maintaining a low SOC to preserve battery life

[JeremyW]

With recent capacity bar losers in more temperate climates, there's some talk that keeping the charge closer to the middle of the pack is better then charging to 80%. If you have a short commute or otherwise don't need the range, try to stop charge around bar 6, and don't go below the lowest two bars.

Obviously, if you need the range, use the bars. However try to avoid high temps and high state of charge if at all possible.

Welcome to the 50% club.

I want to see what it takes to keep these packs alive without a TMS. Even with, I suspect it involves using a smaller percentage of the pack. Of course, I'm also waiting for the harp music from Nissan.

A "colorization" for the charge bars is:

[Thanks to gbarry42 for the visual]

You want to stay in the green as much is possible. Yellow is ok for short periods of time. Red is best to avoid. Yes this is pretty aggressive, but that's why this is an exclusive club. :lol:

I've ordered a sample lighting gel pack to make a transparency for the gauge face. Should be in on Thursday or Friday.

 

[Stoaty]

With recent capacity bar losers in more temperate climates, I think even 80% is not low enough for "long life mode."

I am trying to stay below 50% SOC unless I need the range. I suggest those that have very short commutes (or none at all) to do the same. I typically charge back to five or six bars after going to LBW or VLBW, and with my commute that takes a few days.

While I agree with your general approach (and do the same), I think a wiser way to implement this strategy is to keep the battery from going below 2 full bars. Charles Whalen was quoted in another thread (can't find it now) as saying that lower average SOC is better for the battery down to about 30% SOC (approximately 2 bars when car is new). The Volt allows SOC to only go down to around 23%. Shallower depth of discharge is likely to be better for the battery (based on studies of other battery chemistries). So in your case I would recommend charging to 4-5 bars, letting battery go down to 2 bars, then charging back to 4-5 bars.

 

[TonyWilliams]

How are you going to handle the número uno issue is heat? Sacto gets HOT!!!!

 

[GaslessInSeattle]

I've been in the "50% club" for a while now. I'm pretty convinced that low SOC is best for the battery at any temperature. I have no idea how much of a difference it will make though, we are going pretty blind at this point. I've decided to try and cycle between 3 and 8 bars, landing on 5 for overnight even if it means QC'ing on occasion (with a "hidden bar" at the bottom, 50% is more like 5 bars). I think the SOC meter should have red at the top two and bottom two bars then fading to yellow with green in the middle to help people get used to the concept of favoring the middle of the pack.

 

[JeremyW]

Stoaty, good advice and will try to stay above 2 bars, but I'm going to use them if I need to.

Tony, I do try to vent my garage out and move some air under my car with some cheap fans I got from goodwill. Yeah I know it's a pittance compared to mother nature.

Jeremy

 

[Stoaty]

Stoaty, good advice and will try to stay above 2 bars, but I'm going to use them if I need to.

Of course. However, if you charge nightly back to 4-5 bars instead of waiting a few days you should be able to do shallower cycling of the pack most of the time. No reason to let the battery get lower than 2 bars. If you think you are going to need more for a particular day, I believe it would be better to charge up to 6-7 bars for that morning rather than getting below 2 full bars at the end of the day.

 

[DaveinOlyWA]

Jeremy; you need to stay in the middle of the pack. i used to manually charge my LEAF to stay pretty much at the 30-70% SOC. this gave me around a 35-40 mile range but i was only doing a 13 mile RT commute and adding maybe 10 miles for side trips 80% of the times.

for the other 20%, my only rule was to start charge as late as possible the night before so the car sat no more than 3-4 hours at 100% SOC.

 

[GaslessInSeattle]

...for the other 20%, my only rule was to start charge as late as possible the night before so the car sat no more than 3-4 hours at 100% SOC.

same here. I don't hesitate to charge to 100% or QC as needed, I just avoid the high SOC when I don't need it.

 

[HairyCairy]

Thank you for this post. I completely agree. I am not sure if there is anyone or anywhere in this Owners Forum where we could make this thought a reality for the future generations of leaf owners and current.
I was trying to explain this to my better half, Mrs Hairy, and looks like I will have to try again after reading this topic.

 

[TomT]

And then we will wind up with people thinking they can only use 25-30 miles of the pack and suffering from real range anxiety! Other than not charging to 100 percent except when I must for my daily drive, I refuse to worry about it now (thank you Mr. Lease)! However, it (and TMS) will be a big consideration in my next EV which I expect to buy rather than lease!

I think the SOC meter should have red at the top two and bottom two bars then fading to yellow with green in the middle to help people get used to the concept of favoring the middle of the pack.

 

[garygid]

I believe that we have no evidence to support the idea that keeping the
LEAF's battery below 5 or 6 bars is any better than keeping it below
the 8 to 9 bars level.

However, keeping the battery cooler seems to reduce the aging effect.

 

[TomT]

+1!

I believe that we have no evidence to support the idea that keeping the
LEAF's battery below 5 or 6 bars is any better than keeping it below
the 8 to 9 bars level.

However, keeping the battery cooler seems to reduce the aging effect.

 

[Stoaty]

I believe that we have no evidence to support the idea that keeping the
LEAF's battery below 5 or 6 bars is any better than keeping it below
the 8 to 9 bars level.

However, there is evidence for another Lithium battery chemistry that this is the case:

http://www.mynissanleaf.com/viewtopic.php?f=30&t=8802&p=214785&hilit=lower+SOC#p214785" onclick="window.open(this.href);return false;

Charles Whalen, who appears to be quite knowledgeable has posted that lower SOC down to about 30% is beneficial (middle of page on this link):

http://gm-volt.com/forum/showthread.php?5243-Volt-thermal-management-system-temperature-band/page3&highlight=whalen" onclick="window.open(this.href);return false;

Suggests to me that it is still worth doing.

