sproqitman
Well-known member
I live in an area with some relatively steep (8% to 15%), but short hills. As long as I'm not trying to show off, I can keep the power demand in the 3-4 bubble range (< 20 KW).abasile said:
Ways to preserve battery capacity (besides charging to 80%)?
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Herm
Well-known member
abasile said:
I agree with you and would add also to move out of Phoenix ASAP.. in any case Nissan is giving a good deal on the lease program.
ERG4ALL
Well-known member
We've had our LEAF for two days now and I have a question more seasoned owners may be able to answer. I have set Timer 1 to 80% and have trickle charged overnight. How can I tell that it really charged to 80%, all of the range bars still show? The dealer seems to think that even though it is at 80% the bars are indicating a full charge to what was requested. This does not seem logical to me. I would prefer to see something like 9 out of 12 bars showing. That way a bar always means the same thing whether you charge to 80% or 100%.
Another question is, having read the manual on charging and most of the posts here, it goes without saying that an 80% top charge is best for the battery and it also is good not to exhaust the battery to "--" miles showing. My question is, does it do any harm to "top off" to 80% each night regardless of whether the battery is indicating 70% charge remaining or something lower? Some seem to think that it is better to cycle the battery deeper before recharging. The problem with that is that you may run errands during the morning and then want to "top off" because you are going to be driving at night out to dinner and using the A/C at the same time.
Another question is, having read the manual on charging and most of the posts here, it goes without saying that an 80% top charge is best for the battery and it also is good not to exhaust the battery to "--" miles showing. My question is, does it do any harm to "top off" to 80% each night regardless of whether the battery is indicating 70% charge remaining or something lower? Some seem to think that it is better to cycle the battery deeper before recharging. The problem with that is that you may run errands during the morning and then want to "top off" because you are going to be driving at night out to dinner and using the A/C at the same time.
abasile
Well-known member
That is a very good question! I'd certainly like to know the answer as well. Can anyone with good knowledge of Li battery chemistry enlighten us?ERG4ALL said:
DarkStar
Well-known member
Depending on the battery management, it shouldn't matter at which point you start charging. If it was a NiMh or NiCad battery, it would definitely be wise to discharge the battery prior to a complete charge (memory effect), but LiPo or LiFePO4 batteries don't experience the same memory effect issue, excess over-charging/over-discharging will have a much more profound effect though (but shouldn't be possible due to the battery management system).abasile said:
LEAFer
Well-known member
If you charge to 80% 10 bars will be lit. And if you are getting notifications .. after the car has completed the timed charge it will say
If you charge to 100% ... at completion the notification will be
(blue color is my emphasis of an interesting difference)
If you charge to 100% ... at completion the notification will be
(blue color is my emphasis of an interesting difference)
planet4ever
Well-known member
This goes directly to the issue of cycle count. Is the battery life really measured in number of cycles? Or by the frequency of exceeding the mid-range? Or by maximum charge/discharge rate? Or perhaps by the total kWh pumped into it over its life? Or (most likely) some combination of these? But ERG4ALL has asked this question in its simplest form, and as someone who expects to average 20 to 30 miles per day, with many days at 10 miles or less, I'd really like to hear some expert opinions.ERG4ALL said:
Ray
AndyH
Well-known member
From the viewpoint of battery manufacturer and testing, cell/battery life is measured in cycles until 80% of capacity remains. A 'cycle' is completely emptying and then recharging the cell/battery. Starting at 100% charged, driving until the car stops, and then recharging completely is one cycle.
If we have a 2000 cycle lifespan on the pack, we can do that with 2000 days of 100+ mile travel. 10,000 work days with a 20 mile round trip is also 2000 cycles, as is 500 days of 400 mile travel (with four L3/DC charges each day).
Lithium doesn't have a memory and doesn't care how often it's charged...or not. As long as the BMS does its job, and as long as the car isn't stored in a 140°F garage at 100% fully charged for years, it doesn't matter much how or when you charge.
