LiFePO4 - how far to drain

MEN! said:

Hi guys,

I have two 12v 200Ah batteries in parallel for a 400Ah bank. I was just wondering (1) what is good practice for draining lithium batteries? I have read it is not (2) great practice to leave them sitting at 100% SOC for long periods of time. (3) Should I be constantly draining them and recharging? And what would be a (4) 'good' percentage to drain them to each time?

Thank you

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snoobler said:

(1) it varies on the cell quality. Low resistance, high quality cells don't really matter a lot.

(2) LFP doesn't degrade with high SoC storage as much as Lithium NMC, but it's possible. Battle Born indicates their batteries can be stored at 100% indefinitely.

(3) In most cases, when people use them semi-regularly, that's what happens and that's all that's needed. Rather than deliberately cycle them for no reason, the more conservative approach is to store them at a lower state of charge.

(4) Most new cells received are somewhere around the 3.25-3.3V range. Draining a know amount down to 50-70% of capacity should be fine.

If storage time is a few months, it's probably not an issue. If you're talking years or indefinitely, you likely want to store them at a lower SoC.

Temperature is also a major player. If they're stored indoors in a controlled environment or in cool but not exceedingly cold weather, very little degradation will occur. Hot temps accelerate degradation.

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snoobler said:

Not at all. 50% drain rule is only true for lead-acid. LFP can go to 0%, but 20% is recommended to further improve cycle life as is charging to a little less than full. Operating in the 20-80% SoC range may substantially improve the cycle life.

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MEN! said:

Thank you. Mine are in a full time van conversion and will be used daily. Will damage occur if I am regularly draining beneath 50%?

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How to Find Happiness With LiFePO4 (Lithium-Ion) Batteries – Solacity

By: Rob Beckers You have just sold your first-born into slavery, remortgaged the house, and bought yourself a lithium-ion battery! Now you want to know how to take care of your precious new purchase: How to best charge lithium-iron batteries, how to discharge them, and how to get the maximum...

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MBR said:

Dunno how you actually bought LFP but are asking such questions. Did you read anything on LFP batteries?

How to Find Happiness With LiFePO4 (Lithium-Ion) Batteries – Solacity

By: Rob Beckers You have just sold your first-born into slavery, remortgaged the house, and bought yourself a lithium-ion battery! Now you want to know how to take care of your precious new purchase: How to best charge lithium-iron batteries, how to discharge them, and how to get the maximum...

www.solacity.com

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