 

[JeremyW]

Updated with a new first post and suggested "color" bars.

I believe that we have no evidence to support the idea that keeping the
LEAF's battery below 5 or 6 bars is any better than keeping it below
the 8 to 9 bars level.

I'm doing this to give you some real world evidence that it does make a difference.

Jeremy

 

[garygid]

J,
Great experiment, thanks.

Have you had a chance to press the big red button yet?
Cheers, hope you are doing well, and getting settled.

 

[TomT]

Well then, how about we only use the range of 20 to 40 percent and drive less than 15 miles a day... That'll sure help EV adoption! :lol:

Charles Whalen, who appears to be quite knowledgeable has posted that lower SOC down to about 30% is beneficial (middle of page on this link)

 

[mark1313]

This thread would not help in the sales of the Leaf ..
I bought this car to save on gas from my long drives to work and back,the 2 bar rule would never work with me..
I would imagine anyone looking to buy a Leaf, but coming here first to read about the car and finding the battery capacity problems would probably stay away from it..

I do agree with the 2 bar rule,it makes a lot of sence to me..I just wish Nissan would of of done a more complete study of the car before they released it,then we would not of had the battery capacity problems that we are seeing ...
The 2 bar rule might have also cut sales in half tho..I would of stayed away from the Leaf because of my long drives..
I sometimes wonder if Nissan knew there may-be some problems in a few years with the batteries, but produced it anyways to learn from the problems..We being the mice behind the wheel

 

[DaveinOlyWA]

I believe that we have no evidence to support the idea that keeping the
LEAF's battery below 5 or 6 bars is any better than keeping it below
the 8 to 9 bars level.

However, keeping the battery cooler seems to reduce the aging effect.

i think there is a HUGE amount of evidence that minimizing the SOC swing does preserve longevity and i think that applies to nearly all types of battery chemistry with the exception of lead.

problem is weight/performance trade off. we run more of the charge profile to get more distance between charges but you probably would get the most distance by running SOC between 40-60% but that might wear out the charging port before the pack! so it would be logical to see a cycle/degradation curve that would be pretty flat out at the middle SOC range but even a ½% difference could be significant if applied over 10,000 partial cycles running 40-60% or 5,000 partial cycles running 30-70%

so we chose to ignore that very small difference because it is really insignificant. but that difference grows and the cycles get deeper. Nissan has arbitrarily chosen 80% and it is ok to say "hey! 80% is not in my BEST INTEREST"

another thing to keep in mind; is that Nissan's method minimizes concern on depth of discharge or have they? what apparently happened is Nissan took data from us (first users) and decided to adjust the bars on the GOM based on our driving/charging habits and why did they do that? most would say just to F with us...

my thoughts? they realized that maybe a lower setting would be convenient than 80% like maybe 65% but thought it too confusing to change that parameter so they changed the "unwritten" parameter so they buried more of the bars. did not change how the car operated one iota. so what did it change??

it change the driver's perception of when he should plug in again. so it reduced the SOC swing. before people might be comfortable running down to 15% SOC but after the change, now its more like 25% SOC.

 

[DaveEV]

i think there is a HUGE amount of evidence that minimizing the SOC swing does preserve longevity and i think that applies to nearly all types of battery chemistry with the exception of lead.

Even lead benefits from partial discharges - the difference between lead and Lithium/NiMH is that it likes to be kept full and discharged as little as possible where the others prefer to be kept in the middle of their SOC range.

 

[starry]

My situation is a bit complicated by the fact that my town in Orange County, CA is a bit isolated--some towns north of me, but nothing south of me for 20 miles. And my only path of convenient egress is Interstate 5. So I have to travel at highway speed (65mph+) to avoid getting run over by almost every other vehicle on the road. And that is in the slow lane!
When I have to travel to a friend's house about 17 actual miles away, mostly it is by freeway. That means I can get there if I charge to 80%, don't drive anywhere in the visit, and drive home, I get down to the 2 red bars or 23% of SOC on the GID meter on my car's CanBus.
When I travel to another friend's house that is 34 actual miles away, mostly it is by freeways. That means that if I charge to less than 100% the night before, hook up to his house at Level 1 (110vAC) when I arrive, drive a short distance to lunch, continue charging (a total of 6 hours there), I can just make it home with no red bars left, low battery warning and 3-5% of SOC on the GID meter.
After 16 months and 9400 miles on the car, I have noticed a decrease in maximum charge capacity. After replacing a battery module twice, and another one once, and a charging controller this past week, I can get 94% charge overnight. These repairs were initiated by a notice by the car to Nissan North America and a message by way of the dealership to me for need for service on the power system.
While Nissan has not mentioned the cause of these needed replacements, and has done them under warranty (total about $7500 to them so far), I think I have a reason for them. The first night I had the car, I charged it at Level 1 and it made a bubbling noise. The car was moved by wrecker to a dealership where they said an air bubble in the liquid system for the charger or battery cooling caused it. The next day I tried again at Level 1 and more bubbles. I measured the overflow tank temp to be 210*F before I cut off charging. The car was sent to another dealership for a week where a relay or switch for a heater circuit in the power system was replaced. The car has not bubbled since, but I am not sure about what other damage could have been done to the power system (battery or controller) because of that problem. Neither Nissan nor the dealer technicians have remarked on this.
I have not tried to go 60 miles down I-5 to my cousin's house yet. I would have to brave the freeway at 55-60mph max to make it. He says there are Level 2 charging stations nearby, so I could go down for the day, charge at Level 2 for 8 hours, and then make it 2/3 of the way back. I would get a charge at Level 2 for an hour or two in order to make it the last 20 miles to home.
Gregg
Stanleaf Steamer #1597, bought 3/28/11