Is it fine to not fully charge LifePO4 banks for extended periods?

[LifesBetterWhenYoureBeating]

Hi there,

My LifePO4 house bank has been working at around 70-95% SOC for around 2 weeks because there have been too many rainy/cloudy days so my solar panels can't fully charge them. I'm wondering if it's fine to not fully charge them for extended periods (e.g a month) or if I should make sure they get fully charged every once in a while. If the latter, how often should they be fully charged?

Thanks in advance!

[Qismat]

LiFePo4 is happiest around 50-60% - You can go without charging them to 100% for forever if you want and it will make no difference. Many people have different definitions of 100% - Some say 100% is 16.6V, others 14.2, and others still 14.6 - And only charge to these maximums.

Long story short, no, it doesn't matter one bit.

[newhaul]

Originally Posted by LifesBetterWhenYoureBeating

Hi there,

My LifePO4 house bank has been working at around 70-95% SOC for around 2 weeks because there have been too many rainy/cloudy days so my solar panels can't fully charge them. I'm wondering if it's fine to not fully charge them for extended periods (e.g a month) or if I should make sure they get fully charged every once in a while. If the latter, how often should they be fully charged?

Thanks in advance!

Heck mine are only actually charged fully one time a year when doing my capacity test.
Otherwise I charge to 13.8 or so on solar alone . Which amounts to 90% keeps me off the knees .

[SOLAR SUPPORT]

I use 2x200Ah parallel connected 12V Drop-in Lifepo4 batteries for home supply. When the capacity of the batteries is Soc 90%, the system voltage starts to rise above 13.4. Beyond that, it poses a threat to all my chargers. I set all my chargers to cut off charge above 13.5 volts. If you are going to leave the boat for a long time and there is no working device on the boat, leaving the Soc at 50-60% is the healthiest for Lifepo4 batteries. At this point, Lifepo4 and LA batteries have opposite needs.

[Adelie]

Originally Posted by LifesBetterWhenYoureBeating

Hi there,

My LifePO4 house bank has been working at around 70-95% SOC for around 2 weeks because there have been too many rainy/cloudy days so my solar panels can't fully charge them. I'm wondering if it's fine to not fully charge them for extended periods (e.g a month) or if I should make sure they get fully charged every once in a while. If the latter, how often should they be fully charged?

Thanks in advance!

My research says the PSoC operation of LiFePos is fine.

Some Li-ion battery chemistries don’t like to be fully charged. Unless they are about to be immediately discharged. Then it become a question of what do you call fully charged.

[NPCampbell]

It's my (limited) understanding that the SEI layer that protects lithium batteries has a strong dependence on cell voltage. In simplistic terms, the electrolyte in lithium batteries corrodes the surface of the anode. As the voltage increases, the rate of corrosion increases. This is one reason why lithium chemistries with lower cell voltages have higher cycle lives than those with higher cell voltages.

With LFP, the no load voltage is fairly linear from 20-90% SOC and then spikes upwards as you approach the last 10% of SOC, increasing the rate of corrosion. Keeping your battery around 70% ensures you stay out of the higher voltage range while maximizing the shelf life due to self-discharge.

[lmxr]

Originally Posted by LifesBetterWhenYoureBeating

Hi there,

My LifePO4 house bank has been working at around 70-95% SOC for around 2 weeks because there have been too many rainy/cloudy days so my solar panels can't fully charge them. I'm wondering if it's fine to not fully charge them for extended periods (e.g a month) or if I should make sure they get fully charged every once in a while. If the latter, how often should they be fully charged?

Thanks in advance!

To avoid reduced capacity due to the memory effects, I suggest to do a full charge about every 30 partial cycles where charging went to > 80 % and was followed by a time of rest. Here you find the research paper describing the memory effect in LFP batteries.


For the rest LFP is absolutely fine with partial PSOC operation (20...80 % SOC), it even considerably extends the lifetime compared to operating at the upper end.

[goboatingnow]

Originally Posted by lmxr

To avoid reduced capacity due to the memory effects, I suggest to do a full charge about every 30 partial cycles where charging went to > 80 % and was followed by a time of rest. Here you find the research paper describing the memory effect in LFP batteries.


For the rest LFP is absolutely fine with partial PSOC operation (20...80 % SOC), it even considerably extends the lifetime compared to operating at the upper end.

Memory effect in LiFePO4 is peculiar and can occur within one cycle and is best erased by full charge

https://www.tytlabs.co.jp/en/review/..._057sasaki.pdf

Oops sorry just released we both referenced the same paper

[Rumrace]

My Tesla is near 6 years old and always charges itself to 80% then creeps up to 100. It’s not recommended to give the system partial charges. The charging system is intuitive enough not to cook itself.
Leaving lithium on charge or charging at a higher mA will cause more damage than not charging.
Most laptops fry out because they are left plugged in.
A good lithium system acts more like a capacitor than a battery