Cycling Degradation VS Calendar Aging w/ LiFePO4 Batteries Used for Solar Application

[OffGridForGood]

That's if you don't care about higher degradation. If you must stay >70% then keep batteries cooled 10 - 25°C but do not charge them fast below 20°C. What is safe C rate below 25°C ? That still needs to be verified.

I have read over many of the studies, but there seems to be little information between 0-degrees C and 25 degrees C.
Which seems strange since normal room temps are not so high as 25, nor so low as 0. I would expect somewhere someone looked for the 'ideal' temperature - ie to guide design of grid-scale ESS ?
My ESS -winter my lowest low is 15 degrees C and in summer my highest high is 20-degrees C - yet I have no data to guide me to "ideal" ESS temp between these narrow limits, so I just let it run and hope it is ok. At least until I see better information.

 

[HighDesertOffgrid]

I have read over many of the studies, but there seems to be little information between 0-degrees C and 25 degrees C.
Which seems strange since normal room temps are not so high as 25, nor so low as 0. I would expect somewhere someone looked for the 'ideal' temperature - ie to guide design of grid-scale ESS ?
My ESS -winter my lowest low is 15 degrees C and in summer my highest high is 20-degrees C - yet I have no data to guide me to "ideal" ESS temp between these narrow limits, so I just let it run and hope it is ok. At least until I see better information.

For good or bad, that is the nature of all scientific studies. Control all other variables and test for changes in one.
ie- Hold cells at EXACTLY 0c and charge and discharge for x amount of time or cycles at x rate. Record results against control.
The studies can give a rough approximation of real world use while you and I may have 15 different variables fluctuate daily.
We are the contributing authors with accumulated average data which will be parsed sometime in the future.

 

[OffGridForGood]

For good or bad, that is the nature of all scientific studies. Control all other variables and test for changes in one.
ie- Hold cells at EXACTLY 0c and charge and discharge for x amount of time or cycles at x rate. Record results against control.
The studies can give a rough approximation of real world use while you and I may have 15 different variables fluctuate daily.
We are the contributing authors with accumulated average data which will be parsed sometime in the future.

and yet, I am sure somewhere, a research group has been asked by a grid-scale ESS battery provider - "can you study the temperatures that are ideal for our ESS climate controls, we are capable of selecting any temperature or vary temperature by SOC to achieve maximum battery life, what should the ESS tempertures be for LFP and should the temperature change with SOC / Charge-rate to achieve max ESS life ?"
-after all if a grid scale battery is megabucks, then it would be worth the effort (cost) to study and discover the ideal temperature set points to allow minimizing cell degregation.
I am sure it has been studied, I just don't know what the results are.

 

[AntronX]

In the analyzed BESS the battery packs near the floor experience much lower temperatures in an annual average than the battery packs near the top (maximum average of 32 °C, minimum average of 23 °C). Operating in the Frequency Containment Reserve market, the annual capacity degradation differs up to 0.97% between the highest and lowest observed average temperatures. Hence, the BESS's lifetime could be extended by up to 11 years.

The impact of operating strategy and temperature in different grid applications [Gräf 2022]

 

[OffGridForGood]

Thanks

The impact of operating strategy and temperature in different grid applications [Gräf 2022]

interesting read.
May need to add a recirc fan to the ESS alcove - push warmer air from the top of the alcove to the bottom and let it circulate.
I recall @Steve_S also mentioned the various temperatures of batteries in a stack having this and other impacts during charge and discharge.
I could set a date once per year to flip the ESS - top 4 packs switch places with the bottom four packs - Inversion we will call it. Time it to coincide with the lakes flipping around here as they warm up in the Spring time - just when I get ready for Fishing...there, I will never forget !

 

[Sojourner1]

The impact of operating strategy and temperature in different grid applications [Gräf 2022]

Doing a quick read over the link doesn't really say tia. Mentions NMC batteries and a weather station 30km away and for 2nd hand batteries.

Folks on here already cry about spending more money on supposed grade A cells and trying to get a little more lemon juice from them.

Maybe one of you guys are keeping notes of your systems so in 5, 10, 15 years some real life date could be had. Or the next best chemistry receipt will come along.

Just be sensible about your charging voltages and try to stay out of the extreme temperature and maybe some will have a long use.

But it does make for good reading.

 

[HighDesertOffgrid]

Doing a quick read over the link doesn't really say tia. Mentions NMC batteries and a weather station 30km away and for 2nd hand batteries.

I noticed that as well. Phrases like "semi-emperical study", "modeled " and "assumptions" also stand out.

 

[DIYrich]

The impact of operating strategy and temperature in different grid applications [Gräf 2022]

NMC batteries.

 

[BarracudaBob]

World's Largest Sodium-ion Battery Energy Storage Project Goes Live in China

They can take the heat

 

[Will Prowse]

The impact of operating strategy and temperature in different grid applications [Gräf 2022]

Fun to read and I like the conclusion about heat management, but how did they design a system so poorly.

And it's hard to believe that such a low rate caused cycling degradation of that magnitude:


How could they tell? They said the other studies create models and they drew this conclusion from what? I can't see the whole study unfortunately

 

[OffGridForGood]

10kWh was OVER-SIZED ??? The inverter idle would be a significant portion of 10kWh/d on many systems...

 

[halexudson]

Since heat seems to be a huge factor in degradation, for those of us with un-conditioned battery storage spaces, has anyone done any expermentation on geothermal battery compartment cooling? I haven't run the calculations yet but for the fairly small temperature delta between ambient and ideal ~(10C most of the time) it would probably be less than 50 watts of dissipation at the peak heat of the day. An insulated water container to increase thermal mass might even help. I've got an old PC water cooling radiator and a big roll of PEX I could probably bury in a hole a couple feet deep. In fact I could probably put it in my conduit trench (don't tell the authorities). Seems like a lot of the threads where someone suggests this die out in the theory stage.

 

[Substrate]

I suppose another tip is that for those that are calculating system capacity and not just winging it, be sure to add 20% to your capacity needs if it fits the budget. Now you have a 40% degradation window before calendrical aging puts it outside of your initial application. (classic 80% value). Especially if you know you will be in a hot environment.

Other factors that aren't tested - surge capacity vs calendrical aging. If you bought a specific brand/model for super-high surge (trolling motor or lifting Will's car on his jack), even if pampered, will it fail the surge rating you needed 4 years down the line, BUT will it do just ok at 1C discharge? I don't know.

For all the years we all have been doing this, doesn't this almost seem like an, um, spiritual quest? Kind of like "Zen and The Art of Motorcycle Maintenance" book from way back in the day.

 

[HRTKD]

For all the years we all have been doing this, doesn't this almost seem like an, um, spiritual quest? Kind of like "Zen and The Art of Motorcycle Maintenance" book from way back in the day.

Borders on Voodoo for me.