Battery Health and longevity

[Jfcrabbit]

Have any reports or research been done on the difference of health and cost of charging the batteries when routinely charged with Level 1,2 or 3 charging. When there is a choice and no time issue evolved what is the difference of cost and affect on the batteries. Owners manual is a little light on this subject.
Thanks

 

[rgmichel]

I suppose it might have an effect beyond the warranty of eight years or 100k miles? The conventional wisdom is that DC fast charging is not as good for the battery as level 2 charging, and that level 1 charging is too slow.

 

[Domenick]

Degradation from fast charging varies by chemistry, with some of the less energy dense cells able to deal with it much better than more energy dense cells. And even then, fast charging only causes degradation as the battery becomes full.

You can think of it like cars in a parking lot. When a parking lot is empty, cars can flow in and park at a pretty fast rate. As the lot fills up, it takes cars longer to find a spot and park. If they're being pressured to park by a long line of cars behind them, there will likely be mistakes made and damage will occur.

The cars are lithium ions and the parking lot is the anode. This is why charge speed, even with DC fast charging,slows down as it gets closer to full. Really, there shouldn't be appreciable damage if the charging speed is well matched to the battery chemistry. It hasn't been perfect in the past, but no doubt there are improvements.

 

[Pushmi-Pullyu]

To be safe, avoid DCFC ("Level 3") as much as possible. I've also seen claims that L1 charging is worse for long-term battery life than L2 charging, supposedly because L1 is less efficient and therefore heats up the battery more than L2 charging... but I'm rather skeptical of such claims. I haven't seen any hard data to back that up.

There are other issues you should be aware of. For example, repeatedly charging to 100% or discharging to the point that the car "turns turtle" or comes close to 0% charge, is bad for battery life. In general, you should charge the car every day or night and try to balance your daily driving around a 50% charge. For example, if you typically use 40% of the battery pack during a daily drive, you should charge to 70% and discharge to 30%, rather than say charging to 80% and discharging to 40%. Or, if you typically use 50% of the battery's full capacity in a day's driving, then charge to 75% and discharge to 25%.

Of course, if you're going on a long trip, or you'd like to have the option of a second trip the same day that will challenge the car's EV range, then you should charge to 100% and not worry about battery life. Charging to 100% only occasionally shouldn't have any noticeable impact on battery life.

 

[Aircooled6]

P. 231 of the Bolt owner's manual: "It is recommended that the vehicle be plugged in when temperatures are below 0 degrees C (32 degrees F) and above 32 degrees C (90 degrees F) to maximize high voltage battery life." Now, it is 21 degrees outside and the battery has maxed to 100 % charge. Take it off charge or leave it on? Also, this is Dallas, it begins to get above 90 degrees around mid April and lasts until November. What do I do if I have to park (very often) where there is no access to a plug? The same applies to when the temperature is below 0 C. What kind of battery degradation (longevity or capacity) would I expect to have? I just called Chevrolet and they acted like it is the first time they ever heard the question (call line operator). They asked that I call my dealer. Not a great idea as they were not even sure that the car I was looking at had the Level 3 charge connection of not. I had to point it out to them.

 

[Pushmi-Pullyu]

P. 231 of the Bolt owner's manual: "It is recommended that the vehicle be plugged in when temperatures are below 0 degrees C (32 degrees F) and above 32 degrees C (90 degrees F) to maximize high voltage battery life." Now, it is 21 degrees outside and the battery has maxed to 100 % charge. Take it off charge or leave it on?

I'm not a Bolt EV driver, but based on extensive reading about the subject of plug-in EVs in general, and specifically BEVs with a large battery pack like the Bolt EV:

Leave it on the charger if the outside temperature is below 32° F or above 90°, or you expect the temperature to get that high or low before using the car again. I wouldn't worry about overcharging the battery by leaving it plugged in. That's why the car has a BMS; to prevent that from happening.

But you shouldn't be charging to 100% on a daily basis; that's very bad for battery life in a BEV like the Bolt EV. (It's probably okay in the Volt, and perhaps in some other PHEVs which have a large reserve capacity which usually isn't used.) Sure, charge to 100% when you're going to be challenging the car's range the next day, but hopefully you will be doing that only rarely.

