Optimal compromise for LiFEPo4

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Academic

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What is the optimal state of charge to cycle on for a LiFePo4 battery please? Compromise between utilizing as many solar generated power units as possible and battery longevity. If load shedding looms then I manually adjust it upwards as risk mitigation.

I am playing between 40% and 50% and struggling to make my mind up.
 
Academic said:
What is the optimal state of charge to cycle on for a LiFePo4 battery please? Compromise between utilizing as many solar generated power units as possible and battery longevity. If load shedding looms then I manually adjust it upwards as risk mitigation.

I am playing between 40% and 50% and struggling to make my mind up.
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Depends entirely on your battery's specs. I used to take mine down below 20%
 
Academic said:
What is the optimal state of charge to cycle on for a LiFePo4 battery please? Compromise between utilizing as many solar generated power units as possible and battery longevity. If load shedding looms then I manually adjust it upwards as risk mitigation.

I am playing between 40% and 50% and struggling to make my mind up.
Click to expand...
LFP likes to be at 50%. It doesn't like high or low SOC. If it was me I would keep it at 50%, then when loadshedding forecast gets gloomy, up it to 100%, then when it's over, go back to 50%. If you want to cycle daily, I would go in the 20-80% range.
 
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wingnut771 said:
LFP likes to be at 50%. It doesn't like high or low SOC. If it was me I would keep it at 50%, then when loadshedding forecast gets gloomy, up it to 100%, then when it's over, go back to 50%. If you want to cycle daily, I would go in the 20-80% range.
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And my battery manufacturer recommended regular cycling from 0 to 100 to ensure the bms remained calibrated correctly...
 
Sinbad said:
And my battery manufacturer recommended regular cycling from 0 to 100 to ensure the bms remained calibrated correctly...
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I often wonder what the actual difference between a LFP cell that can go to 0 and another LFP cell that only goes to 10 or 20? I know yours are BYD cells.

IMHO, I don't think there is a difference, it's just marketing, BYD cells rated at 3000 cycles but can go to 0 compared to pylontech cells rated at 6000 cycles but at 5-20% SOC. I'm sure if one could take pylontech to 0, it too would last 3000 cycles.
 
wingnut771 said:
I often wonder what the actual difference between a LFP cell that can go to 0 and another LFP cell that only goes to 10 or 20? I know yours are BYD cells.

IMHO, I don't think there is a difference, it's just marketing, BYD cells rated at 3000 cycles but can go to 0 compared to pylontech cells rated at 6000 cycles but at 5-20% SOC. I'm sure if one could take pylontech to 0, it too would last 3000 cycles.
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The BYD age is measured in charge in and out. You can cycle it from 80% soc to 100%soc 5 times and the internal counter will basically record that as one cycle. Their warranty is actually based on physical energy in and out, not cycles.
 
Sinbad said:
The BYD age is measured in charge in and out. You can cycle it from 80% soc to 100%soc 5 times and the internal counter will basically record that as one cycle. Their warranty is actually based on physical energy in and out, not cycles.
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Yes, but it's only 3000 cycles, why not 6000? If they changed their model and only made it go to 20% SOC then they could boast it doing 6000 cycles.
 
wingnut771 said:
Yes, but it's only 3000 cycles, why not 6000? If they changed their model and only made it go to 20% SOC then they could boast it doing 6000 cycles.
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Mine was basically 10 years warranty at a full cycle per day - and guaranteed 70% usable capacity at that point.
 
wingnut771 said:
LFP likes to be at 50%. It doesn't like high or low SOC. If it was me I would keep it at 50%, then when loadshedding forecast gets gloomy, up it to 100%, then when it's over, go back to 50%. If you want to cycle daily, I would go in the 20-80% range.
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This kind of info is inaccurate in current times.

You forgot about the BMS in recent lithium batteries ?

anyway , in 9 years time I will revert with my experience , where my setup on a 28kWh bank is set to discharge up to 60% on daily cycle and charge full to 100% .

when grid power is lost, battery is allowed to discharge up to 85% of capacity.
 
The_Traveller said:
This kind of info is inaccurate in current times.

You forgot about the BMS in recent lithium batteries ?

anyway , in 9 years time I will revert with my experience , where my setup on a 28kWh bank is set to discharge up to 60% on daily cycle and charge full to 100% .

when grid power is lost, battery is allowed to discharge up to 85% of capacity.
Click to expand...
Why is it when you get a new LFP battery it's only at 50% charge and not 100%? It's because 100% SOC shortens their life when just being stored. Cycle life increases exponentially if one keeps out of the very top and very bottom of SOC. Obviously this is counter productive in electric cars due to range but if they did, the battery would last the life of the car instead of needing replacement after 10 years, but one can always get more batteries for the house to accommodate for this. AFAIK, BMS limit cells to 3.65V which is their limit anyway. By just changing voltage to 3.5V per cell for example will improve lifespan considerably IMHO.
 
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