Tesla is recommending this because LFP has a very flat discharge curve, so it is difficult to know the state of charge just from the battery voltage. In order to provide an accurate battery meter, they have to do coulomb counting (or some similar method) which keeps track of energy in and out of the battery. In theory (and to some extent, in practice), this will allow them to know exactly how much energy is left in the battery, and provide a correct "percentage or miles left" indication.
Where reality diverges from theory is the fact that it is impossible to be 100% accurate when counting coulombs. As a result, one has to reset the coulomb counter to match the state of charge of the battery every once in a while so the gauge is accurate. For LFP batteries, the easiest way to do this is to charge the batteries to 100% charge. This is a tradeoff Tesla has made between being able to have a reliable battery gauge and having a battery which lasts as long as possible. I can definitely see the reasoning behind Tesla choosing the reliable battery gauge since I think I would be pissed if I got stranded because I thought I had plenty of range left when I didn't. On Fri, Apr 26, 2024, 7:23 PM Robert <i...@avantwireless.com> wrote: > This is what Tesla is recommending for the LFP based model 3 and model Y > versions. 100% charge. VS the 80% for the other chemistries. Tesla is > also going more in on LFP solutions and the latest investor presentation > said their proprietary model "breakthrough" battery is no longer an > emphasis because third party batteries are getting cheaper than they can > make. > > On 4/26/24 1:06 PM, TJ Trout wrote: > > Storing a fully charged lithium iron phosphate (LiFePO4) battery has a > minimal impact on its lifespan. In fact, it's recommended to fully charge > LiFePO4 batteries before storing them for long periods of time. These > batteries have a low self-discharge rate, typically losing 2% of their > charge per month. However, fully charged lithium-ion batteries can be > dangerous if left unused for long periods of time. > > On Fri, Apr 26, 2024 at 12:43 PM Forrest Christian (List Account) < > li...@packetflux.com> wrote: > >> >> >> On Fri, Apr 26, 2024, 1:02 PM Ken Hohhof <khoh...@kwom.com> wrote: >> >>> And I'm still using AGM batteries while all the cool kids are using >>> LiFePO4 with BCMs, so definitely don't listen to me. >>> >> >> The more I learn about lithium batteries, the more I feel that lithium >> has relatively few advantages for standby applications. >> >> My most recent knowledge acquisition is the fact that if you want to >> shorten the life of a lithium battery the best way to do so is to keep it >> fully charged. The higher the average state of charge, the shorter the >> life of the battery, although admitted there isn't much change in lifetime >> between about 20% and 80%. But keeping them at 100% isn't great. >> >> If you want to store a lithium battery without charging, it's best to >> drop the charge below 80% then store. >> >> In a standby application you really want to keep a battery at 100% which >> shortens it's life greatly. A better choice would be to keep it at 80% >> max but then you have other issues, not to mention the fact you now have to >> buy a bigger battery array. >> -- >> AF mailing list >> AF@af.afmug.com >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> > > > -- > Thank you, > > TJ Trout > Volt Broadband > 209.480.3122 Cell > > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com >
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