Also, this is Dallas, it begins to get above 90 degrees around mid April and lasts until November. What do I do if I have to park (very often) where there is no access to a plug?

Well, first of all: I believe you're talking about a daily high of 90° F, not -- as happens in Phoenix -- an average daily temperature of 90° or higher. It is sustained high temperatures, and high temperatures in wet climates (i.e., Florida and New Orleans), which cause premature battery aging. But that aside: When it's very hot outside, park in the shade whenever you can. (That's good advice even for a gasmobile; letting the inside of your car act like a solar oven isn't good for the seats or other interior trim!) Otherwise, don't worry about the heat. Your car has a liquid cooling system for the battery pack, so you shouldn't experience the kind of premature battery aging that all too many Leaf owners experience in hot climates.

The same applies to when the temperature is below 0 C. What kind of battery degradation (longevity or capacity) would I expect to have?

We need to make a clear differentiation between what you do on a daily basis, and what you do only occasionally. On an everyday basis, you should not leave your car parked outside overnight without being plugged in, when the temperature will drop below freezing. If you need to do this occasionally, such as when you're on vacation, then don't worry about it; but if it gets bitterly cold, let's say below 20° F, then you are advised to figure out some way to plug it in, even if it's just plugged into an ordinary wall outlet using daisy-chained extension cords. (But you should invest in some properly rated extension cords and carry those in your car. Using an off-the-shelf extension cord, even heavy-duty ones, can be a fire hazard.)

The problem with leaving the car out when it's bitterly cold is not so much with premature aging. The problem is that the battery pack has significantly lower capacity when it's very cold, and in fact most EVs are engineered not to charge when the battery pack gets too cold. I question that leaving the car outside when it's really cold will make any noticeable contribution to premature battery aging. Maybe it will, but I haven't seen any warnings about that, so that wouldn't be my concern. The concern is that you're going to be surprised and disappointed at the significantly reduced range from a very cold battery. But if you leave the car plugged in, then it should run the battery heater as necessary to keep the pack above freezing temperature.

One thing you should be aware of is that batteries have greater capacity when they're warm than when they're cold. If you charge to 100% while the pack is overheated... then that might well cause premature battery aging. I'd avoid that as much as possible. Otherwise, as I said, you shouldn't worry too much about the battery pack getting too hot in hot weather. Only EVs with no liquid cooling system have a problem with that causing premature battery aging, and again the Bolt EV has a liquid cooling system for the pack, so you're good.

Caveat: There are some assumptions in what I've said here. I know that GM has done an excellent job with engineering the Volt's (PHEV) battery pack; such a great job that very few incidents of problems with its battery have been reported. I'm assuming that GM has done, at least, not much worse with the Bolt EV, but the build is actually by LG Electronics' brand-new automotive division. I think for common sense purposes it's reasonably safe to assume that GM has watched over LG Electronics' production, and has done their own extensive testing; so it seems reasonably safe to assume that the Bolt EV's powertrain will be another product of GM's mostly very good or excellent engineering. But that still is an assumption... and you know what they say about assumptions.

On the positive side, Tesla has proven that with larger battery packs protected by liquid cooling, battery longevity simply isn't an issue in the vast majority of cases. Since the Bolt EV also has a large battery pack, I am assuming the packs will age quite slowly, just like they do on Tesla cars. Again, though... that's an assumption. We need to watch reports from actual Bolt EV owners to see what they experience in real-world conditions. Unfortunately, it's going to take a few years before we get enough real-world data to see what the trend is with battery aging in the Bolt EV, just as happened with the Model S.
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[Cypress]

To be safe, avoid DCFC ("Level 3") as much as possible. I've also seen claims that L1 charging is worse for long-term battery life than L2 charging, supposedly because L1 is less efficient and therefore heats up the battery more than L2 charging... but I'm rather skeptical of such claims. I haven't seen any hard data to back that up.

There are other issues you should be aware of. For example, repeatedly charging to 100% or discharging to the point that the car "turns turtle" or comes close to 0% charge, is bad for battery life. In general, you should charge the car every day or night and try to balance your daily driving around a 50% charge. For example, if you typically use 40% of the battery pack during a daily drive, you should charge to 70% and discharge to 30%, rather than say charging to 80% and discharging to 40%. Or, if you typically use 50% of the battery's full capacity in a day's driving, then charge to 75% and discharge to 25%.

