Is battery life dependent on ambient charging temperature?

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RegGuheert

Well-known member
Joined
Mar 19, 2012
Messages
6,419
Location
Northern VA
Like many here, I have battery life anxiety to go along with my range anxiety!

Unlike most, I have an incentive to charge during the daytime rather than at night. The reason is that our solar array produces about 8 kW during the sunlight hours. There is a long run back to the meter from the array. While the microinverters produce 240 VAC and I used fairly large wire, I think there may still be a percent or so of voltage drop. So the plan has always been to feed the EV and the array from the same sub panel to eliminate losses in both directions. To my knowledge, our electricity provider does not offer time-of-use metering, so I have no incentive to charge at night from that angle.

But some anecdotal evidence I have read here makes me wonder if perhaps charging at higher ambient temperatures may adversely affect the life of the battery in the Leaf. Of course the charger is temperature compensated, but high temperatures do tend to have the effect of making things wear out more quickly.

So my question is this: Is there any reason to believe that I will get more life out of the battery pack by charging in the cool hours of the middle of the night versus during the heat of the day this summer?

A secondary question would be for winter: It does seem likely that charging during the warmest hours of the day would be more efficient than charging during the cold of the night in winter. Is that correct?

Finally, I'm wondering if I will get better battery life if I charge at a lower power. I understand that There is a fixed 100 W draw, so efficiency drops at lower charging power but will it be better for the battery? I will soon have the options here to charge at 120 V @ 12 A, 240 V @ 12 A or 240 V @ 16 A.

Please provide links to specific data for the Leaf battery or at least Li-ion information if you can.

TIA!
 
I have no idea. Given that you're in "Northern VA", high day-time temperature is probably not one of your concerns, and also not a concern with battery charging (thought that's pure conjecture on my part). I'd say you have far less to be concerned about than those of us in Arizona or Texas. During the summer here in Austin, it's not unusual for night-time low to be in the mid 80s.
 
RegGuheert said:
Like many here, I have battery life anxiety to go along with my range anxiety!

Unlike most, I have an incentive to charge during the daytime rather than at night...

OT- But, are you sure about that, that at no time in the future you will receive a TOU rate option, or that there are no benefits to night charging, beyond a preferred rate?

Virtually all American utilities, and the electric grids they connect to, experience their highest demand in the day, particularly on hot afternoons, due to demand for Air conditioning. They generally meet demand spikes by operating the most costly, least efficient (in terms of energy conversion) plants, typically low efficiency "peaker" natural gas plants.

So, while your rates may not reflect this (yet) you would almost certainly be reducing both the total CO2 output of the grid you connect to, and the total cost of providing electricity to all ratepayers, by charging at night, as it sounds like the marginal reduction in your own efficiency of electricity production and use, by night time charging, would likely be far less.

It's unfortunate that your utility does not have rates that reflect this reality, and provide you a fair return for the premium product you provide, peak demand kWh.

Most all BEV/PHEV drivers now face similar situations, with other failures of market signaling, as is the case when we are given the opportunity to replace paid off-peak charging at night with "free" public opportunity charging.

If you are plugging in during the day, when you could just as easily wait till you got home, to charge overnight, you are almost certainly imposing both short term economic costs on others, and long-term environmental costs, on everyone on the planet, present and future.

I am not trying to suggest what the correct action is to take in any of these situations, I'm just pointing out that your decision, may not always be based exclusively, on immediate cost considerations.
 
ok I have a side question, how did you manage a 9.87kw system in Northern Va with the limited tax credits
who did the install and is it leased or purchased?
 
aqn said:
I have no idea. Given that you're in "Northern VA", high day-time temperature is probably not one of your concerns, and also not a concern with battery charging (thought that's pure conjecture on my part).
In the summertime the high temperature can get to 105F during the day and 80F during the lowest part of the night. That doesn't happen every year nor will it last longer than a week or so in the years that it does happen. This year we have had the warmest winter that I can remember. If this trend continues into the summer, it will be a very hot year. I haven't measured the temperatures in our garage, but I imagine they are slightly moderated from the outdoor temperatures, although I am not sure.
aqn said:
I'd say you have far less to be concerned about than those of us in Arizona or Texas. During the summer here in Austin, it's not unusual for night-time low to be in the mid 80s.
Agreed I have less to be concerned about than those places, but my goal is to have this car for 20 years as our main runaround car with typical round-trip lengths ranging from 15 to 50 miles. Some of those trips require scaling a 1000-foot elevation twice and sometimes the trips will be made at 10F. I seriously doubt the car has the range to make the 50-mile trip with 2 mountain crossings at 10F today. Any reductions in range will eliminate some trips we could make, thus reducing the utility of our purchase.