If we have a 2000 cycle lifespan on the pack, we can do that with 2000 days of 100+ mile travel. 10,000 work days with a 20 mile round trip is also 2000 cycles, as is 500 days of 400 mile travel (with four L3/DC charges each day).
Lithium doesn't have a memory and doesn't care how often it's charged...or not. As long as the BMS does its job, and as long as the car isn't stored in a 140°F garage at 100% fully charged for years, it doesn't matter much how or when you charge.
ttweed
Well-known member
Andy,AndyH said:
As someone who has little experience in battery technology or EVs, I have to say how much I appreciate the information you and other seasoned, knowledgeable individuals contribute to this forum. It is invaluable to me as I try to educate myself in preparation for taking the long-awaited delivery of my new car.
Thank you, and everyone else who contributes to this knowledgebase.
TT
DeaneG
Well-known member
General question: is it fair to say that assuming a fixed driving efficiency of say 3.5mpk, that a battery life in terms of full cycles is also roughly measurable as a battery life in terms of miles? That is, the Leaf's battery would not care about depth of discharge or number of charge/discharge cycles within the 80% capacity, but only how many electrons ebb and flow in total through the battery's life.
For the Leaf, say that 2000 80% "cycles" at say 18kWh each reduce battery capacity to 80% of new. Is it fair to state this as roughly 2000 cycles * 18kWh * 3.5mpkWh = 126,000 miles to 80% capacity?
For the Leaf, say that 2000 80% "cycles" at say 18kWh each reduce battery capacity to 80% of new. Is it fair to state this as roughly 2000 cycles * 18kWh * 3.5mpkWh = 126,000 miles to 80% capacity?
Yeah, you boffin types are cool! 
I'm still gonna do what I gots to do, but I'm happy to get some estimation of what that will cost me over the long term.
I'm still gonna do what I gots to do, but I'm happy to get some estimation of what that will cost me over the long term.AndyH
Well-known member
That's my general impression. There's calendar aging as well. We'd need more specifics from Nissan/AESC to get better info than TLAR engineering (that looks about right).DeaneG said:
This is rapidly getting outside my area as I'm not a chem-E or materials person.
AndyH
Well-known member
My pleasure, Tom. I'm glad the time spent destroying cells and getting abused by management systems is paying off. :lol:ttweed said:
linkim
Well-known member
While we wait for our LEAF, we can humor (educate) ourselves by reading the blogs by my friend Dr. Srinivasan at Lawrence Berkeley National Laboratory. Read his blog for his view on capacity fade:
http://thisweekinbatteries.blogspot.com/2010/11/if-your-cat-has-nine-lives-shouldnt.html
There is another factor to consider besides SOC, temperature etc., and that is calendar life. That is, how long will the battery last with and without cycling? If the battery is kept at high SOC when the vehicle in not in use (assume temperature is not a factor), then the calendar life will be shorter than a vehicle battery kept at lower SOC when not in use. In between, the battery in use is charged-discharged by regen and by connecting to a plug. So my take on all of this is that there is no simple answer to the question DeanneG asked. However, the warranty on the LEAF battery is 8 years so hopefully that is some assurance that calendar life is not an issue.
http://thisweekinbatteries.blogspot.com/2010/11/if-your-cat-has-nine-lives-shouldnt.html
There is another factor to consider besides SOC, temperature etc., and that is calendar life. That is, how long will the battery last with and without cycling? If the battery is kept at high SOC when the vehicle in not in use (assume temperature is not a factor), then the calendar life will be shorter than a vehicle battery kept at lower SOC when not in use. In between, the battery in use is charged-discharged by regen and by connecting to a plug. So my take on all of this is that there is no simple answer to the question DeanneG asked. However, the warranty on the LEAF battery is 8 years so hopefully that is some assurance that calendar life is not an issue.
charlie1300
Well-known member
So what I'm getting out of this discussion is the two major components of capacity loss relate to the total number of charge cycles, and charging to full capacity and discharging to completely empty.
