Joining the 80% Club

[TomT]

Nissan has given no indication that going below 20% has any affect on battery life or capacity whatsoever and if it did, I'm sure they would have said something. Their only admonishments are that charging to 100 percent regularly, using frequent QCs, and leaving the battery for an extended time at 100% negatively affect battery capacity... Thus, I see no reason to worry about the bottom 2 bars (or 4, depending on how you interpret the gauge)...

 

[davewill]

Nissan has given no indication that going below 20% has any affect on battery life or capacity whatsoever and if it did, I'm sure they would have said something. Their only admonishments are that charging to 100 percent regularly, using frequent QCs, and leaving the battery for an extended time at 100% negatively affect battery capacity... Thus, I see no reason to worry about the bottom 2 bars (or 4, depending on how you interpret the gauge)...

...and they suggested not recharging if you don't run the battery below 80%. I've taken all this to mean that opportunity charging to 80% is acceptable regardless of how much (or little) I've run the battery down. I charge to 100% if I expect to venture much into the last two bars, but that's for my peace of mind, not to "save" the battery.

 

[surfingslovak]

I wish the car had about 25% more capacity. This would let me do nearly all my normal trips on a 80% charge and a few more on a 100% charge without having to worry about range.

Interesting read, thank you for sharing. Yes, I wonder what it would take to add about 20 miles of range to the Leaf. Once again, we can only speculate, but I think that this would translate to about 12 additional modules, 100 pounds of extra weight and $6K at retail prices (assuming $500 per module). I think that it's doable even with today's technology and I would do it in a heartbeat had Nissan offered this option. This would increase the utility of the car and ironically decrease the wear and tear on the battery and likely extend its projected life as well.

 

[DaveEV]

Nissan has given no indication that going below 20% has any affect on battery life or capacity whatsoever and if it did, I'm sure they would have said something. Their only admonishments are that charging to 100 percent regularly, using frequent QCs, and leaving the battery for an extended time at 100% negatively affect battery capacity... Thus, I see no reason to worry about the bottom 2 bars (or 4, depending on how you interpret the gauge)...

...and they suggested not recharging if you don't run the battery below 80%. I've taken all this to mean that opportunity charging to 80% is acceptable regardless of how much (or little) I've run the battery down. I charge to 100% if I expect to venture much into the last two bars, but that's for my peace of mind, not to "save" the battery.

Exactly.

I wish the car had about 25% more capacity. This would let me do nearly all my normal trips on a 80% charge and a few more on a 100% charge without having to worry about range.

Interesting read, thank you for sharing. Yes, I wonder what it would take to add about 20 miles of range to the Leaf. Once again, we can only speculate, but I think that this would translate to about 12 additional modules, 60 pounds of extra weight and $6K at retail prices (assuming $500 per module). I think that it's doable even with today's technology and I would do it in a heartbeat had Nissan offered this option. This would increase the utility of the car and ironically decrease the wear and tear on the battery and likely extend its projected life as well.

Yes - a slightly bigger pack combined with a couple of easily adjustable charge limits (say 70%-80%-90%-100%) would easily let one keep the pack in the middle of the SOC range which should improve battery life. How much? As long as it's measurable you can bet the EV geeks in us will do it even if not substantially significant.

 

[Devin]

Here's another use case to throw into the pot...

I have TOU and L2 at home and the low cost charging times are Mon-Fri 8PM-10AM, all day weekends. I also have completely free L1 at work. My route is 12.8 miles to work with and 13.9 miles home with an elevation difference of 410' (work is downhill). During the weekends I frequently drive much farther than during the week.

Currently I charge to 80% on the weekends starting with L2 Friday night and any time I get back home during the weekend. If I am going to drive further and want 100% range I try to start a charge from 80%-100% strategically so the car is fully charged for no more than 30 minutes before leaving.