Since I am a firm believer that charging is the main killer of batteries and we have nearly full control of when we charge, my intention is to charge at whatever times (temperatures) tend to give the best cycle life. Clearly there is a window of temperatures which is optimum for charging the Leaf to ensure the best battery life. I am trying to determine what that window is.
 
I was told by Nissan CS that charging at L2 (240v) is best. It's built for that. I have no idea on the best temperature to charge at, but I think as close to 70F is best (just my opinion); unfortunately that's not always possible as I usually have to charge while sitting outside.
 
RegGuheert said:
Since I am a firm believer that charging is the main killer of batteries
IMO - it's not the charging that is the main killer of batteries (certainly not at at the trickle charge L1/L2 rates) - it's storage of the car in high temperatures and high SOCs that is the killer. The higher the SOC of the battery during that time spent sitting at high temperature, the faster the battery will age.

Avoid charging to more than 80% unless you think you'll need the extra range and if charging to 100% time the charge so that it finishes as close as possible to departure time (it takes right around 90 minutes to go from 80-100% but the last 30 minutes the charge rate ramps down).
 
edatoakrun said:
OT- But, are you sure about that, that at no time in the future you will receive a TOU rate option, or that there are no benefits to night charging, beyond a preferred rate?
No, I am not. In fact, I am asking in this post whether there is benefit in terms of battery life in charging at night.
edatoakrun said:
Virtually all American utilities, and the electric grids they connect to, experience their highest demand in the day, particularly on hot afternoons, due to demand for Air conditioning. They generally meet demand spikes by operating the most costly, least efficient (in terms of energy conversion) plants, typically low efficiency "peaker" natural gas plants.
Here is a link to our electricity provider, Rappahannock Electric Cooperative (REC). I do not know what their demand curve looks like, but it seems to me that they have been taking rural customers off the hands of the larger utilities that no longer want to deal with them. If the great majority of REC's customers are rural, I would be not too surprised to see peak wintertime demand occur in the early hours of the morning when all the heat pumps and emergency resistive heaters are on. But I am sure you are correct that the peak demand during most of the year is during the daytime.
edatoakrun said:
So, while your rates may not reflect this (yet) you would almost certainly be reducing both the total CO2 output of the grid you connect to, and the total cost of providing electricity to all ratepayers, by charging at night, as it sounds like the marginal reduction in your own efficiency of electricity production and use, by night time charging, would likely be far less.
There are a lot of assumptions in what you say regarding how electricity is generated around here. Most of the base electricity generation comes from coal with some nuclear. While I do not know the exact make-up of peakers in the area, I do know that there is a 600 MW pumped-hydro peaker in VA. I'm pretty sure this peaker is used to allow the utilities time to bring coal power on and off-line. I'm not aware of any natural gas peakers in the region, but there may be some. We do not have natural gas lines in the immediate vicinity, but neither do we have power plants (except for a few solar arrays).

The point is that my electricity is produced by either coal or nuclear with peaking done using hydro. If we can more efficiently use the PV solar that we produce *and* more efficiently charge the EV that we have, then I have *reduced* the amount of electricity that I will consume overall and hence the amount of coal that is burned. And in either case this house will be a net producer during the daylight hours most days.
edatoakrun said:
It's unfortunate that your utility does not have rates that reflect this reality, and provide you a fair return for the premium product you provide, peak demand kWh.
We *just* got an electronic meter last June which is capable of tracking time of electricity usage, so I am hopeful that they will soon offer more attractive rate plans.
edatoakrun said:
Most all BEV/PHEV drivers now face similar situations, with other failures of market signaling, as is the case when we are given the opportunity to replace paid off-peak charging at night with "free" public opportunity charging.

