Does fast acceleration cause battery degradation?

[MarkBC]

I was thinking that the amount of electricity liberated by fast acceleration is well into the range accepted by the battery during a fast charge, which is not recommended as a regular charge option so as to maintain battery life. But fast acceleration happens many times per day. Is this something I should try to avoid?

 

[mkjayakumar]

I think this was discussed elsewhere in this forum. The logic goes something like, during acceleration and also during regen, discharge and charges happen at around the same rate as QCDC, but then it happens in spurts which lasts no more than a few seconds. This opposed to a fast charging through a QCDC that happens over 30 to 60 minutes.

So when you step on the gas and go from 0 to 60 in 10 seconds and then step on the breaks and stop in 6 seconds the charge / discharging at high rates is for less than 10 seconds. Not so bad for the battery..

 

[Anonymous]

Mark,
Hard acceleration can be deleterious to any lithium pack, including the LEAF. The culprit is heat.
When you accelerate hard, huge currents flow through your pack and, depending upon the cell chemistry, and its internal resistance, heat is generated from this current flow. This heat can degrade the cell contents over time.
I'm very conservative in our LEAF, as we want to get maximum lifetime out of our battery pack. I have only really 'floored it' a couple times, just to know what it's capable of.
The LEAF has taught us to drive much more slowly than before, for the most part.
Lithium cells inherently lose roughly 1.5-2% capacity per year, and I want to minimize any further losses.

 

[surfingslovak]

Lithium cells inherently lose roughly 1.5-2% capacity per year, and I want to minimize any further losses.

Agree with what you said about acceleration. I thought the same thing about the anticipated battery capacity loss, until I measured about 10% loss in my Leaf after the first year, and saw the graph below (thank you, TickTock). Additionally, while it's fairly easy to agree on good battery care practices and conservative driving, sadly, we have not seen much benefit from that in places like Phoenix, where all packs seem to go bye-bye after 1 1/2 or 2 years. It difficult to quantify the effect of proper battery care given the available data.

 

[smkettner]

I suggest everything in moderation. Full throttle when actually needed will not hurt because it is rarely if ever needed.
Frequent fast starts just for fun will have an effect on battery life, JMHO.

 

[EVDRIVER]

I
Frequent fast starts just for fun will have an effect on battery life, JMHO.

Based on what? Heat? I floor my LEAF very often, my pack temp never goes over 70-72 95% of the time. Only once did my pack b=go above 75 and that was close to 100 in a warmer climate.

 

[smkettner]

General life experience. Ever meet people that contantly have stuff that breaks and meet others where they can make stuff last forever?
It always amazes me when the person with broken stuff rarely thinks his actions had anything to do with the outcome.

Anyway I did not quantify the amount. I did express it was just an opinion.

 

[EVDRIVER]

General life experience. Ever meet people that contantly have stuff that breaks and meet others where they can make stuff last forever?
It always amazes me when the person with broken stuff rarely thinks his actions had anything to do with the outcome.

Anyway I did not quantify the amount. I did express it was just an opinion.

I asked about the actual reason not the amount, why exactly do you think hard accel will degrade the pack, even with low pack temps?

 

[ericsf]

In fact this is where the LEAF's pack should perform better than other Lithium Ion battery chemistries. Due to its very low internal resistance the Li-Mn can take discarge power higher than Li-Co without occuring dangerous heat buildup. Yep, we're back to discussing heat.

Source : http://batteryuniversity.com/learn/article/types_of_lithium_ion

 

[smkettner]

Still you are using more energy per mile. Driven hard for 75,000 miles and driven nicely for 75,000 miles do you honestly think the batteries will average out the same? (all other things being equal)

 

[EVDRIVER]

Still you are using more energy per mile. Driven hard for 75,000 miles and driven nicely for 75,000 miles do you honestly think the batteries will average out the same? (all other things being equal)

Not according to some that seem to think flooring the car is more efficient, which I find entertaining. Regardless, miles per kwh is not the same as degrading it is efficiency over the life of the pack. My question to you is how does the pack degrade faster from flooring it when heat is NOT an issue?