At work I try to set an L1 charge to 80% every day that ends in the evening between 7 and 8PM before I usually leave work. I used to charge to 80% immediately upon arriving at work but changed to stack that towards the end of the day so the car sits longer around 50% SOC but also because my parking spot is shady in the afternoon and sunny in the morning so the car will be cooler during charging.

Sometimes though this strategy will put me at home with about 3-5 bars left if I detour to make additional stops on my way home. I could make it to work with that much power (I can usually get there on 1 bar, 2 at most) but I generally figure it is better to L2 to 80% at home in that case and resume the schedule the next day rather than dip that low into the pack.

If I have to do a longer journey during the week with most driving in the morning I'll charge overnight L2 to 100%, if it's in the evening I charge at home to 80% and charge to 100% via L1 while at work.

Last week I had a doctors appointment in Newbury Park in the morning so I L2ed to 100% at my house, stopped at my parent's house in Agoura (26 miles) and used their L2 from 9 bars to 11 bars. I then drove to Newbury Park for the appointment and from there to my office (55 miles) and L1ed to 80% again. I could have made it from my home to Newbury Park and then to my office without charging additionally in between but I wanted to have breakfast with my dad.

So that's 3 charges in a day, 12/100%, 11/~90%, then 10/80% which I figure is about as harsh on the battery as two charges to 100%. In the future I could do this trip the same way but instead do charges to 10/80%, 10-11/80-90%, and 10/80% by leaving home slightly earlier but I'm not so sure that would make that much of a difference in battery longevity? Would a better situation (battery wise) be to skip my parents and just do 100% in the morning to take me the 80 mile trip to work via Newbury Park? That would use a much larger SOC range of the battery but involve fewer charging events.

 

[surfingslovak]

Hi Devin, interesting use case. My first reaction would be, skip charging at your parents house, and charge at your doctor's office if possible. Even if it was just a trickle. I'll give it some more thought, and perhaps others will chime in as well. How often do you do this trip?

 

[TomT]

I do the same. I charge to 100 percent when I think I will need the extra range, otherwise 80 percent whenever I have the opportunity... I don't worry about how far I might go in to the bottom portion of the battery.

... and they suggested not recharging if you don't run the battery below 80%. I've taken all this to mean that opportunity charging to 80% is acceptable regardless of how much (or little) I've run the battery down.

 

[Devin]

Hi Devin, interesting use case. My first reaction would be, skip charging at your parents house, and charge at your doctor's office if possible. Even if it was just a trickle. I'll give it some more thought, and perhaps others will chime in as well. How often do you do this trip?

Roughly ever 3-4 months. Unfortunately the doctors office parking lot is always crowded and while I didn't look too hard I didn't see any sockets for L1 charging opportunities. I'll ask my doctor about talking to the facility to get them to consider installing EVSEs when I go for my next appointment. It would make a lot of sense to do in that location since it is a pretty large complex, here's their website: http://losrobleshospital.com/

 

[surfingslovak]

I'll ask my doctor about talking to the facility to get them to consider installing EVSEs when I go for my next appointment. It would make a lot of sense to do in that location since it is a pretty large complex, here's their website: http://losrobleshospital.com/

I sounds like it would be ideal to charge there, and I would surprised if you were the only one requesting it. I wouldn't worry about the battery too much if this is not a trip you would do a frequent basis.

 

[Devin]

I'll ask my doctor about talking to the facility to get them to consider installing EVSEs when I go for my next appointment. It would make a lot of sense to do in that location since it is a pretty large complex, here's their website: http://losrobleshospital.com/

I sounds like it would be ideal to charge there, and I would surprised if you were the only one requesting it. I wouldn't worry about the battery too much if this is not a trip you would do a frequent basis.

I'm not too worried about the battery for the specific trip since I don't make it that often. I am interested in the effects in an academic sense though as I can picture having similar situations pop up with greater frequency now that the charging infrastructure is starting to spread.

