Winter storage for Lithium Batteries

[Romer]

I am looking at swapping my AGM batteries for Lithium batteries (LifePRO). My only concern right now is winter storage

I have a detached non insulated garage I keep my Karavan in. In Colorado there are days (not a lot) it gets below zero sometimes (rarely) below -10F. The temp in the garage may be warmer, but not much

The battery box is in a front external compartment that is not insulated

My AGMs are always plugged in and charging and have been OK for over 4 years. They are starting to degrade, why I am making the swap now

I understand with the Lithium you dont keep charging them, especially in cold weather. You charge them and let them discharge while not in use

I see that Relion makes a LT style cold weather battery

I was looking at Battle Born, Relion and I saw the Dakota batteries which also highlight cold weather operation

Cold weather storage over the winter for my Karavan and the impacts on the new batteries are my one remaining item before pulling the trigger

I am not a winter camper, but can see some nights getting down below freezing during the spring or fall

Hopefully that defines my situation and planned usage

Battleborn makes heaters that wrap the batteries, but with that I would have to monitor the charge

I could put an electric blanket in the battery box, but nervous leaving that plugged in in my detached garage over winter

Do I take the batteries out of the Karavan for Winter storage? Do I buy the Relion LT or look more into the Dakota Batteries?

or do I just disconnect the batteries and let them sit over the winter? the stated discharge rates would still keep them above 50% over the winter months

What do others do here and is there any other considerations?

Thanks in advance

 

[luthj]

I would check with the MFG to see what the minimum storage temperature is. If your lowest temps are not below that (except for maybe 5F during an overnight low), then you can leave the batteries installed. Just discharge to 50%, and disconnect. Cold temps and lower SOC are ideal storage conditions for LFP packs.

If you will need to charge them in temps around or below freezing (other than brief overnight lows), then you may need an insulated battery box with a heating pad/thermostat. It doesn't sound like you do though.

 

[john61ct]

You won't be getting near the low temp for **storage** unless outdoors in the Arctic.

LFP does not want to be anywhere near Full while not actively in use cycling, should not be Floated in any case.

So store discharged, around 40-60% is fine.

They won't self-discharge much in cool temps, even for a decade or more.

But, you must ensure completely isolated, so don't buy any packaged system where you can't easily disconnect or replace the BMS.

If a vampire load is allowed to completely drain the cells they can be rendered scrap, or will certainly lose hundreds of lifetime cycles.

 

[Romer]

All the batteries I am looking at have an integrated BMS. Ill have to look into that

 

[luthj]

Ideally the MFG will supply the self discharge rate (BMS and internal to cells). It may only be 10% per year, or it could be 20% per year. So adjust your storage SOC accordingly.

 

[john61ct]

All the batteries I am looking at have an integrated BMS.

Then ask them how their BMS can be disabled for long term storage.

Otherwise you'll need to visit regularly to verify the discharge rate, how often to replenish to keep at steady state in that mid-SoC range.

And maybe increase to that 60-70% range instead to buy a longer interval.

Do NOT allow to get anywhere near 3.0Vpc.

Personally I'd avoid that type of unit, lots of reasons. Integrated is fine but inaccessible not.

 

[Romer]

I talked to BattleBorn

They told me to winterize you fully charge and then disconnect all loads. It will be fine down to -4 deg F and lower for shorter periods. Battery is rated to -4 deg to +135 deg F for storage

They said there is no issue with the BMS at cold

 

[luthj]

I still would discharge to 70% SOC minimum. Its not gonna hurt anything, and its going to improve the life of the pack. Remember that BB also suggests charging to 14.6V and holding for a while, which is also not optimal for life.

 

[Romer]

Thanks I read other battery manufacturers suggesting similar to what you posted

 

[john61ct]

You **definitely** should not be charging in freezing cold regardless what any maker / vendor / industry source tells you. Check back here for specific C-rates vs temperatures.

Isolated storage in very cold is fine, as is very low C-rate discharge.

And if you don't mind a shortened lifespan go ahead and follow that "charge overly Full and let them sit like that" advice.

Since you can't disconnect their BMS that will indeed give the longest "sit without recharging again" interval.

BB only cares that you get to the end of their 10-yr warranty period, after that they prefer you buy another

You will still need to check the discharge rate and top up according to that as discussed above.

 

[Rando]

Most solid state BMS without bluetooth draw < 100uA of quiescent current. The one in the battle born appears to be a fairly generic Chinese BMS, so I assume it is in the same ball park. BMS consumption is on the order of 100mAh a month - not something to worry about.

 

[john61ct]

Trust but verify.

Start weekly, then monthly, then quarterly. . .

 

[dreadlocks]

I just park it, turn a few lights on and let it drain to my 20% SOC Cutoff.. if we get some warm days I'll go plug it in and let it charge back up, then the lights will slowly pull it back down to cut off.. thats mostly to give it a few cycles over the winter and ensure SOC keeps calibrated.. once or twice a month or so I'll login w/my Victron app from my bedroom and check on it make sure nothings gone wrong and everything looks good.