Long term storage of Lithium Phosphate batteries

[SomebodyInGNV]

Just noticed that Battleborn recommends charging to 100% and then disconnecting for long term storage...

Hmm... That makes it easy. I'll just leave the SCC on and turn it off after a day or so.

 

[solartomboy]

Sorry to bump old thread. I want to find some facts on whether to store LiFePO4 batteries at 100%, or at 50%, I can’t seem to find concrete information.

 

[harpo]

Well, it has been a while since my original post. Sense then I have put a LifePO4 battery system using all Victron supporting components. I assembled the battery with cells purchased from Amy and used an Overkill BMS. The system has worked beyond my expectations during the warmer and transition months. But, as explained in my original post, I leave the cabin for approximately four winter months when the temperature will consistently be below freezing and, at times, below zero F.
I did a lot of research since my original post and got some outstanding data from individuals who work with LifePO4 chemistry. After all this I sensed a consensus concerning long term storage in cold weather. So, I took the chance and left my battery at the cabin for the winter. I reduced the charge to 55% and disconnected all loads and the charge controllers were turned off. Nothing in and nothing out.
I will let you know how things turn out in May. I actually think the battery will be fine but don't know this for sure. Stay tuned.

 

[CptPat]

I have 650 amp-hours of LiFePO4 batteries in a 12 volt bus on my sailboat. The batteries have been in storage for four years, and my last capacity test conducted a year ago showed a 2% loss of capacity (they originally tested at about 2% above rated capacity, so now they are at factory spec.).

I'm using a Victron IP43 12 | 50 charger. I depend on the batteries to provide power during power outages to maintain telemetry and an amateur radio repeater for community emergency comms, so I want to maintain some storage charge. I charge to 14.2 volts after a power outage with a tail current charge cutoff of 12.5 amps. Those settings achieve very near a 100% SOC. House loads on the bus then draw the batteries down to the charger's set storage voltage, which I have set at 13.16 volts (3.29 volts per cell). Using my Victron smartshunt as a coulomb counter, that voltage equals a SOC of 66%. My installation environment is nearly ideal with the temperature never going below 9 degrees C nor above 27 degrees C.

My analysis of calendar aging versus storage voltage from research literature indicates a "stepwise smooth" curve form, where the aging accelerates with SOCs above 70%, so my goal is to stay below that SOC.

 

[sunsurfer]

I have been reading up on these batteries because I want to replace my AGM's at the cabin (remote cold winter location). Wil recently reviewed a BMS with a low temperature cut off that actually works which is one concern I had. (I want to build my own battery). Another concern I had was long term storage. This was not much of a concern because I thought Wil indicated these batteries don't degrade as fast as a lead acid variety. Then I read on one solar site that these batteries should not be stored at full charge but something much less and, in the same light, they should not be subject to a float charge which, of course, is designed to keep the battery at full charge. I have only seen this information on this one particular site so I don't know if this is accurate or not. Anyone care to comment or have references to support or refute this information?

how long of storage are you talking?

Biggest concern would be a micro draw from say a SCC or BMS. There is an article on an LFP bank in a motorhome that was destroyed from the BMS drawing it ALL the way down from a tiny LED that was on.

How about any self discharge?

 

[Supervstech]

how long of storage are you talking?

Biggest concern would be a micro draw from say a SCC or BMS. There is an article on an LFP bank in a motorhome that was destroyed from the BMS drawing it ALL the way down from a tiny LED that was on.

How about any self discharge?

That system was parked in storage away from any solar input, and no charging was attached.
For two years, if i recall.
Dont do that.
Full float is unwise long term, but a storage float at say 3.2V per cell should keep the cells from around 50% charge, without getting them close to full which would degrade them.