 

[AndyH]

What type of cell/battery reports did you find, what specific chemistry, and in what applications did you use to arrive at this management plan?

Andy, I wouldn't call it a management plan. I simply stuck my neck out and tried to put a number or two in the sand. There is so much angst out there and I thought that it would be helpful.

I don't expect Nissan to come out with a battery care guide anymore. They consider so many aspects of the Leaf to be proprietary and confidential, that they won't say anything, even if it translated to poor customer service. In the light of this, and until someone thoroughly examined a few Leaf battery modules, everything we say is speculation and a matter of opinion.

I would hope that the smart and knowledgeable people on this forum could agree on a consensus for battery care, something we would feel comfortable recommending to other owners, even though it was just an educated guess.

But back to your question. The numbers I used in the post you quoted were based on a JPL report for the Mars rover mission. They found the capacity fade from cycling to be about six times higher at 60% DOD when compared to 30% DOD. They used SAFT LiNiO2 cells with graphite anode and cylindrical stainless steel hardware. The cells were tested in 30% DOD regime (5000 cycles) with average energy fade rate at 4.0V at 0.000704% per cycle and 60% DOD regime (500 cycles) with average energy fade rate at 4.0V at 0.00430% per cycle.

I also found the Tesla battery care guide from Dan Myggen to be of interest. I believe that the Roadster is using 18650 form-factor LiCoO2 cells. I don't claim to be the world's foremost expert on lithium ion cells, but this is an important topic and I would love to continue the discussion. I'm not sure if this is the right venue though, this thread is already 24 pages long.

Thanks very much. I really do understand why folks are trying to 'define the beast' one way or another. And I've certainly been foisted after my own mind has tried to fill-in an information vacuum and made a mess. But as I and others have written on this forum in a number of places. bad data is worse than no data, and is is not safe to assume that we're helping to close a knowledge gap by bringing in bits of information from many different cell types or from different applications.

Best info we have about the raw cells comes from AESC. Best info we have on the car and its systems comes from Nissan (and there's good info in the service manual about cell and battery voltages and how the battery is managed. This is the best info we have for our 'target bullseye' at the moment (as you've already recognized). Moving toward the outer target rings, we'd have other data from manufacturers making the exact same chemistry (I don't know of any). Then info on other LiMn variants. Then info on other Li variants. Then, and only then, and only for those that want to compare/contrast, one might include info from other cell types - like NiCd, NiMH, lead acid, etc. But I think it's very important to remember that the only reliable info we have is that from AESC and Nissan.

I believe the information people are looking for has already been posted on this forum. Yes - I realize that takes the fun out of those that prefer to talk things to death rather than search and filter, though.

Good Hunting.

 

[surfingslovak]

I believe the information people are looking for has already been posted on this forum. Yes - I realize that takes the fun out of those that prefer to talk things to death rather than search and filter, though.

Good Hunting.

Andy, if you don't mind, where specifically has this information been posted, what exactly is Nissan telling us? There is precious little information available and this forum, against better judgement, does not have an FAQ. This is precisely what's needed to avoid 26-page long threads. As it stands, we'll have to agree to disagree, and while I appreciate your critique, rest assured that I do my research thoughtfully.

I realize that you likely have more hands-on experience with li-ion packs than most of us will ever have, and if you wanted to put an FAQ together and put this thread to rest, please do. I think that every new owner will thank you. In fact, that's what I've been hoping for, a little more collaboration and less confrontation and ego stroking.

 

[TonyWilliams]

Type: Laminated lithium-ion battery
Total capacity (kWh): 24
Power output (kW): Over 90
Number of modules: 48

Battery pack contents:
-Positive electrodes – Lithium manganate
-Negative electrodes – Carbon

Fully charged @ 394V / 4.10v per cell

Nissan Motor Co. has nearly completed development of a lithium-ion battery using a lithium nickel manganese cobalt oxide cathode (NMC). The new system, which will reportedly offer almost double the capacity of Nissan/AESC’s current manganese spinel cell, is supposedly slated for deployment in electric vehicles in 2015.

