Battery Lifetime

[Anonymous]

Hi all, I think this is the right location for this post, but if it's not, feel free to move it.

I was wondering what the lifetime of the batteries would be on the Chevy Bolt. I know this is a bit premature since they haven't sold any yet and aren't available, so we don't have any real life data on it, but I thought we would at least start the conversation with known EVs and the battery type being used in the Bolt.

Thanks!

 

[WetEV]

I was wondering what the lifetime of the batteries would be on the Chevy Bolt.

Best indication to non-insiders is likely the battery capacity warranty. You can count on the majority of failures being at least a few months and a few miles over the capacity warranty.

Should be at least a factor of 2 or 3 variation in battery life across the USA. People in hot, steep places that drive fast and DCQC more will see faster capacity loss. If you live in a cool place with few hills, drive slow and never DCQC your battery will live on and on.

 

[SparkE]

I was wondering what the lifetime of the batteries would be on the Chevy Bolt.

Best indication to non-insiders is likely the battery capacity warranty. You can count on the majority of failures being at least a few months and a few miles over the capacity warranty.

Should be at least a factor of 2 or 3 variation in battery life across the USA. People in hot, steep places that drive fast and DCQC more will see faster capacity loss. If you live in a cool place with few hills, drive slow and never DCQC your battery will live on and on.

AND try and generally keep your batteries State Of Chage (SoC, i.e., "battery fullness") between 20% and 80%.

Also, the Bolt has an active thermal temp management system, like the Spark and Volt do (it pumps cooling or heating liquid around the battery to keep it at a 'friendly' temperature). The LEAF has a passive, air-cooled battery. There have been very few reports of battery fade on the Chevys that have been shipping for years - on the other hand, LEAFs are notorious for having battery fade after 3-4 years (loss of 25-35% of capacity).

I would hope that GM would have at least as good a system in the Bolt as in the SparkEV or Volt.

 

[splitmitten]

Hyundai says it's batteries are meant to last the lifetime of the vehicle. Is this possible?

 

[SparkE]

Hyundai says it's batteries are meant to last the lifetime of the vehicle. Is this possible?

Yes.

 

[Anonymous]

Its definitely a good sign in the Volt doesn't have much battery life degradation. I guess this may have been their test bed for battery life management before they went full out EV on cars like the Bolt. Time will tell.

Regarding Hyundais claim, that's very surprising, although "Life of the vehicle" is too vague of a term to bank anything on, sounds like someone in their marketing department needs to learn about quantitative measures. Unfortunately, a lot of car manufacturers use ~4 years as the life of the vehicle since most people swap out cars after the lease cycle these days.

 

[GetOffYourGas]

Regarding Hyundais claim, that's very surprising, although "Life of the vehicle" is too vague of a term to bank anything on, sounds like someone in their marketing department needs to learn about quantitative measures. Unfortunately, a lot of car manufacturers use ~4 years as the life of the vehicle since most people swap out cars after the lease cycle these days.

The trouble with using 4 years is that those lease turn-ins are resold and therefore hardly at the end of their life.

In my experience, the life of a vehicle is about 15 years / 200k miles. Hyundai's battery will probably still propel the car at that point, but you can bet that it won't function in like-new condition. On the other hand, the Volt's battery just might still seem as good as new at that point. Time will tell.

 

[michael]

The Volt's battery is likely to last much better than most, because only a small portion of the charge window is used and there is an aggressive temperature management system. In addition, since only a small portion is used, they may gradually increase the window to mask battery fade.

Mine still delivers 10.4 kWh useful after 36,000 miles, but that may or may not mask underlying fade.

That said, no battery lasts forever. They all fade a little bit every time they are used. The amount of fade depends on battery construction and chemistry, on charge/discharge profiles, on temperature, and on who knows what else.

The lithium-cobalt batteries used in the Honda FIT EV exhibit extremely long lifetime, but fall on their faces in cold weather. Everything is a compromise.

Regarding "life the the vehicle" claims...when the battery is dead, so is the car. That was the life of the vehicle. Just empty marketing talk.


"When new, the battery in our car will propel the car 100 miles if driven in a manner to use 250 Wh/mile. It is guaranteed to provide at least 80% of that range for 7 years/80,000 miles, whichever comes first"

The above is an example of a real guarantee. Ever see a car maker say something like that?