If you are plugging in during the day, when you could just as easily wait till you got home, to charge overnight, you are almost certainly imposing both short term economic costs on others, and long-term environmental costs, on everyone on the planet, present and future.
I'm not sure whether you are referring to a singular or plural "you", but I am proposing to charge during the day in the wintertime and at night in summertime to try to improve battery life, both of which are possibly off-peak for my utility. I expect any improvements in battery life would have a very positive long-term effect on the environment.
edatoakrun said:
I am not trying to suggest what the correct action is to take in any of these situations, I'm just pointing out that your decision, may not always be based exclusively, on immediate cost considerations.
I hope you will agree that the essence of the question in this post pits the long-term cost, both to me and to society in general, of the battery against the short-term savings that I could gain by charging when the sun shines. It is all about conservation.
 
Since you have plentiful free electricity, why not air condition the garage where the Leaf sits while charging?

Since you are in this for the long run, instrument the battery case with a temperature sensor, then you will know how hot it gets.

I suspect many Leaf owners will be updating batteries as they evolve, whether they need to or not.. there will be lots of used batteries for sale. Its like a hobby :)

You have a high mix of nuclear power in your utility.. 38.6% nuke, 51.1% coal

This site will tell you:
http://www.epa.gov/cleanenergy/energy-and-you/how-clean.html" onclick="window.open(this.href);return false;
 
kmp647 said:
ok I have a side question, how did you manage a 9.87kw system in Northern Va with the limited tax credits
who did the install and is it leased or purchased?
To be honest, we purchased a kit on eBay and installed it. At the time we purchased, the plan was to sell SRECs to Washington, DC for about $0.25/kWh since they were allowing neighboring states to participate at that time. Between that, the federal tax credit and net metering, we expected the system would have paid for itself in 5 or 6 years and been cash positive after that. Unfortunately the SREC prices in Washington DC collapsed due to oversupply and they closed their borders last August. Oh, well.

We can still sell SRECs into PA, but those prices have also collapsed, so I expect they will also close their borders. If everything stays the same for the next 20 years, then I expect our system will just break even. But I think that is highly unlikely. It seems that the electricity market in VA is about to be deregulated, which will likely greatly increase prices if VA is anything like neighboring states. I also expect to benefit from TOU metering in the future.

Only time will tell, but experience tells me that this type of investment tends to pay off in untold ways. For instance, when we purchased our Honda Civic Hybrid ten years ago, gasoline cost $1.65/gallon. I did a calculation that I would need to drive 100,000 miles on $2/gallon gas to pay back the $4000 extra on the price tag. After 10 years and 90,000 miles, gasoline costs $3.75/gallon and the HCH is still going strong! I suppose the hybrid system has paid for itself at this point and will continue to pay benefits to us and the environment. We will see.
 
RegGuheert said:
After 10 years and 90,000 miles, gasoline costs $3.75/gallon and the HCH is still going strong! I suppose the hybrid system has paid for itself at this point and will continue to pay benefits to us and the environment. We will see.

Lots of anecdotes about failing Honda batteries.
 
coqui said:
I was told by Nissan CS that charging at L2 (240v) is best. It's built for that.
That's probably what I'll do. It certainly seems to be the most efficient charging rate given the ~100W load that goes along with charging the Leaf.
coqui said:
I have no idea on the best temperature to charge at, but I think as close to 70F is best (just my opinion);
I also suspect that is the sweet spot. In fact, 70F seems to be the sweet spot for most of the products we own!
coqui said:
unfortunately that's not always possible as I usually have to charge while sitting outside.
We are fortunate in that all of our charging should be done in the garage.
 
drees said:
IMO - it's not the charging that is the main killer of batteries (certainly not at at the trickle charge L1/L2 rates)
O.K. I agree it is not the charging, per se, but the overcharging that kills batteries. The issue lies with the lowest-capacity cells in the pack. I suppose we will eventually learn how effective Nissan's charging strategies are at preventing overcharge in any of the cells. Until we have many years of experience with these batteries and chargers I will assume that it is incumbent on us to baby our batteries if we want to achieve a very long life.
drees said:
- it's storage of the car in high temperatures and high SOCs that is the killer. The higher the SOC of the battery during that time spent sitting at high temperature, the faster the battery will age.

Avoid charging to more than 80% unless you think you'll need the extra range and if charging to 100% time the charge so that it finishes as close as possible to departure time (it takes right around 90 minutes to go from 80-100% but the last 30 minutes the charge rate ramps down).
Thanks! That is the kind of information I was hoping for!

