Does lower effncy driving lead to more battery degradation?

[jlsoaz]

My dashboard display of efficiency reads 3.8 miles/kWh and every six months my dealer technician and I discuss a variety of things. He indicates that while my battery checkup is fine, the efficiency I am getting is at the low end of what he tends to see. He asks if I tend to drive in D mode and I say no. I indicated to him the low efficiency seems logical to me since I use the vehicle to drive around the county as I do my gasoline car, but that means a lot of trips of about 10 miles each way at 65-75 mph.

Setting aside the probably-inevitable criticisms from some but perhaps not all of the efficiency-focused folks, the reason I am mentioning all of this is that it got me to wondering whether there is a link between driving fast and hard over time, and battery degradation. Maybe it is hard to say what correlates to what.... I do live in a hot Arizona climate (though not as hot as Phoenix) and my battery has degraded a decent amount (about 187 gids showing at 80% charge).

Anyway, I don't recall if or to what extent, during the earlier degradation discussions, it was examined as to whether there might be a correlation between drivers who might average lower dashboard reported efficiency (whether due to climate or high speeds or what-have-you) and worse degradation over time.

I guess on a related note, I think the 8 bar/5-year solution to the battery warranty questions, as well as the battery replacement terms that were issued, were certainly better than not having clear answers, but were perhaps somewhat unrealistic in terms of really addressing the customer-satisfaction quandry faced by folks who have lost 2 or 3 bars and are trying to make good use of the car prior to lease end, or who are concerned with car valuation if they have purchased. Well, it's hopefully only a small percent of drivers who have to really concern themselves with these issues.

 

[LeftieBiker]

...the reason I am mentioning all of this is that it got me to wondering whether there is a link between driving fast and hard over time, and battery degradation.

That probably is related, but not efficiency in general.

 

[jlsoaz]

...the reason I am mentioning all of this is that it got me to wondering whether there is a link between driving fast and hard over time, and battery degradation.

That probably is related, but not efficiency in general.

I am getting more curious to see if it would be possible for us to look at the dashboard efficiency number, and I think dashboard average speed is available as well, in additional columns displayed at this Leaf Battery Survey page:
http://www.pluginamerica.org/surveys/batteries/leaf/vehicles.php" onclick="window.open(this.href);return false;

If I recall correctly, I think they may possibly collect one or both of these fields? I would encourage considering doing so, if they don't already.

fwiw, my vehicle is the one that is in Rio Rico, AZ.

 

[DNAinaGoodWay]

Well, if there is a correlation, would it be from fast driving adding to pack temp, especially in AZ. Plus maybe, more frequent QCs?

 

[Deleted member 14724]

I would think that the main difference in degradation would come from more charging cycles on the battery.

 

[TimLee]

...
I guess on a related note, I think the 8 bar/5-year solution to the battery warranty questions, as well as the battery replacement terms that were issued, were certainly better than not having clear answers, but were perhaps somewhat unrealistic in terms of really addressing the customer-satisfaction quandry faced by folks who have lost 2 or 3 bars and are trying to make good use of the car prior to lease end, or who are concerned with car valuation if they have purchased. Well, it's hopefully only a small percent of drivers who have to really concern themselves with these issues.

Short answer to OPs question is Yes.
More nuanced answer is Not a Large Amount.
Battery capacity does decline based on cycles and less efficient use is more cycles.
But for a large % of people time degradation and effects from battery temperature especially at a high status of charge are more significant.
You can run Stoaty's degradation model to quantify the difference for your situation.

I think 3.8 miles/kWh is a pretty good #.
Mine is more like 3.4 (and a lot more people have that and don't talk about it very much).
Depends on how you use the car.
Use a lot of heat or spend a lot of time in the car with it not moving or drive fast when you are late or all of the above and it can be pretty low.

On the last point, I think a fairly high % of LEAF purchasers will end up very disappointed in Nissan's capacity warranty. My guess is 95%.
A smaller % of leasors will end up disappointed.
Maybe 50% :?:

 

[Nubo]

I seem to recall hearing that for EV's higher drain rates actually correlate with better battery life. Not sure where I heard that; maybe transportevolved podcast…

edit: Found it…..

https://transportevolved.com/2014/09/30/comes-electric-car-battery-care-quick-discharging-might-help-battery-life/" onclick="window.open(this.href);return false;

 

[elmobob]

I've wondered the same thing, for example;

Leaf A: gently driven 50 miles a day with average efficiency of around 4 miles/kWh, discharged to 20% soc daily

Leaf B: driven with a lead foot with heater on blast and frequent 80 kW acceleration driven in highway 25 miles a day with an average efficiency of around 2 - 3 miles/kWh, discharged to 20% soc daily

provided climate and average battery temperature is the same because both cars live in the same region, which battery would degrade faster after say 3 years?

I guess Nissan with all their data collection is the only one that could answer this accurately.

btw I fit the description of driver B in the winter time here in NY, in summer I sometimes see 3.6 miles /kWh but in winter I see 2-3 miles a kWh depending on how cold it is. After having the car for 33 months and 26,883 miles according to leafspy Hx=71.20%, SOH=85% the car still shows 12 bars.

