Long term storage effects on battery

[Paulie68]

We have a 2021 ZS EV. We're planning to go away for a year and just looking at our options for the car. I was curious what you ended up doing to store yours for 6 months, how it turned out and shutting your suggest doing differently?

Thanks!

My current thinking based on long term lithium storage would be to discharge to 40% SOC, then disconnect the 12V battery negative to isolate the main battery from any parasitic drain. I'd expect it to be showing around 38% to 39% SOC when powered up after 1 year or so.

Then remove and fully charge the 12V battery. Stored in a cool, dry place, this may well then be fine for 12 months, but you could attach a smart, maintenance charger to it. No great financial loss here though if you ended up needing a new 12V.

Found one post from 2020 on Speak EV forum:
BarryH
255 posts · Joined 2019

#12 · May 15, 2020

"Lithium ion battery cell chemistry if not used and stored ie the car is parked up for a substantial time should be at half charge state so that the Cathode and Anode are protected. In practice, since HV battery will slowly discharge, charging to 60 % SOC would be ideal so thereby allowing for self-discharge to 50% or just below over time. Depending on how the low voltage 12v electronics are managed the HV Battery may periodically be used to power the DC-DC Converter to top up the 12v battery. Tesla's for instance do this quite often and the HV will loose about 1% per day. MG ZS I believe doesn't fire up the DC-DC Converter automatically when stored and it is activated only when car in READY state. Potential therefore the 12volt battery can run down. You could consider connecting a solar top-up charger if car parked for very long periods, although since the UK models don't have the App and live connection, which is found on Asian model, battery drain should be less significant."

There is in reality almost zero self discharge on healthy lithium batteries stored long term at around 40% to 50% SOC. Maybe about 1% per year. This is, of course, assuming the battery is completely isolated to avoid any parasitic loads.

 

[JohnV6]

You either need the car on axle stands or have wheel protectors to stop flat spots on your tyres.
Can you not get someone to run it & move it every month and put the battery conditioner on?

I know for classic cars there are companies that store cars for rich collectors in a ready state.

 

[Paulie68]

You either need the car on axle stands or have wheel protectors to stop flat spots on your tyres.
Can you not get someone to run it & move it every month and put the battery conditioner on?

I know for classic cars there are companies that store cars for rich collectors in a ready state.

Whilst I don't dis-agree, I'm not sure how much of a problem flat spots really are. I've had a few cars over the years that have been stored for periods of several years and never lifted the wheels on them, or had any issues with tyres.

 

[Lizibee]

In the recent snowy weather I couldn't move my MG4 for a week.
My 12V battery died and I could only get into the car using the manual part of the key.
I replaced the battery with a better one and all was well.