Resting battery before charge?

[sonic88]

Thank you for finding that. I knew I had read this somewhere but couldn’t find it for the life of me.



One point, “scheduled charging” and starting to charge 3 hours after end of drive at low SoC is clearly referring to home AC charging and the “slow” rates associated with that. There’s no scheduling a charge at a supercharger...

I guess this practice is also ideal to allow the car sleep within that period - with a view of allowing the car to take voltage readings at the low soc for better BMS accuracies.

My only concern with this practice was letting the car sit when its at a very low soc (5-10%) for a few hours.
There appears to be some views that you should not let it sit at these soc's for any amount of time, and ensure you get the battery back up to atleast 20%>.
Any thoughts on this? Or is 3 hours really no big deal at 5-10% before charging back up on AC at home?

Cheers

 

[Candleflame]

I don't believe that one bit. The max at home charging speed is 11kw. If you are on a road trip and you stop at a super charger, you get 50kw-250kw. Now you're telling that a little slow 11kw charge at home is going to damage the battery? Really? You think that the battery get "too hot" from a normal drive? You think that the car has no way to regulate the temperature of the battery while driving to keep it at a good temp?

11kw is reasonably heat inducing, it causes raughly the same temperature as driving at 80kmh.

I guess this practice is also ideal to allow the car sleep within that period - with a view of allowing the car to take voltage readings at the low soc for better BMS accuracies.

My only concern with this practice was letting the car sit when its at a very low soc (5-10%) for a few hours.
There appears to be some views that you should not let it sit at these soc's for any amount of time, and ensure you get the battery back up to atleast 20%>.
Any thoughts on this? Or is 3 hours really no big deal at 5-10% before charging back up on AC at home?

Cheers

the OVC reading is at best a theory after some guys got some range back after letting the car sit at certain %. The same trick doesnt work for a lot of other people. There isnt really much evidence that the car needs to sit at anything but 90%.

We dont have much evidence that sitting at low SOC is harmful for the battery. Tesla recommends against that practice but equally a lot of manufacturers actually recommend storing their lithium ion cells completely discharged at sub 0C.
I would guess that the battery is least stressed at around 40-50%, however I couldnt really find any data for capacity loss when stored at below 40% though I suspect it is going to be less than when sitting at 90%....

 

[Zoomit]

My only concern with this practice was letting the car sit when its at a very low soc (5-10%) for a few hours.
There appears to be some views that you should not let it sit at these soc's for any amount of time, and ensure you get the battery back up to atleast 20%>.
Any thoughts on this? Or is 3 hours really no big deal at 5-10% before charging back up on AC at home?

We dont have much evidence that sitting at low SOC is harmful for the battery. Tesla recommends against that practice but equally a lot of manufacturers actually recommend storing their lithium ion cells completely discharged at sub 0C.
I would guess that the battery is least stressed at around 40-50%, however I couldnt really find any data for capacity loss when stored at below 40% though I suspect it is going to be less than when sitting at 90%....

I keep going back to the pack storage guidance Tesla provides in the EPA applications:

“To maintain service life, the battery pack should be stored at a state of charge (SOC) of 15% to 50%.”

Here’s some data that shows a significant difference in Li-ion battery capacity retention when stored at 15% verses 90%.

Ref: https://res.mdpi.com/d_attachment/applsci/applsci-08-01825/article_deploy/applsci-08-01825-v2.pdf

The bottomline is that no one should be overly concerned about the battery being at low SOC for a few hours. It is not necessary to immediately charge it above 20% for battery health.

 

[Uncle Paul]

If you are traveling and using the Supercharger system, faster charging is usually the prime objective.

If you are arriving at home, no damage will be done by waiting a bit befrore plugging in.

These battery packs are more robust than originally thought.

 

[Zoomit]

If you are arriving at home, no damage will be done by waiting a bit befrore plugging in.

Again, I’d be more concerned about charging it up and letting it sit at 90% than just leaving it at 10%, especially in the summer.

But to be clear, it’s not a question of “damage” as much as having a slightly higher but still very, very low degradation rate.

 

[Candleflame]

I keep going back to the pack storage guidance Tesla provides in the EPA applications:

“To maintain service life, the battery pack should be stored at a state of charge (SOC) of 15% to 50%.”

Here’s some data that shows a significant difference in Li-ion battery capacity retention when stored at 15% verses 90%.

View attachment 607362
Ref: https://res.mdpi.com/d_attachment/applsci/applsci-08-01825/article_deploy/applsci-08-01825-v2.pdf

The bottomline is that no one should be overly concerned about the battery being at low SOC for a few hours. It is not necessary to immediately charge it above 20% for battery health.

so again, this is very reasurring.
It's also the reason why I would recommend not to charge to 90% if you live in Australia/Africa/southUSA.
It gets very hot here and the battery only gets cooled if its above 30 degrees (or maybe even 35 degrees), unless when its charging where AFAIK the battery gets cooled to be below 25 degrees.

We dont know what additives Tesla puts in their lithium ion batteries. I suspect that their batteries store better at higher SOC as evidence by the lack of degradation from people charging to 90% (which is true 85%) in Taxas summer all the time - clearly not as detrimental as your graph suggests.

i would also think that 90% is bad, but 80% is probably not much worse than 50% and 50% only slightly worse than i.e. 30%.