this would appear to be in the 'normal' range, but in all honesty, I don't think anyone knows what it precisely means, i've read that LFP batteries degrade faster in their first years of operation so hopefully that's what we are seeing.PrivateRyan wrote: ↑Sat Sep 07, 2024 2:06 pm I’ve had batteries for 16 months and my SOH is it 91%. I’m a bit worried by this … should I be??
In the past 8 months, they rarely go through a full cycle and I’m charging at night (octopus agile). Am I doing something wrong maybe?
Your battery warranty is based on energy throughput, they maintain a counter as to how much energy has gone through them (charge & discharge) - the warranty guarantees your batteries retain 70% of their nominal capacity after 10 years or the minimum Energy Throughput specified in the battery warranty (whichever comes first).
I have a Foxess system with 7 HV2600 batteries.
Two years old.
I had a problem in that I was getting a SOH of 77% in June.
Originally 3 V1 batteries and 4 V2
Fox have replaced the 3 V1 with 3 V2, upgraded software.
So two V2 are 12 months old, two were new in June 2024, three were replaced in August 2024. With software upgrade.
The system has cycled for the past 10 days.
SOH is still 77%
Fox have told me to wait for three months, this doesn’t seem right.
Is it that the BMS Box needs to be reset, or does the BMS only count SOH down?
Two years old.
I had a problem in that I was getting a SOH of 77% in June.
Originally 3 V1 batteries and 4 V2
Fox have replaced the 3 V1 with 3 V2, upgraded software.
So two V2 are 12 months old, two were new in June 2024, three were replaced in August 2024. With software upgrade.
The system has cycled for the past 10 days.
SOH is still 77%
Fox have told me to wait for three months, this doesn’t seem right.
Is it that the BMS Box needs to be reset, or does the BMS only count SOH down?