 

[Stoaty]

I seem to recall hearing that for EV's higher drain rates actually correlate with better battery life. Not sure where I heard that; maybe transportevolved podcast…

edit: Found it…..

https://transportevolved.com/2014/09/30/comes-electric-car-battery-care-quick-discharging-might-help-battery-life/" onclick="window.open(this.href);return false;

Only problem with this theory is that QC in Arizona was shown to moderately shorten battery life compared to L2 charging (NREL study). In the article above, rapid charging did not shorten battery life. So, may not be applicable to Nissan Leaf battery. In addition, my Leaf has been driven very gently and has tracked the Battery Aging Model quite closely. I suspect that the increased cycling necessitated by more rapid discharge may be a bigger factor in battery capacity loss than any potential benefit from rapid discharge.

 

[jlsoaz]

Well, if there is a correlation, would it be from fast driving adding to pack temp, especially in AZ. Plus maybe, more frequent QCs?

I've read through the various responses, and while they are ahead of my thinking, my one abiding thought is I'm not sure if all the answers are known with certainty... there would seem to be a few complicating points.

To your point, as to driving fast in AZ, isn't there a counter-point that while it may heat up the battery to exert a lot of power over more than a few seconds, perhaps as well it cools down the battery a bit better to have the air rushing into the car at about 75 mph? It would I guess depend on the temperature of the air as to whether it substantially works to help the battery cool. It's not always hot every day or all year round where I live. Sometimes it is below freezing.

I did go to this link which I found at the bottom of Stoaty's post:

http://www.electricvehiclewiki.com/?title=Battery_Capacity_Loss#Battery_Aging_Model" onclick="window.open(this.href);return false;

...If you spend a large part of the summer with seven temperature bars or more showing... It's probably best to avoid the Leaf completely. Consider an EV with an active thermal management system or the Chevy Volt....

That would certainly describe my experience. In the winter, I do generally see about 5 bars, but in the summer, it's a pretty steady 7 bars (maybe even a bit more, such as if I have to stop at a public charge station that is in direct sunlight).

I guess I came to these questions in part because I am losing capacity somewhat quickly, probably in line with the predictions.

Several people mentioned quick charging. Since my battery degraded and I can no longer make Tucson in one slow shot I have no real access to quick charge stations, so I doubt it's much of a factor in my particular case.

I do think though that charging outside without shade (heck they have shade at a lot of gas pumps, why not at EV charge stations?) has been a factor, along with sometimes parking in the sun and basically baking the car a bit. These types of scenarios I think would correlate somewhat with the higher temperature bar readings. (Note, I do generally try to make prudent decisions to not harm the battery needlessly, such as where possible avoiding charging in the Arizona sun.).

 

[Moof]

I seem to recall hearing that for EV's higher drain rates actually correlate with better battery life. Not sure where I heard that; maybe transportevolved podcast…

edit: Found it…..

https://transportevolved.com/2014/09/30/comes-electric-car-battery-care-quick-discharging-might-help-battery-life/" onclick="window.open(this.href);return false;

Only problem with this theory is that QC in Arizona was shown to moderately shorten battery life compared to L2 charging (NREL study). In the article above, rapid charging did not shorten battery life. So, may not be applicable to Nissan Leaf battery. In addition, my Leaf has been driven very gently and has tracked the Battery Aging Model quite closely. I suspect that the increased cycling necessitated by more rapid discharge may be a bigger factor in battery capacity loss than any potential benefit from rapid discharge.

It was roughly 27% vs. 24% degradation between doing only 2 daily quick charges on a couple cars and 2 daily level 2 charges on another couple identical cars, so for a person doing even half their charging on a QC you are only looking at ~1-2% extra degradation over level 2 only. Nissan's original warnings on QC's appear to be vastly overstated.

Back to the OP...
The battery takes a hit from just existing (calender loss) that is strongly influenced by heat. It is also subject to cycling loss. Lower efficiency would result in you cycling energy into and out of the pack more often than others. Cycling degradation is something like 2%/10,000 miles for cycling loss, so if you are 10% less efficient in your driving you might degrade your battery another ~0.2%/10,000 miles, or an extra 2% over the first 100k miles. It will likely pale in comparison to the calender loss in Arizona, so likely not worth worrying about.

 

[dgpcolorado]

I see significantly increased battery heating when using high discharge power levels. I also see reduced battery capacity in the days after flooring the accelerator for a time; I think I recall seeing that rapid discharge is bad for Li-ion battery chemistry, but can't recall where.

My hypothesis is that one of the factors that is causing my moderate capacity loss despite a rather cool climate is because I drive steep hills most of the time and the power levels needed to do that, even at moderate speeds, cause the battery to reach temperatures much higher than ambient.

So, additional cycling aside, my guess is that inefficient driving involving high acceleration power levels will lead to increased battery degradation due to increased heat and, perhaps, chemistry damage to the battery from higher discharge rates.