Of course, if you're going on a long trip, or you'd like to have the option of a second trip the same day that will challenge the car's EV range, then you should charge to 100% and not worry about battery life. Charging to 100% only occasionally shouldn't have any noticeable impact on battery life.

Note that for lower range EVs, this may not be practical. My Spark EV is rated for just 86miles. So trying to play 80%-30% games to extend the battery life a little longer is too much hassle and would make the car mostly useless. Also, the battery capacity itself is something like 21kWh but they limit it to 19kwh. So it already has some buffer. When it says it has charged to 100%, that’s 100% of 19, or the actual pack capacity. I expect the Bolt battery also has some built in buffer to it, but I’m not sure.

Just use your vehicle. It’s covered by warranty.

 

[WalksOnDirt]

Just use your vehicle. It’s covered by warranty.

This is where the 80% charging that the EPA discourages is so useful. If 80% covers your typical day, use it. Otherwise, don't.

 

[Pushmi-Pullyu]

Note that for lower range EVs, this may not be practical. My Spark EV is rated for just 86miles. So trying to play 80%-30% games to extend the battery life a little longer is too much hassle and would make the car mostly useless.

Obviously trying to push the limit of any BEV on a daily basis is problematic. That's something a would-be buyer should consider before buying a BEV. Consideration after... well, it's a bit too late.

My advice for would-be BEV buyers in temperate climates (i.e., where one can expect some very cold days in winter) is to make sure the car's EPA-estimated range is at least 40% greater than the anticipated daily driving range; that allows for both lower range with extended highway driving, and also range reduction on cold days. Buyers in more Mediterranean climates (i.e., southern California) can likely get by with 20-25% over daily range.

Also, the battery capacity itself is something like 21kWh but they limit it to 19kwh. So it already has some buffer. When it says it has charged to 100%, that’s 100% of 19, or the actual pack capacity.

Hmm, I guess we're going to have confusion over word usage here, because I would call 21 kWh the "actual" capacity, and 19 kWh the "usable" capacity.

I expect the Bolt battery also has some built in buffer to it, but I’m not sure.

My guess is that the Bolt EV, like Tesla cars, has somewhere around a 4-8% buffer. But that's only a guess.

 

[Butch777]

At the risk of taking this thread in a new direction, are there any considerations for Bolt owners on 220v charging vs. good old 110v wall outlet, which comes standard with the car? The reason I ask is that i've leased my Bolt for almost a year and have concluded that I don't need a fast(er) charging solution @home, as I don't take it on long trips and there is a fast charger where I work. Has anyone done the math on the cost of electricity @ 110v vs. 220v or is it all the same?

And, per the previous discussion, I'm not going to lose sleep over 50% vs. 80% vs. 100% charging, as I turn the car back to the dealer in 2 years. Let me know if I'm off base here.

 

[Pushmi-Pullyu]

Has anyone done the math on the cost of electricity @ 110v vs. 220v or is it all the same?

I've read that L2 charging (220v) is slightly more energy efficient for some cars, altho I don't know if that applies to the Bolt EV or not.

What I can say is that it's very unlikely that a few cents' difference in cost per charge, over the space of just a year, is going to pay for the cost of having an electrician install a dedicated 220v circuit in your garage, or wherever you have your charger.

Of course, looking forward, if you plan to replace the Bolt EV with another plug-in EV, then in the long run it will be more cost-effective to install a L2 charger now than to do it at a later date. But do call around and get a few different bids, if you decide to go ahead and do that. Some electricians charge far more than they ought to for that sort of thing.

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[ekutter]

I have a 220v (12amp) charger for my Volvo that I plan on using with the Bolt which should be more than enough for me. Considered putting in a 2nd faster L2 charger but the cost will never pay for itself on just the Bolt. Even an L1 charger would probably be sufficient with the amount we drive.

I also figure it's better to push off any upgrades as long as possible as we don't know what will be standard 2+ years out. Good chance my next BEV will be a Model Y. But that decision is a ways off.