Long term EV storage procedure

[SanCarlosJeff]

The last time I drove my Leaf was March 14. I charged it to 100% that day and then unplugged it. This thread got me to thinking that I should go take a look at the charge level. I was very surprised/impressed to see that the battery charge is now at 99%.

[jlv]

I personally don't know about the trickle charger. I never had 12V battery issues with my LEAF, while other people have reported lots of issues. I had an 2013 SL with the silly PV panel to top off the 12V; I'm not sure if that is why.

I heard from the current owner of my 2013 SL. He told me the 12V was low after the car sat unused (outside) for 3 weeks. But then again, it's still on the original 12V battery, presumably put into service when the car was mfg'd in December 2013.

[cpmiller15]

Ok, so:

- leaving the main battery charged at 60-80%
- with the car unplugged and
- with the 12V battery remaining connected

should technically be ok for 3 months during the summer (in Southern California)

Yes. I would suggest, though, that it be left closer to 60% than to 80%. 40-50% would be optimum, if you won't need to take it on a long trip right out of storage.

Thanks for all your help. Feeling much better about storing it now!

[Stanton]

The last time I drove my Leaf was March 14. I charged it to 100% that day and then unplugged it. This thread got me to thinking that I should go take a look at the charge level. I was very surprised/impressed to see that the battery charge is now at 99%.

That's the point: the longer your battery sits near 100%, the the more its long-term health deteriorates.
Lithium batteries are designed to "hold their charge" (that's why they work so well in our cars), but don't like to be stored at/near 100% (especially in warm environments).

[WetEV]

The last time I drove my Leaf was March 14. I charged it to 100% that day and then unplugged it. This thread got me to thinking that I should go take a look at the charge level. I was very surprised/impressed to see that the battery charge is now at 99%.

That's the point: the longer your battery sits near 100%, the the more its long-term health deteriorates.
Lithium batteries are designed to "hold their charge" (that's why they work so well in our cars), but don't like to be stored at/near 100% (especially in warm environments).

TLDR: Correct.

This source is behind a paywall. Sorry.
Also is for a different chemistry, one that might had a use for a product I might have designed. Things are strange now. Remember that different chemistries have different properties, but generally similar behavior. These results are not directly usable for a LEAF, or for any other EV. This is not an automotive battery being tested.

http://dx.doi.org/10.1016/j.jpowsour.2013.09.143

The Leaf doesn't allow for an actual 100% charge, but only about 95%. The LEAF SOC gauge reports 100% at about 95% actual capacity, to say this another way.

For the cell tested in the above source, life at storage at 50C at 100% SOC was 107 days to 80% of initial capacity.
Life at 95% true SOC (or LEAF reported 100%) was a bit less than a year. Storage lifetime increased with decreasing SOC, exceeding 4 years at 50C at low SOC. Much longer calendar life at lower temperatures for all SOCs, see Arrhenius. However directly testing them becomes a challenge.

Now how does that apply to the LEAF? This isn't an automotive battery, but the same general principal does apply. Longer life at lower SOC.
Very bad things also happen at low SOC, below about 30%, but not due to calendar losses, but rather due to cycling losses and probable Li plating.

So store the traction battery at about 40% SOC, unless you might need to do a significant drive without charging. Avoid storage above about 70%, if you can help it. Avoid discharge below 30% SOC, if you can help it. 20% SOC isn't so bad, but 10% SOC and 5% are worse.

[frontrangeleaf]

The last time I drove my Leaf was March 14. I charged it to 100% that day and then unplugged it. This thread got me to thinking that I should go take a look at the charge level. I was very surprised/impressed to see that the battery charge is now at 99%.

That's the point: the longer your battery sits near 100%, the the more its long-term health deteriorates.
Lithium batteries are designed to "hold their charge" (that's why they work so well in our cars), but don't like to be stored at/near 100% (especially in warm environments).

The Leaf doesn't allow for an actual 100% charge, but only about 95%. The LEAF SOC gauge reports 100% at about 95% actual capacity, to say this another way.

[snip] store the traction battery at about 40% SOC, unless you might need to do a significant drive without charging. Avoid storage above about 70%, if you can help it. Avoid discharge below 30%, if you can help it.

This would seem to imply that unless new battery technologies get markedly better with respect to degradation, we will eventually end up in a world where we drive around with vastly larger batteries than nominally necessary in order to preserve battery life, as costs come down. Batteries with 15-20% reserve would seem to be one solution - that's what you're effectively suggesting isn't it? Drive your car between 30 and 70% charge, i.e. use 40% of available range unless otherwise needed. We've been doing 25-75% more recently, as we've gained experience.

Looking farther forward, manufacturing economies of scale will kick in enough, and we'll just replace a worn out battery every 80k miles or something. It will be interesting to see how things shake out. But for now, it would seem that battery manufacturing capacity is lagging demand.

[WetEV]

[snip] store the traction battery at about 40% SOC, unless you might need to do a significant drive without charging. Avoid storage above about 70%, if you can help it. Avoid discharge below 30%, if you can help it.

This would seem to imply that unless new battery technologies get markedly better with respect to degradation, we will eventually end up in a world where we drive around with vastly larger batteries than nominally necessary in order to preserve battery life, as costs come down. Batteries with 15-20% reserve would seem to be one solution - that's what you're effectively suggesting isn't it? Drive your car between 30 and 70% charge, i.e. use 40% of available range unless otherwise needed. We've been doing 25-75% more recently, as we've gained experience.

Looking farther forward, manufacturing economies of scale will kick in enough, and we'll just replace a worn out battery every 80k miles or something. It will be interesting to see how things shake out. But for now, it would seem that battery manufacturing capacity is lagging demand.

Batteries have gotten markedly better, and are likely to continue to become better with respect to degradation.

25% to 75% is better than deeper cycles. Mostly you should be trying to do this or a shallower cycle for the regular driving you do to get better battery life. This was true for the early Li-ion batteries and is still true for current batteries. The shallower the cycle the better in the center of the battery capacity.

Battery manufacturing capacity is and needs to be ramping up to keep up with demand.

[WetEV]

I'd leave the battery with more SOC than that; more like 60-80% (as stated above).

Li-ion battery calendar loss is dependant on SOC. The higher the SOC, the faster the loss. Yes, even down to 10%, the lowest tested.

M. Ecker et al. / Journal of Power Sources 248 (2014)

[LeftieBiker]

I'd leave the battery with more SOC than that; more like 60-80% (as stated above).

Li-ion battery calendar loss is dependant on SOC. The higher the SOC, the faster the loss. Yes, even down to 10%, the lowest tested.

M. Ecker et al. / Journal of Power Sources 248 (2014)

This doesn't seem to apply well to the post 3/2013 Leaf packs. The Wolf and Lizard packs have little calendar loss unless charged to near 100%, and the post-Lizard 30 and 40kwh packs seem to have other issues that don't have much if anything to do with storage SOC, again as long as it isn't very high.

[jlv]

I'd leave the battery with more SOC than that; more like 60-80% (as stated above).

Li-ion battery calendar loss is dependant on SOC. The higher the SOC, the faster the loss. Yes, even down to 10%, the lowest tested.

M. Ecker et al. / Journal of Power Sources 248 (2014)

If you leave the car at 80% SOC, it isn't going to reach 10% SOC faster then if you initially left the car at 60% SOC.