Effect of SoC and Temperature on Battery Life

[SageBrush]

https://www.mdpi.com/2076-3417/8/10/1825/pdf

This is a fantastic read, study from 2018
Spoiler: sitting at high SoC in high temperatures is the quick way to cook a battery.

 

[joeriv]

url busted. Edit- Fixed

 

[SageBrush]

^^
Sorry, I am not sure how to fix the URL but if you copy and paste it into a new tab the file opens.

 

[LeftieBiker]

Try replacing the "file:" with "http:". It may work for you because you have the file on your home drive. It may not work for us because we don't already have it stored.

 

[cwerdna]

^^^
Yep. "Home" isn't a valid host name on the Internet. It needs to point a protocol like http, https or ftp and also have a valid hostname.

However, some Googling for the filename helped. Led me to:
https://www.mdpi.com/journal/applsci/special_issues/Plug_in_Hybrid_Electric_Vehicle
https://www.mdpi.com/2076-3417/8/10/1825
PDF link at the above points to https://www.mdpi.com/2076-3417/8/10/1825/pdf which triggers a d/l.

 

[SageBrush]

Try this link. For me it downloads the file to my local hard drive

https://www.mdpi.com/2076-3417/8/10/1825/pdf

 

[iPlug]

What SoC are others keeping their Leafs or other BEVs at here?

My wife drives our Leaf, will usually charge it up to 100% when it gets to 20-50% SoC. It rarely sits at 100% SoC for very long, usually driven within 12 hours after achieving such.

With our new Model 3, have read that Musk says ok to leave it at ~80% max SoC where I have also kept it max charged, but wonder if lower is better. Since I only travel <25 miles on 90%+ of days, will probably keep it around 50% SOC and max charge it right before the rare long road trips.

 

[LeftieBiker]

I rarely charge to an indicated 100%. I keep my 40kwh Leaf at 50-80%, generally. Usually around 65%.

 

[SageBrush]

With our new Model 3, have read that Musk says ok to leave it at ~80% max SoC where I have also kept it max charged, but wonder if lower is better. Since I only travel <25 miles on 90%+ of days, will probably keep it around 50% SOC and max charge it right before the rare long road trips.

I think you are doing fine.

I mostly do the same although I bumped up the charge limit to 90% a week ago to improve range calibration. I'll drop it down to 70-80% in a few weeks. As summer approaches I'll drop the charging limit further since I think the message here is to not combine high SoC with extended time at high temperature. Since I no longer use the Tesla every day it has become more important to pay attention to this issue.

 

[joeriv]

If you read the study, the conclusion:

"The final conclusion from this study is that there is a huge potential for prolonging the battery lifetime by avoiding high SOC values. Additional prolonging of the lifetime can also be reached by only charging the battery with the needed energy, using a small DOD, and to do this just before the driving. This strategic planning of the charging will limit the impact from the calendar ageing."

For those of us who use a BEV for local driving, keeping the battery at something like 30-60% SOC and charging only as much is needed to maintain this range will significantly increase battery life. It also suggests, all things being equal, the larger the battery the better.

 

[SageBrush]

If you read the study, the conclusion:

"The final conclusion from this study is that there is a huge potential for prolonging the battery lifetime by avoiding high SOC values. Additional prolonging of the lifetime can also be reached by only charging the battery with the needed energy, using a small DOD, and to do this just before the driving. This strategic planning of the charging will limit the impact from the calendar ageing."

For those of us who use a BEV for local driving, keeping the battery at something like 30-60% SOC and charging only as much is needed to maintain this range will significantly increase battery life. It also suggests, all things being equal, the larger the battery the better.

Right.

The suggestion to charge before driving is another way of saying that letting the battery stew at a high SoC is best to avoid. This is particularly true as ambient temps increase, as the data shows.

 

[TomT]

Which is why I expect the 75Kwh battery in my Tesla Model 3 to last longer than I do! <G>
I normally charge to 80% and use a very shallow DoD...

If you read the study, the conclusion:
"The final conclusion from this study is that there is a huge potential for prolonging the battery lifetime by avoiding high SOC values. Additional prolonging of the lifetime can also be reached by only charging the battery with the needed energy, using a small DOD, and to do this just before the driving. This strategic planning of the charging will limit the impact from the calendar ageing."

 

[johnlocke]

So having a large battery, charging less often, limiting DOD, and charging to less than 100% are all good things. So is keeping the battery's internal temp in a moderate range (active cooling and heating). Too bad my 30KWH leaf has too small a battery and a lack of internal cooling. Since I drive 55-75 miles daily limiting DOD doesn't work very well and I don't really have any way to reliably charge to only 90%. It would have been nice of Nissan to tell me this instead of telling me to "just charge it up every night"! Of course I might have then not bought a Leaf.

 

[baustin]

Charging to 100% is not a problem. It is required, periodically, to keep the cells balanced. It is leaving it at 100% charge for extended periods of time, especially in high temperatures, that is the problem. For those without the ability to limit charging, use a timer so that charging completes just prior to the intended departure time.

I am one of the fortunate ones with a 2013 Leaf. I use the charge timer to start at 2:10am every day and charge to 80%. I can override this at anytime by hitting the Charging Start button in the EV App and get it up to 100% whenever the range is needed. The car is always plugged in when not being driven, which allows remote Climate Control or Charging to be activated whenever desired.

 

[SageBrush]

Charging to 100% is not a problem. It is required, periodically, to keep the cells balanced. It is leaving it at 100% charge for extended periods of time, especially in high temperatures, that is the problem. For those without the ability to limit charging, use a timer so that charging completes just prior to the intended departure time.

I am one of the fortunate ones with a 2013 Leaf. I use the charge timer to start at 2:10am every day and charge to 80%. I can override this at anytime by hitting the Charging Start button in the EV App and get it up to 100% whenever the range is needed. The car is always plugged in when not being driven, which allows remote Climate Control or Charging to be activated whenever desired.

Agreed. Setting the charging end timer to about ~ one hour after the time the car is to be used may also work pretty well.

 

[goldbrick]

Thanks SageBrush (and cwerda) for exposing this. It's not really anything new although it does add a lot of credence to what used to be mostly anecdotal speculation.

FWIW, my strategy going forward is to charge the car every night just enough to get through the next day's driving. My use is almost entirely small trips and commuting. So far I've kept the car between 30% and 80% SOC as much as possible but sometimes I'm stuck in a meeting or forget to check it and it goes outside this range. I charge for free at work and usually charge about 2x or 3x a week.

I just bought an OpenEVSE since it appears to allow great scheduling or charging either by time or even amount of power. So.....once the weather gets hot this summer, I will charge X minutes or X kWh every night at 3AM or something to get through the next day. That should allow the battery to cool after my drive home and before my drive to work and will also charge when the inside of the garage is coolest. Plus it's a low usage time although I don't have to worry about TOS rates now.