Storing LiFePO4 batteries long term and other subjects

[No cats]

So, I've been doing a lot of reading and researching what state of charge a LiFePO4 battery should be in for storage. As an electrical engineer, I've looked for real research and data, but there is very little of that available. I personally, store min LiTime fully charged and disconnected from the RV.

While searching, I found this video from Will Prowse. In this video, Will interviews Battleborn CEO regarding many of the hot subjects in this forum. From low temp charging/discharging (first 6 minutes), high temp usage, charge profile, balancing , floating the batteries and lastly, long storage (minute 15 on).

The CEO while talking about his batteries also generalizes to all LiFePO4 chemistry batteries for much of the video. When asked by Will about SOC for storage, the CEO recommends to store at full charge.

 

[DonTom]

So, I've been doing a lot of reading and researching what state of charge a LiFePO4 battery should be in for storage. As an electrical engineer, I've looked for real research and data, but there is very little of that available. I personally, store min LiTime fully charged and disconnected from the RV.

While searching, I found this video from Will Prowse. In this video, Will interviews Battleborn CEO regarding many of the hot subjects in this forum. From low temp charging/discharging (first 6 minutes), high temp usage, charge profile, balancing , floating the batteries and lastly, long storage (minute 15 on).

The CEO while talking about his batteries also generalizes to all LiFePO4 chemistry batteries for much of the video. When asked by Will about SOC for storage, the CEO recommends to store at full charge.

Welcome back! It was nice to meet you in person here.

They do not all use the same cells. Some should be left charged at 60%, others 80% and some at 100% SOC. With my Ampertime 300 AH Lifep04 batteries, it came with a pamphlet. It explained my 300 AH battery was built in a 200AH case, so it is smaller but heavier because of the type of cells used. And it also explained mine is best stored at 100% SOC-unlike perhaps most.

So if a pamphlet came with your battery, be sure to read it. It should explain how it is best stored. Do not assume they are all the same.

FWIW, I do not think it is that critical. It was probably just to improve the odds of getting past the warranty. My guess (but not based on much more!) is that anything above 60% SOC is fine for storage with any of them. Perhaps will last a few months longer of the exact instructions are followed, but now that LIfep04 batteries are so cheap, it's just not a big deal to get the last few hours out of them.

FWIW, Zero electric motorcycles should be stored at 60% SOC. My Energicas should be stored at 85% SOC. Again, different types of cells are used. Only go by what the manufacturer recommends for your battery and even that can change from one of their designs to the next--such as with Ampertime.

-Don- Q., AZ

 

[No cats]

Thank you, It was nice to meet you and the others at Quartzsite.

I have LiTime batteries, two 100Ah. Nothing came with my batteries regarding the SOC for storage. I have been trying to digest this whole subject so as to not have to put a load on my batteries (to discharge them) prior to storage. I agree that it's probably optimum to store them at between 50 and 80%.

 

[DonTom]

Thank you, It was nice to meet you and the others at Quartzsite.

I have LiTime batteries, two 100Ah. Nothing came with my batteries regarding the SOC for storage. I have been trying to digest this whole subject so as to not have to put a load on my batteries (to discharge them) prior to storage. I agree that it's probably optimum to store them at between 50 and 80%.

---

A web search shows:

"It is recommended to store LiTime LiFePO4 batteries at 50% state of charge (SOC). If the batteries are stored for long periods, cycle the batteries at least every 6 months. Recommended storage environment: 10℃～35℃ (50℉～95℉), 45%RH～75％RH"

RH: Relative Humidity.

But no link was given for this search.

It is less hassle to have batteries that should be stored at 100% SOC such as my 300-AH Ampertime batteries. The solar in each of my motorhomes takes care of it all for me. I never remove the batteries.

-Don- Q., AZ

 

[No cats]

Ampere Time's website says to store at 50% and yet they sent you instructions to store at 100%. It is not clear to me that manufacturers have a common standard for rating capacity degradation based on storage time and SOC. Seems to me that heat is the worst enemy of the LiFePO4 batteries as far as capacity degradation is concerened.

 

[DonTom]

Ampere Time's website says to store at 50% and yet they sent you instructions to store at 100%.

Yes, because my Ampertime was different than most other Amertimes, because it uses a different & heavier cell so they could make the battery smaller than normal. Their 200AH & 300AH battery is the EXACT same physical size--put in the same case, but the 300AH is a lot heavier than their 200 AH. IOW, same make, much different type of cell and therefore much different storage instructions.

-Don- Q., AZ

 

[DonTom]

Seems to me that heat is the worst enemy of the LiFePO4 batteries as far as capacity degradation is concerened.

Especially when left fully charged in the heat--at least on some batteries--hopefully that does not include mine which is supposed to be stored at 100% SOC.

But I assume that 100% SOC is not a true 100% SOC with Lifep04 batteries--as with EV batteries. There is a useable (nominal) capacity and a maximum (normally unusable above the nominal capacity--but not always).

For an example, if I press a switch while my Zero DSR/X motorcycle while charging, it will charge to 110% SOC and will display as 110% SOC when fully charged. Not to be used often and also to be used right away so it gets back down below 100% SOC ASAP. The default is 100% max charging and still best if not charged above 80% SOC indicated. And even the 110% is not the true max. There is another ~10% unusable above that.