In my particular situation, which I don't think is uncommon, I expect to use 30% to 40% of the battery capacity per day. That gives me two choices:
1. Charge to 100% every other day, reducing the total number of charge cycles.
2. Charge to 80% every day, staying more in the middle of the battery capacity.
Anyone want to offer an opinion which is a better method to preserve battery capacity?
In my particular situation, which I don't think is uncommon, I expect to use 30% to 40% of the battery capacity per day. That gives me two choices:
1. Charge to 100% every other day, reducing the total number of charge cycles.
2. Charge to 80% every day, staying more in the middle of the battery capacity.
Anyone want to offer an opinion which is a better method to preserve battery capacity?
linkim
Well-known member
Given the two options, I would do #2 and avoid the very high SOC. The Li-ion battery is most susceptible to degradation at high SOC so I plan to minimize exposure of the battery to high SOC. Obviously, if I need to use the LEAF for a longer trip that requires charging to high SOC, then I will do so.
AndyH
Well-known member
Charlie, you have plenty of other choices. Let's start with a 'cycle' though. Charging to 100% isn't a cycle so there's no need to hold back if you need to charge to 100%.charlie1300 said:
If you charge to 100%, then drive a 100 mile round-trip, and recharge to 100%, that's pretty close to 1 cycle.
If you charge to 100% Sunday night, then drive 20 miles each day from Monday to Friday, and recharge to 100% Friday night, that's also about 1 cycle.
If you charge to 80% Sunday night, then drive 20 miles each day Mon-Wed, when you arrive home Wednesday you'll have used about 60% and have 20% left. If you recharge to 80% Wednesday night and then drive 20 miles Thursday and Friday, and then recharge to 100% Friday night, you'll also have used about 1 cycle.
So - you can charge to 80% every day, or charge to 80% every couple of days, or charge to 100% every couple of days, or any combination that gets you where you want to go without resorting to a flatbed.
I hope that helps...
DaveinOlyWA
Well-known member
thanks for explanation Andy. charge cycles is something that is alien to most since its not how they equate the definition.
its like filling the gas tank. whether you fill it when its just above empty or fill it at 3/8th of a tank, its still full but the $10 (ummm make that $15) difference in the cost of gas is hard to ignore.
so look at "charge cycles" being a dollar amount to spend with a dime surcharge added for each "fillup".
likewise with the battery capacity. if you only need 20-30 miles on a daily basis, charge to 80% DAILY. because there will be times when you will need more than your normal range and not being prepared for those days will create a negative ownership experience.
its like filling the gas tank. whether you fill it when its just above empty or fill it at 3/8th of a tank, its still full but the $10 (ummm make that $15) difference in the cost of gas is hard to ignore.
so look at "charge cycles" being a dollar amount to spend with a dime surcharge added for each "fillup".
likewise with the battery capacity. if you only need 20-30 miles on a daily basis, charge to 80% DAILY. because there will be times when you will need more than your normal range and not being prepared for those days will create a negative ownership experience.
charlie1300
Well-known member
Thanks for the explanation, Andy. Just to make sure I've got the concept right, in terms of charge cycles, what you are saying is that my two options actually have the same number of charge cycles.
DaveinOlyWA
Well-known member
charlie1300 said:
yes they do, but charging to 100% increases the potential to lose some battery capacity and charge cycles. 80% not only eliminates overcharging caused by temperature changes, but also helps to extend total battery life by keeping it within the optimum charging range.
basically, the ONLY drawback to keeping the battery at an SOC between 40-80% (which you would be in if charging daily) is the reduction in range.
what we want eventually is opportunity charging EVERYWHERE we go. Fred Meyer adding charging location i can only hope is a business model that will be incorporated into every parking lot, public and private. this allows a bump charge thru-out the day and keeps us in that middle SOC range but allows us to drive nearly as much as we want to