 

[bowthom]

Still you are using more energy per mile. Driven hard for 75,000 miles and driven nicely for 75,000 miles do you honestly think the batteries will average out the same? (all other things being equal)

Not according to some that seem to think flooring the car is more efficient, which I find entertaining. Regardless, miles per kwh is not the same as degrading it is efficiency over the life of the pack. My question to you is how does the pack degrade faster from flooring it when heat is NOT an issue?

General answer: Heat is always an issue. The overall pack temp may not go up appreciably but down at the molecular level high current = high temp rise which breaks down the electrolyte. Think candle in a room, there is a hot spot but the overall temp of the room will not rise that much.

I hope that analogy helps explain it some............

 

[Nubo]

full-throttle acceleration uses 90kW. Given a 24kWH pack, that is is less than a 4C discharge, and you can only maintain that level for a matter of seconds before you either reach your cruising speed or 94 mph, whichever comes first. For driving on public roads, acceleration is not too big a factor in overall life of the battery, I'd reckon.

 

[smkettner]

Not according to some that seem to think flooring the car is more efficient, which I find entertaining.

Yes, I was told once that by driving faster and getting home faster less fuel is used :lol:
That was a driver of a big SUV :roll:

 

[thankyouOB]

i think acceleration would have an effect.

i have seen the heat phenomenon with sustained speed over time, too.
on days when pack is running a five-bar battery temp, i have frequently seen it crest and stay in six bars after driving at freeway speeds for 6-9 miles.

 

[ztanos]

I
Frequent fast starts just for fun will have an effect on battery life, JMHO.

Based on what? Heat? I floor my LEAF very often, my pack temp never goes over 70-72 95% of the time. Only once did my pack b=go above 75 and that was close to 100 in a warmer climate.

How do you know that you don't go above 75? Is that the mark for 6 bars?

 

[ztanos]

Still you are using more energy per mile. Driven hard for 75,000 miles and driven nicely for 75,000 miles do you honestly think the batteries will average out the same? (all other things being equal)

Not according to some that seem to think flooring the car is more efficient, which I find entertaining. Regardless, miles per kwh is not the same as degrading it is efficiency over the life of the pack. My question to you is how does the pack degrade faster from flooring it when heat is NOT an issue?

Wouldn't accelerating quicker use more of a charge out of the battery? Causing you to recharge the battery more often, thus you would blow through quicker cycles and hit EOL quicker. This is the same reasoning that people use to claim that regen braking is bad for the car.

 

[EVDRIVER]

I
Frequent fast starts just for fun will have an effect on battery life, JMHO.

Based on what? Heat? I floor my LEAF very often, my pack temp never goes over 70-72 95% of the time. Only once did my pack b=go above 75 and that was close to 100 in a warmer climate.

How do you know that you don't go above 75? Is that the mark for 6 bars?

I have monitored my pack temp via consult repeatedly. It is so cold in my garage most of the year my pack stays below 65 even with some freeway driving. Once in Napa I hit 100 after charging while it was hot.

 

[TickTock]

According to Nissan, at 90mph you lose 5% of the available charge in your battery to heat losses. This alone means you will have to charge/discharge 5% more over life which does contribute to degradation. However, this is dwarfed by the extra wind drag on the car at that speed. On flat ground, 90mph requires 40kw to sustain. 55mph requires 12kW to sustain. So at 55mph you use 19.6kW to travel 90 miles. Call it 20. --> 90mph doubles number of charge/discharge cycles required to drive the same distance. That seems pretty significant to me.

 

[planet4ever]

Wouldn't accelerating quicker use more of a charge out of the battery?

I don't know. Why would it? If you accelerate to the same speed then, whether you do it fast or slow, you are adding the same amount of kinetic energy to the car. If the battery and motor and drive train were 100% efficient, and you were driving in a vacuum, the amount of energy used would be the same, no matter what the acceleration. Of course none of those things are true, so we have to look at where the losses are. Motor efficiency does drop off very slightly with increased torque, but not enough to notice. (It's actually worst at very low torque.) I would think the same is true with the drive train. That leaves the battery (taking us back to heat) and air resistance. The faster you accelerate the more time you spend at your target speed, so if that speed is high enough that air resistance matters, then the difference might be significant. But only if you weren't going to retain that speed very long.

So, once again, why would accelerating quicker use more of a charge out of the battery? The only significant answer I am seeing is battery heat.

Ray