Nissan is raising capacity by improving the positive electrode, specifically, using nickel and cobalt, not only manganese. The new battery can store about twice as much electricity as batteries with positive electrodes made only from manganese. It is robust enough for practical use, able to withstand 1,000 or so charge cycles.

Nissan estimates that the battery will cost about the same as conventional lithium ion ones to produce, as it contains only a small amount of cobalt, a relatively expensive metal.

 

[ttweed]

It is robust enough for practical use, able to withstand 1,000 or so charge cycles.

I thought I remembered seeing 3,000 cycles for the current battery--isn't 1,000 quite a bit less robust? Double the capacity for the same price would be nice, but 1/3 the life cycle would not.

TT

 

[TomT]

But from a practical perspective, if it has nearly twice the capacity, I would only need to recharge half as often (or even less), so it would come out close to a wash... Plus, it would allow me to do things I can not currently do with the Leaf...

That four year lease is looking better and better!

It is robust enough for practical use, able to withstand 1,000 or so charge cycles.

I thought I remembered seeing 3,000 cycles for the current battery--isn't 1,000 quite a bit less robust? Double the capacity for the same price would be nice, but 1/3 the life cycle would not.

 

[thankyouOB]

1000 charges seems like less than four years to me, unless they mean full cycles.
I currently charge 5-6 times a week = 250-300 a year.

 

[DaveinOlyWA]

1000 charges seems like less than four years to me, unless they mean full cycles.
I currently charge 5-6 times a week = 250-300 a year.

when referring to charge cycles, they always mean "full cycles". now if a battery is rated at 24 kwh. then 6 charging sessions of 4 kwh each would be one cycle.

 

[Volusiano]

Isn't the current battery rated at 24 kwh as well? OK, so if the new battery is still rated at 24 kwh, then you can't say that it has double the capacity of the existing one. Maybe you can say it has twice the energy density of the existing one, so it can be half the size and weight, but 24 kwh is still the same capacity as the existing one. So you still can't go further than the current 100 mile range on 24 kwh. Maybe a little bit more due to less weight, but that's all

Now if the existing one can hold 3000 full charge cycle like someone said, and this one holding only 1000 charge cycle, then at the same capacity of 24 kwh, the new one is only going to last 1/3 as long as the old one.

So advantages of new battery: Half weight, half size
Disadvantage: 1/3 life
Comparable: same cost, same capacity (24 kwh), same range (100 miles)

 

[DaveinOlyWA]

Isn't the current battery rated at 24 kwh as well? OK, so if the new battery is still rated at 24 kwh, then you can't say that it has double the capacity of the existing one. Maybe you can say it has twice the energy density of the existing one, so it can have double the capacity for the same size and weight. But if its rating is 24 kwh, then maybe it's half the size and weight and perhaps cost, but 24 kwh is still the same capacity as the existing one.

correct you CANT say it has double the capacity nor can we say it has twice the density either since the pack is most likely going to be about the same size and weight. but you can say it has twice the expected longevity.

but its like free refills of soda at a fast food joint. now why anyone would order a large when they plan to dine in is beyond me unless they are so fat and lazy they do not want to get up to make multiple trips to the soda fountain.

either way, the cup is the same size whether you refill it or not

 

[Volusiano]

[but you can say it has twice the expected longevity.

Not sure that I would agree with this.

Old battery pack: 24 kwh * 3000 cycles = 72,000 kwh total life, assuming each 24 kwh yields 100 miles: = 300K miles
New battery pack: 24 kwh * 1000 cycles = 24,000 kwh total life, assuming each 24 kwh yields 100 miles: = 100K miles

So old battery pack should last 3 times longer than new battery pack, IF the 3000 cycles mentioned earlier in the thread is true.