Based on this information, it does seem like charging after midnight on hot days may be the best strategy to achieve maximum life. While I do not know the thermal time constant of the battery when installed in the Leaf, I will assume it is several hours in still air with all the fans off. The battery should be at its max temperature after a drive in the heat of the sun. On a 100-degree day, the battery likely will not get below 90 degrees before about midnight, so it makes sense to charge then to keep the peak temperatures as low as possible. This approach also will minimize the magnitude of the temperature excursions the battery sees and therefore the stresses associated with thermal cycling.

So what does everyone think about charging in the wintertime? Does it make more sense to charge on the heat of the day, say when the temperature is up to 35 or 40F? (And I mean from the perspective of battery efficiency and longevity.) This would increase the magnitude of the thermal cycling, but it seems Li-ion batteries don't do so well I the cold...
 
Herm said:
Since you have plentiful free electricity, why not air condition the garage where the Leaf sits while charging?
Good question! The answer is that we are still net consumers of electricity since we use it for space and water heating in our home. But I would certainly consider it if we were net producers given the SRECs are not available to us any longer.
Herm said:
Since you are in this for the long run, instrument the battery case with a temperature sensor, then you will know how hot it gets.
I absolutely plan to purchase a LeafScan once Phil releases them to us so that I can monitor battery pack temperatures, among other things!
Herm said:
I suspect many Leaf owners will be updating batteries as they evolve, whether they need to or not.. there will be lots of used batteries for sale. Its like a hobby :)
I agree the Leaf will be a very popular hobby EV! I also expect there may be some available due to wrecks. But my strong preference would be to try to make my batteries last as long as possible.
Herm said:
You have a high mix of nuclear power in your utility.. 38.6% nuke, 51.1% coal

This site will tell you:
http://www.epa.gov/cleanenergy/energy-and-you/how-clean.html" onclick="window.open(this.href);return false;
Thanks for the link! I would interpret that as a high mix of coal! ;)
 
"RegGuheert"...There are a lot of assumptions in what you say regarding how electricity is generated around here. Most of the base electricity generation comes from coal with some nuclear. While I do not know the exact make-up of peakers in the area, I do know that there is a 600 MW pumped-hydro peaker in VA. I'm pretty sure this peaker is used to allow the utilities time to bring coal power on and off-line. I'm not aware of any natural gas peakers in the region, but there may be some. We do not have natural gas lines in the immediate vicinity, but neither do we have power plants (except for a few solar arrays).

The point is that my electricity is produced by either coal or nuclear with peaking done using hydro...

I think you may want to reconsider the conclusion above.

The entire east coast shares a single interconnected grid. The types of generation employed by your utility, or your region, do not determine the actual marginal generation that your Solar KWH production displaces, which will I believe, in fact be largely by NG fueled peaker plants, in the future, as it is today. And the proportion of coal-fired base load production, during the night, is almost certain, to continue to decline, in the future.

You are correct that it is a complicated analysis to try to minimize the most efficient use in your situation, and I did not, comment on your OP topic about battery aging benefits to day/night charging, since I am unqualified, to say more than that I doubt there really is data available, to provide an answer to your question.

But I think the far greater uncertainty is of the value of other costs and benefits, even if you could find an answer to your OT question.

The adverse effects of producing your present battery pack is a sunken cost.

IMO, you really need to be asking what the environmental and/or monetary cost will be to replace your Battery Pack, slightly sooner or later, in the next five, ten, or fifteen years, and what the residual value of the battery will be, when repurposed for other uses, at that time?

It may well prove that if the miles you (and future owners, if you ever sell) drive each year are not very high, and especially if all the owners carefully manage battery use, in other ways, calendar aging will be a far greater factor, than charging temp, rendering the question of battery charging temperature, insignificant.

And there are many other occurrence, such as damage to the battery pack, due to road accident or another cause, or improvement in battery technology, making either our present cars or battery packs obsolescent, before additional battery degradation becomes a factor, that would make all attempts to manage charge temperature by time-of-day, to reduce battery degradation, useless.

So I think most of the prospective future benefits you mention, off on-peak charging are probably far less certain, than the current benefits of off-peak charging.