 

[devbolt]

Lifetime of the car means the actual lifetime of the car, from the first mile where it's produced at the factory until the last mile where it ends up in the junk yard. Not from when the owner gets tired of it and trades it in on a new model. The average age of cars on the road in the US is 11.5 years old. It's not unreasonable to expect the Bolt to last a minimum of 10 years barring a catastrophic crash or failure of the car.

The death of the battery in an EV may not be a death knell for the car itself. Assuming that the rest of the car is in good working condition, it may well be worth it to replace the dead battery with a new one, or a lightly used one from a donor crashed car, for a fraction of the cost of a new EV. This is what played out in the hybrid world where people were predicting that Prius hybrid batteries would have to replaced after 5 years for over $5K. Turned out they last way longer than that and used replacement battery packs could be had for under a grand. Rebuilt ones were available for two grand or thereabouts. If you buy a brand-new battery pack for a 2nd generation Prius from Toyota, it's around $3200 including installation.

 

[Michael1]

Good article here on battery life. It includes both time, temperature, and cycle factors. Degradation starts the day the battery is built.

http://www.electricvehiclewiki.com/Battery_Capacity_Loss

 

[michael]

One huge advantage of the Bolt over all current 80 mile class cars is that very very few people will need to use any appreciable amount of its capacity most of the time. The battery can be kept within a "happy" window and will degrade far, far slower than heavily utilized batteries.

Plus...when it's down 25%, it's still a 180 mile car. My Focus, when down 22% at least end, was crippled, marginal for what I needed it to do. The Bolt would be loafing.

 

[Zoomit]

Battery degradation is complicated of course, but average charge state and discharge cycles both play into it. It's different for the battery to be cycled between 80-100% SoC vs 50-70%, especially in hot climates. Here the average charge is ~90% vs ~60% and the battery will prefer the lower average state.

But both those scenarios only use a fraction of the total charge. An 80-mi range car might need to use nearly a full discharge cycle each day, while a 240-mi car may use only a quarter. So every four days, it does one equivalent discharge cycle, verses every day for the shorter range car. In one year, the long range-car might do 65 discharge cycles, where the short-range car does 260 cycles.

For more: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

 

[Anonymous]

I think the Bolt battery should fare very well considering its LG Chem sourced and not a new tech. Based from a concern about battery longevity I wrote an Android and iOS App called EvBatMon which currently supports iMiEV and OutlanderPHEV and partially supports Chevy Spark EV and Kia Soul EV. It allows owners to compare their real world battery degradation to other owners via the App and upload it to a cloud portal to produce graphs like this -
http://www.evpositive.com/battery-history.html
If anyone has the expertise to determine the CANbus codes for the Bolt battery (or knows they are similar to the SparkEV?), I would love to add support for the Chevy Bolt to the EvBatMon App.

 

[Zoomit]

Looks like a good app. I'm waiting patiently for the Spark EV iOS version. I'd think Bolt EV bus traffic might be similar.

 

[Anonymous]

Looks like a good app. I'm waiting patiently for the Spark EV iOS version. I'd think Bolt EV bus traffic might be similar.

I could release the Spark EV iOS version next week however I was unable to read some key data (odometer ?) which has stalled progress in supporting the Spark EV. Unfortunately without access to the Spark EV or Bolt here in Australia I have to rely on CANbus "hackers" over in the States to determine the PID for EvBatMon to use. PM me if you're interested in helping out.

 

[michael]

Battery degradation is complicated of course, but average charge state and discharge cycles both play into it. It's different for the battery to be cycled between 80-100% SoC vs 50-70%, especially in hot climates. Here the average charge is ~90% vs ~60% and the battery will prefer the lower average state.

But both those scenarios only use a fraction of the total charge. An 80-mi range car might need to use nearly a full discharge cycle each day, while a 240-mi car may use only a quarter. So every four days, it does one equivalent discharge cycle, verses every day for the shorter range car. In one year, the long range-car might do 65 discharge cycles, where the short-range car does 260 cycles.

For more: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

I'm not sure exactly which option you are recommending, but here is my vies. If, for example, typical daily use required 25% of the battery capacity, there are five options which one might choose (obviously there are others, this just to illustrate the point):

1. Fully charge it every four days, recharge when empty
2. Run it every day between 100 and 75%
3. Run it every day between 75 and 50%
4. Run it every day between 50 and 25%
5. Run it every day between 25 and 0 %

Even though the first option provides the fewest charging cycles, it is not the easiest on the battery, and should be avoided.

