Storing LFP Cells for 2 Months - SOC/Voltage Recommendations

[BipedalPrimate]

Have completed individual full cycle cell testing for 16 LF280K cells which demonstrate an average capacity of 307Ah (Min 305.3, Max 308.4, SD 1.1Ah).

First full charge to 3.65v resulted in about 220Ah charged for each cell. Appears they were shipped at 21% SOC Nominal.

On completion of each cell full cycle test, cell was then discharged at 40A for 1 hour.

Doing the math suggests that cells are now at 95% SOC Nominal (267/280) or 87% SOC Measured (267/307).

Cells are now at an average Voltage of 3.332V (Min 3.329V, Max 3.335V).

Cells arrived with an average Voltage of 3.289V (Min 3.287C, Max 3.292V).

Cells will be stored in boxes & insulation they were shipped in (lots of foam padding) in partially insulated store room at 37S close to coast during Oct/Nov - do not expect low (<5C) or high (>30C) temperatures during southern hemisphere spring. (En Nino may have something to say about though.)

As I will be traveling for the next 2 months, my question is should I be concerned about the high'ish SOC or Voltage during my absence?

High'ish in this context is above recommended storage SOC (50%) which corresponds to cell Voltage of 3.25V as per discharge testing - can expect cells to rebound to approx. shipped Voltage or slightly above after discharge to that level.

 

[sunshine_eggo]

Temperature is what really triggers issues with storage at high SoC.

If in a climate controlled ~25°C ambient or less, storage for a couple months won't matter.

You can't reliably use voltage as a SoC target. Simply discharge based on current/time. If you're really paranoid, cut another 100Ah out of them to get them below 70% SoC.

 

[chrisski]

If you have time to get them to 70%, I’d do that; if not 87% will be fine. I’ve kept my RV battery at about SOC in comfortable temps for a couple of.months.

I used to travel 10 months a year and I never could get as much done as I could have when I was home so I could do something enjoyable.