For many, the overwhelming question, would actually be the lack of utility that daytime charging requires.

Does your schedule permit you to give up the option of driving, both regularly and/or on short notice, during the daytime?
 
Herm said:
Lots of anecdotes about failing Honda batteries.
That may be so, but we couldn't be happier with our HCH. We intend to keep it for many more years. Here's hoping!

I'm not sure I am allowed to say this on this forum, but I strongly expect there will be lots of anecdotes about Nissan Leaf batteries "failing" going forward.

Why? For a few reasons:

1) The battery in the Leaf tends to be on the low end of many customers needs and desires.
2) 1) above leads to unreasonable expectations and therefore disappointments.
3) 1) also leads to high DOD on a daily basis which will tend to reduce the life of the batteries.
4) Those same customers will find that the Leaf no longer meets there needs if the capacity drops even by a fairly small margin.
5) I do not feel that Nisan has done a good job of setting expectations for the capacity of the Leaf. Yes, it is all there in the warrantee and the disclaimer that we all signed, but reading it and living it will be VERY different things for most people, particularly when they realize what the resale value of their first-generation EV with a degraded batery is in the presence of many second- and third-generation EVs.
6) A Leaf battery which has degraded to the point to which it no longer meets the needs of its owner will be deemed a "failure" by that owner.
 
I suspect we are in violent agreement on most points, edatoakrun. Here are a few additional points:
edatoakrun said:
And the proportion of coal-fired base load production, during the night, is almost certain, to continue to decline, in the future.
It will take some major convincing for me to accept this statement. Coal production in this part of the world has been growing exponentially for decades and I fully expect that trend to continue for at least the next decade. I can't conceive of NG or nuclear growing at a faster rate and other candidates are too small to really consider. I believe coal's fraction will drop in the far future, but that will likely be after we no longer have the leaf.
edatoakrun said:
The adverse effects of producing your present battery pack is a sunken cost.

IMO, you really need to be asking what the environmental and/or monetary cost will be to replace your Battery Pack, slightly sooner or later, in the next five, ten, or fifteen years, and what the residual value of the battery will be, when repurposed for other uses, at that time?
i agree the issue here is the cost of a replacement combined with the environmental damage associated with disposal of the existing battery. Personally, I am very dubious of claims that these batteries will be repurposed. Sure, a few might be, but I predict that the vast majority will either be recycled or disposed.
edatoakrun said:
It may well prove that if the miles you (and future owners, if you ever sell) drive each year are not very high, and especially if all the owners carefully manage battery use, in other ways, calendar aging will be a far greater factor, than charging temp, rendering the question of battery charging temperature, insignificant.
Do you think it is unreasonable to get 150,000 miles out of this battery over 20 years and still be able to make 40-mile excursions? I'm not questioning, but rather I am interested to hear your, or others', opinions.
edatoakrun said:
And there are many other occurrence, such as damage to the battery pack, due to road accident or another cause, or improvement in battery technology, making either our present cars or battery packs obsolescent, before additional battery degradation becomes a factor, that would make all attempts to manage charge temperature by time-of-day, to reduce battery degradation, useless.
Agreed except that I don't think future battery technology really impact what we do with this car. In my opinion, if it meets our needs, it meets our needs, regardless of what else comes along. If it fails to meet our needs, then that is a different story.
edatoakrun said:
So I think most of the prospective future benefits you mention, off on-peak charging are probably far less certain, than the current benefits of off-peak charging.
This is the main point and I belief you are correct. I still may consider daytime charging during the colder winter days.
edatoakrun said:
For many, the overwhelming question, would actually be the lack of utility that daytime charging requires.

Does your schedule permit you to give up the option of driving, both regularly and/or on short notice, during the daytime?
I would say yes. Since our excursions tend to be short I am even considering charging every other day instead of every day. We'll see how that flies given that my wife already has rather severe range anxiety. (The longer excursions over the mountain are almost always scheduled, so we can plan for them.)
 
RegGuheert said:
I suspect we are in violent agreement on most points, edatoakrun. Here are a few additional points:
edatoakrun said:
And the proportion of coal-fired base load production, during the night, is almost certain, to continue to decline, in the future.
It will take some major convincing for me to accept this statement. Coal production in this part of the world has been growing exponentially for decades and I fully expect that trend to continue for at least the next decade...