It is generally agreed that option 2 is not desirable because it causes the battery to spend some time at full charge. However many people will do this anyhow because it's the easiest (let the battery charge til it stops) and because it provides the most reserve enery.

There is differing opinion between 3, 4, and 5. Most people would prefer 3 or 4, although at least one scientific papers states that 5 is best. 5, however is least flexible since there is no reserve. Most people would probably select 3 since it provides plenty of reserve energy without ever fully charging or discharging the battery.

 

[Zoomit]

1. Fully charge it every four days, recharge when empty
2. Run it every day between 100 and 75%
3. Run it every day between 75 and 50%
4. Run it every day between 50 and 25%
5. Run it every day between 25 and 0 %

Even though the first option provides the fewest charging cycles, it is not the easiest on the battery, and should be avoided.

It is generally agreed that option 2 is not desirable because it causes the battery to spend some time at full charge. However many people will do this anyhow because it's the easiest (let the battery charge til it stops) and because it provides the most reserve enery.

There is differing opinion between 3, 4, and 5. Most people would prefer 3 or 4, although at least one scientific papers states that 5 is best. 5, however is least flexible since there is no reserve. Most people would probably select 3 since it provides plenty of reserve energy without ever fully charging or discharging the battery.

I think 3 or 4 is technically best for the battery, but you've characterized it well. Having reserve is important and to me it is not worth fretting over possible battery life degradation. With our Spark EV, we use it ~20 miles daily around town and charge it when it gets below 33% or 25% full (case 1). This is definitely more convenient than plugging it in and unplugging it daily.

If you're anxious about your battery, I'd feel very confident just setting the Bolt EV to Hill Top Reserve (90% max recharge) and forgetting about it. But I also wouldn't be concerned about charging it to 100%, unless I was leaving it at that level at high temperatures frequently. For example, an Arizona owner with a short commute. The battery would be sitting in the sun most days with >90% charge state. For virtually everyone else, just use it.

 

[JeffN]

For example, an Arizona owner with a short commute. The battery would be sitting in the sun most days with >90% charge state. For virtually everyone else, just use it.

Agreed that Arizona owners should be somewhat concerned about leaving a car sitting at high SOC. However, I was told by a GM media rep passing along information from the engineering folks that the Bolt EV will automatically cool the battery pack to protect it when the pack is at a high SOC and temperatures are high -- even if the car is not plugged in.

Unfortunate, GM would not say what the specific SOC and temperature conditions are that trigger battery pack cooling like this when unplugged. Presumably, it prevents the worst degradation conditions but it may still be better off overall to have the pack at 50% SOC when sitting in an Arizona parking lot all day at work than to have it charged to "100%" and have the automatic battery cooling kick in. We really need more information about how it works to understand the tradeoffs. Arizona owners should be able to observe when their cars self-protect in the heat and reverse engineer what the parameters and algorithm is.

 

[JeffN]

For example, an Arizona owner with a short commute. The battery would be sitting in the sun most days with >90% charge state. For virtually everyone else, just use it.

Agreed that Arizona owners should be somewhat concerned about leaving a car sitting at high SOC. However, I was told by a GM media rep passing along information from the engineering folks that the Bolt EV will automatically cool the battery pack to protect it when the pack is at a high SOC and temperatures are high -- even if the car is not plugged in.

Unfortunate, GM would not say what the specific SOC and temperature conditions are that trigger battery pack cooling like this when unplugged. Presumably, it prevents the worst degradation conditions but it may still be better off overall to have the pack at 50% SOC when sitting in an Arizona parking lot all day at work than to have it charged to "100%" and have the automatic battery cooling kick in. We really need more information about how it works to understand the tradeoffs. Arizona owners should be able to observe when their cars self-protect in the heat and reverse engineer what the parameters and algorithm is.

Of course, park in the shade or in a covered garage whenever possible in Phoenix on hot days....

 

[Zoomit]

I remember hot conditions living in Las Vegas that would be horrendous for an EV. Our cars would get heat-soaked sitting outside during the day then we'd put them both in the garage at night. I'd open the garage the next morning and the temperature would still be over 100F in there. The car's components cycled between 110-140F during the day to a min of only 100F at night. This was a typical summer day.

I'd wish that on no car, especially an EV.