Why temperature of lithium cells is important

Why temperature of lithium cells is important 2

Temperature is an important parameter that influences the aging of a lithium battery. At 35°C a lithium cell ages twice as fast as it does at 15°C. So if the battery’s useful life is 15 years at 15°C, it will be 7.5 years at 35°C.

I summarize some research results and draw guidelines to better manage our lithium cells (LiFePo4) for a longer life. I also explain how the features of the TAO BMS can help.
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Philtao
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Pretty Clear, would like degrees F with C or a little chart at the end. The point about storing at 50%C is interesting.
Thanks for keeping this simple but not skipping the fundamental distinction between "calendar aging" and "cycle capacity loss". I was aware of both but not in a way that would have allowed me to distinguish between the two as you have done. I was also not aware that the cycle capacity loss was lowest at 35 degC while aging was twice as fast compared to 25degC.
I like the multi-dimensional table although I'm not convinced a graphic might not have been better. One thing that still confuses me is what does SOC means on the left column. Is this cyclic depth of discharge?
Philtao
Philtao
Thanks for the feedback. Good idea for the graph - it will require 3 graphs as a single 3D graph will be confusing. I will try and post an update if I can get something meaningful.

SOC corresponds to the average State Of Charge of the cells. It has an important impact for calendar ageing.
For example cycling the battery regularly between 60% and 100% soc would roughly correspond to an average soc of 80 %. That's why it is better to cycle the battery through its full capacity (within reason!) to lower the average soc when the installation is in full use (absolutely avoid float).
When the installation is in "storage mode" for a long time with low power usage (example: only a fridge and some safety equipment / lighting) it is better to cycle between for example 30% and 60% soc and do a full charge every 30 to 45 days (that's where an intelligent BMS can help ;-), but lowering the voltage of the solar regulator (13.2v?) will also avoid keeping the battery full all the time - it will just do micro charges every day and I do not know if that is good or not? )
Good overview PDF of Calendar Aging vs Cycle Aging. Addresses different strategies for a few climates/use cases. Temperature, SOC, are emphasized as factors in battery degradation. Useful resource that highlights the benefits of thermally managing your cells.
Philtao
Philtao
Thanks for the feedback. It feels good to know that the time and effort to prepare this is useful to others.
I appreciate the info, but I don't love how the "download" is just a link to your personal website where you promote your wares for sale. This site would be awful if more companies were adding links and generating "content" this way.
This helpful 'resource' which promises to present info about how to extend the life of your batteries does so by telling you how the TaoBMS system's features can do the job. This kind of seems like an undercover advertisement.
Philtao
Philtao
I agree with you that I failed to set the reader's expectations properly. I have edited the description to make it clear that I also explain how the features of the BMS can help extend the life of a battery (I think there are only 3 highlighted sentences that mention the BMS).
I will also replace the link with a PDF. Thanks for the feedback, we are all learning...
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