Just another thread you might want to look at, as it is a major point in your analysis I'd question:

Quote:

By Joe Romm on Mar 12, 2012 at 11:10 am

The U.S. Energy Information Administration reported on Friday:

… coal’s share of monthly power generation in the United States dropped below 40% in November and December 2011. The last time coal’s share of total generation was below 40% for a monthly total was March 1978. A combination of mild weather (leading to a drop in total generation) and the increasing price competitiveness of natural gas relative to coal contributed to the drop in coal’s share of total generation.

http://www.mynissanleaf.com/viewtopic.php?f=7&t=7451&hilit=+natural+gas&start=30" onclick="window.open(this.href);return false;

IMO, even if there is never a price placed on CO2 pollution, NG will probably continue to replace coal, at least until large scale NG export facilities are built.

And in base-load operation, the NG plants are generally very efficient combined cycle plants, unlike NG peaker plants, which are built as cheaply as possible, to allow for economic operation, amortized over fewer hours of use, each year.
 
RegGuheert said:
Do you think it is unreasonable to get 150,000 miles out of this battery over 20 years and still be able to make 40-mile excursions?
I'm not a battery expert, but I'm guessing you'd be hard pressed to get that much at 150K AND 20 years. Maybe one or the other, and 20 years seems a little long. Things I've ready indicate that once the battery starts to degrade past a certain point, it will rapidly decline.

40 miles is my threshold for being a "usable" car. My wife's commute is just over 30 miles, so when it hits 40 miles of range it's going to be time to upgrade. If the price of batteries stays above $5K, I'd be inclined to wait until we hit that threshold. If it drops below $5K, I might consider replacement earlier (particularly if there is a good "trade-in" deal for grid-storage use). And who knows...maybe I'll feel the car has become obsolete at that point anyway and sell it as a used car. At any rate, I would hope that I would get 150K-200K miles before that point, 8-10 years (because we drive the LEAF everywhere we can and are effectively replacing 2 cars with it, we're actually on a 20K/year pace).
 
Ed

IMO, you really need to be asking what the environmental and/or monetary cost will be to replace your Battery Pack, slightly sooner or later, in the next five, ten, or fifteen years, and what the residual value of the battery will be, when repurposed for other uses, at that time?
"RegGuheert"i agree the issue here is the cost of a replacement combined with the environmental damage associated with disposal of the existing battery. Personally, I am very dubious of claims that these batteries will be repurposed. Sure, a few might be, but I predict that the vast majority will either be recycled or disposed.
edatoakrun said:
It may well prove that if the miles you (and future owners, if you ever sell) drive each year are not very high, and especially if all the owners carefully manage battery use, in other ways, calendar aging will be a far greater factor, than charging temp, rendering the question of battery charging temperature, insignificant.
Do you think it is unreasonable to get 150,000 miles out of this battery over 20 years and still be able to make 40-mile excursions? I'm not questioning, but rather I am interested to hear your, or others', opinions.
edatoakrun said:
And there are many other occurrence, such as damage to the battery pack, due to road accident or another cause, or improvement in battery technology, making either our present cars or battery packs obsolescent, before additional battery degradation becomes a factor, that would make all attempts to manage charge temperature by time-of-day, to reduce battery degradation, useless.

"RegGuheertAgreed except that I don't think future battery technology really impact what we do with this car. In my opinion, if it meets our needs, it meets our needs, regardless of what else comes along. If it fails to meet our needs, then that is a different story.

I think the single answer (more or less) to these questions, is that the most "re-purposing" of LEAF battery packs will occur by passing on the entire car, to another driver, at the point the battery capacity drops below that required to give the range necessary, to the individual LEAF owner.

In my case, that is about 80%-90% of my present, ABC, assuming I want to continue to avoid the inconvenience and/or cost of interim charging, on my most common daily 50-60 mile "commute".

So, I am trying to manage battery degradation, as best as I can, given the limited information available.

But, I expect that, rather than replacing the battery when, (I hope, towards the latter extremes, of five to ten years, and 50,000 to 100,000 miles) I will sell my LEAF to a buyer, who will find the less-than-new battery capacity, as well as the less--than-new-condition, of the rest of the car, adequate for their needs.
 
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