I hear the EV motorcycles sold to the military can be used below zero % SOC by a similar switch. If ran down to true zero, throw the battery away! But it could save a life. All EVs (AFAIK) can go below 0% SOC and even when the car / bike stops with no juice, you're still not truly near no charge left and it can still be recharged. At true zero, the battery cannot be charged, but the BMS won't let that happen. All goes dead before then. But still needs to be recharged ASAP. With many (all?) EV batteries when the car is that dead, it much be recharged within 24 hours or else the battery warranty is void.

I am not real sure if all this applies to Lifep04 batteries, but I assume it probably does.

I know more about EV batteries than our RV Lifep04 batteries, so I am not sure how much of all this applies, but I assume it's all the same.

Nothing came with my batteries regarding the SOC for storage.

Did you get the pamphlet shown here?

-Don- Q., AZ

 

[No cats]

I did find the storage instructions.
It is "suggested" that ideal temperature for storage is between 50F to 95F. And that for "a longer-lasting product" it is "best" to store at a 50% charge level. No warnings as to what the consequences are for storing outside the "suggested" temperature.

As a past writer of requirements for electronic systems, this seems weak. Instead of "suggestions", I would expect stronger words such as recommend or require. And for the Capacity paragraph, it is equally vague.

 

[DonTom]

I would expect stronger words such as recommend or require.

I hear in the past, there was a lot of guesswork involved on lith batteries, as not many have been around long enough to see the only results that truly count.

The only "requirement" I can recall on lith batteries (again EV batteries--the type I know better) is to not let them stay below 0% SOC for more than 24 hours --or kiss the battery warranty goodby. No such warranty requirement for anything else, such as improper battery storage, keeping it fully charged, constant supercharging, etc., etc.

So it's best to not have such things a "requirement". IMO, a "recommendation" or a "suggestion" is better. The stuff other than below 0 SOC is just recommendations or suggestions. Won't void any warranties, AFAIK.

You do get your VERY strong words about keeping a battery at 0 SOC for more than 24 hours. Thousands of dollars' worth of words.

-Don- Q., AZ

 

[No cats]

My batteries came with a 5 year warranty. This warranty covers performance under normal use and service.

No where I read, on my long term storage instructions ("suggestions"), does it state that my 5 year warranty will be void if I do not follow the "suggested" parameters.

So, if I store my batteries outside the "suggested" temperatures and with a SOC of 100%, I am not warned that my warranty will be denied. This tells me that I can do whatever I want with my batteries and I will get at least 5 years out of them. Or, I will have to invoke my warranty and deal with that!

 

[DonTom]

This tells me that I can do whatever I want with my batteries and I will get at least 5 years out of them. Or, I will have to invoke my warranty and deal with that!

Yep. I think you're likely to get 5 years regardless of how they are stored. Perhaps a few more months if you follow their suggestions. Just not a big deal, IMO, especially when the prices of these batteries keep on dropping. I assume by next year Lifepo4 batteries will be cheaper than lead acids for the same capacity. But I expect the LA batteries will be around for quite a while--at least until they make a battery that is as good or better than is L-A for temperature variations and very high current loads (such as engine starting).

-Don- Q., AZ

 

[No cats]

I bought two 100Ah LiFePO batteries Nov 2023. I charged them to 100% SOC and stored them in my garage 4 months til we took a short camping trip. Solar kept them filled up the whole time we camped. Came home and stored them 100% SOC for another 5 months before our next trip. Again, batteries at 90-100% while camping. After that, stored them at 100% for 4 months until we went to Quartzsite this year.

So the batteries have been 100% for a little over a year and after this thread, I figured I'd check their condition. I also decided to start storing them at 50% SOC, so, I built myself a cheap set up to discharge and measure SOC prior to storing them.

Before I put them at 50%, I did a capacity test by discharging the batteries to 0% SOC but I stopped at 3%. I was afraid to brick the BMS. When I disconnected the load, the batteries voltage (under a 55W load) was at 12.6V.

So, I'm thinking that my batteries are still capable of delivering 100% capacity after one year of not following the 50% rule.

This just my experience, I'm not advocating anything. Just sharing info for others that may have questions.

 

[rvlifer]

Not sure how the li time batts work. My battleborns go into shutdown mode below a certain voltage but dont brick. A simple jump start gets them going again.

the solar on our rv keeps ours at 100% all the time. I never worried about it much.

 

[DonTom]

Not sure how the li time batts work. My battleborns go into shutdown mode below a certain voltage but dont brick. A simple jump start gets them going again.

the solar on our rv keeps ours at 100% all the time. I never worried about it much.

I do not recall the cell numbers, but while most LIFEp04 batteries use prismatic cells, the BB batteries use the cylindrical cells. With the cylindrical cells, you do not have to worry about keeping them fully charged and they also do better with recovery when fully discharged.

They do their cell balancing act at the top of the charge, so it is best to keep them fully charged, even for storage. Same with my 300-AH Ampertime batteries in my two motorhomes.

-Don- Q., AZ

 

[John From Detroit]

I"m Keeping mine in the 80-90% range for the big ones 100 for the small (10 and 20 amp hr) But I frequently use those.