Li-Ion GEM Winterization / Cold Storage


This is my first post here. I’m a proud new owner of a 2021 GEM 8.9 kwh Li-Ion, and while I’ve seen loads on Li-Ion conversions, I haven’t seen much on (OEM) Li-ion storage in these forums. Much of the GEM literature says to keep the batteries and charger plugged in and fully charged if being garaged for long periods, but I do not believe that pertains to Li-Ions… Most of the dealer reps I talked with hadn’t had experience with Li-Ions either. so they weren’t much help. Unfortunately, I only have a few weekends here in Northern Michigan before I have to store them, so I’m looking for some quick winterization tips.

My current plan for the car is to get a cover off amazon and hopefully find a friends garage to cold store the car in (although it will likely end up parking under a deck). It sounds like blocking the tires and disengaging the e-brake will help keep the cable from stretching. I’m also looking for an oversized cover to sticker it to the ground and hopefully keep out the animals. They are relentless up here, so I may end up taking out the seats to keep them from being chewed up. Any good cover brands out there?

My plan for the battery pack is to run it down to 40%, disconnect it, remove it, and store it in a cold (20F-40F) basement to prevent them from temperature cycling.

From what I’ve researched, it sounds like the batteries like to be stored cold at about a 40% charge:

I have no plan to connect a charger with these, as it seems like the discharge rate will only be 1%-2% per month. Keeping them between 20% and 40% appears to be the way to go. I’m assuming they will not self heat if they are disconnected from the BMS and should store fine.

I’m also curious if there is a procedure to safely disconnect the batteries. I have a linemen friend with insolated gloves, but would prefer to keep arcing to a minimum… there is supposedly a service disconnect, but I haven’t been able to locate this yet. I’m guessing the process is something like this:

  1. Remove service disconnect
  2. Disconnect negative lead to 12 volt battery
  3. Disconnect positive lead to 12 volt battery
  4. Disconnect negative lead from Li-Ion
  5. Disconnect positive lead from Li-Ion
  6. Unplug pinout cords from Li-Ion

Does this sound good? Am I crazy? Should I bury the batteries to extend the life? Should I put them in my freezer!? Any tips are greatly appreciated.

Thanks in advance!

like your plan but imho i wouldn’t bother pulling them out . Lithium does not like to be charged when cold but i have never heard of a problem cold storing them .

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I agree, leave them in place. At a charge state less than 100% and never recharge when cold. Better BMS’s have cold temp lockout. But you have no reason to recharge and find out.