Advice on LiFePo4 bank storage

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Re: Advice on LiFePo4 bank storage

Postby saltydawg » Wed Nov 24, 2021 11:16 pm

John61CT wrote:Far from authoritative source.

Actual numbers vary by the specific chemistry.

For LFP at the standard 25°C

0.4C or lower is best for longevity.

Many care more for saving time, say an EV scenario, happy to sacrifice life cycles, go up to 1C or even faster.

In racing, preheating cells to 90°C is common in order to make 3+ C-rates somewhat safe, but they are buying new packs ever season.

In sweater weather, no pre-heating I'd stick to 0.2C or slower.

Anywhere near freezing I would bring inside or do pre-heating.

I would like to see your source, battle born batteries wont charge or discharge over 135-140 or so degrees F, or about 57 degrees. their BMS wont allow it, if heating them to 90 C or 194 F helps them charge then why is one of the biggest makers making their batteries shut down at 134-140 degrees. The standard for almost everything is 25C or 77F, why because that normal room temp range. Again link at bottom says dont charge at high temp.

Do you really think Tesla would set their chargers to charge faster than the batteries can handle and loose capacity when they are warranting the batteries for many thousands of miles. Now granted tesla uses li ion not lifepo4. Even battle born says up to 1 c is fine, but .5c is preferred for longevity.

I do agree if close to freezing, bring inside or warm it up. Standbuy loss on a lifepo4 is about 2% amonth, so a battery at 75% stored for a year would be about 50% at the end of the year.

A few authoritative sources ... mperatures
Last edited by saltydawg on Wed Nov 24, 2021 11:25 pm, edited 1 time in total.
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Re: Advice on LiFePo4 bank storage

Postby John61CT » Wed Nov 24, 2021 11:20 pm

Good post for cross fertilization

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Re: Advice on LiFePo4 bank storage

Postby John61CT » Wed Nov 24, 2021 11:49 pm

Again, Battery University may be a good 101-level learning resource for e.g. general principles, noobs learning terminology but full of errors, over-generalizations etc

Also, I have never recommended using any Drop-in units, but that's another topic. Do not extrapolate what vendors state about their finished systems to the cells themselves, or LFP chemistry in general.

Finally, Tesla does many many things that are far outside the scope of what any DIYer should consider, given their investment in proprietary monitoring & control systems, not least their incredible TMS temperature management gear.

They are also constantly changing how their various chemistries (including LFP increasingly) are managed to balance car performance, user convenience and battery longevity.


Sorry if I was not clear, pre-heating cells up to 100°F or higher is not something I am advocating people with House banks should do, just to get safer fast charging say well over 1-2C, even 3-5C, those rates are only needed in say a racing context.

But getting up above say 70°F is perfectly reasonable to optimize for longevity if you want to get your charge rate up over 0.5C.

Approaching freezing temps, I'd stay well under 0.1C, and even that IMO risks dendrite formation.
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Re: Advice on LiFePo4 bank storage

Postby cluttonfred » Thu Nov 25, 2021 2:25 am

Will Prowse puts out a lot of good info including the current best deals in terms of quality/price out there for batteries, solar panels, and other components.

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Re: Advice on LiFePo4 bank storage

Postby John61CT » Thu Nov 25, 2021 11:44 am

He certainly knows a lot more now than he did a few years ago.

Back in the day he exhibited a lot of overconfident Dunning–Kruger, put out a lot of misinformation, and was very defensive about being corrected.

Personally I never trust YouTubers and other "professional influencers" flogging product, but I realize these days that's a minority opinion.
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