Charging from 80% to 100% -- What's the issue?

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gbarry42

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Joined
Jan 10, 2011
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Moonlight Beach
Nissan states that charging to 100% from 80% (or above) is not good for the battery. While I can think of things that may happen near a full charge, 80% doesn't sound to me like it's "that close" to a full charge. Especially if we figure there is a little extra hidden headroom to start with. I know special things happen near the end of charge, but the charge controller should certainly know when it's in that region and respond accordingly.

Can anyone figure out what Nissan is worried about here?
 
They're worried about people never taking it down below 80% and spending most of it's life at 80% charge or higher. Lithium batteries don't like to be stored when full.
 
I'd love to see a definitive white paper on these kind of issues from Nissan's research. But I imagine that would open a can of worms both from a competitive standpoint as well as liability and complaints from overly-concerned owners. Similar as when Mazda decided to put a fake "oil pressure gauge" in my last car which was really only a glorified "idiot light". Seems they were tired of answering questions and concerns about normal pressure variability between hot and cold engines, etc...

My opinion is treat the battery as gently as you can but don't sacrifice utility or even convenience unnecessarily.
 
I've got over 15,000 miles (58 miles per day avg.) and I've charged to 100% all the time. The dealer said my battery was in perfect condition at the 15k checkup the other day... :cool:
 
TangoKilo said:
I've got over 15,000 miles (58 miles per day avg.) and I've charged to 100% all the time. The dealer said my battery was in perfect condition at the 15k checkup the other day... :cool:

Do you have it timed so charging finishes shortly before you leave?

Although wasn't the question specifically about charging to 80%, and then later topping off to 100%? Although come to think of it, you can't charge to 100 without first charging to 80? Unless there is some concern about "pausing" the process at 80. I have done this a few times when I first thought I'd only need 80 then later decided I needed more range before I ever left and topped off to 100.
 
My understanding of the recommendation was that it's fine to charge from 80% to 100% but that you should take it down to 80% or lower before charging up all the way, at least routinely. Then the winter came along and the car is getting prewarmed daily, definitely charging over 80% after previously charged to 80%. It's not unusual for me to prewarm all the way to 100%. For me, the question is how bad is it to prewarm after 100% charging. everyone routinely charging to 100% then prewarming appears to be allowed to "overcharge" the battery. seeing that most folks in the EV project are charging to 100% daily and prewarming, it seems if this were a problem, it could become a big problem. My conclusion is that Nissan has provided us with some general rules of thumb but for the most part have engineered out any ways to truly abuse the battery. I'm not worrying much about it. I charge to 80% and prewarm/top off as much as I need and figure the battery spends little time hanging out at 100% or however much over "100%" we are allowed to charge using prewarming if already at 100%.

from what I've read, the real issue with true 100% charging li-ion batteries is that leaving the battery at a high state of charge for long periods can lead to cladding of the anode/cathode and reduce capacity over time and it's within the upper 20% of the true 100% of the batteries capacity where more of the energy is lost to heat, and the heat is also degrading to the battery. there has been a lot of discussion about whether we are truly able to get at the true 100% of the battery or not, I tend to think we don't or at least we tend not to leave the car at a high enough charge long enough for it to really be a big issue. If the studies of li-ion batteries and cycle life apply to the Leaf's particular battery chemistry, it does seem to be worthwhile to reduce the time the battery spends at very high or very low charge states. Fortunately, the battery management system of the car makes it easy minimize impact based on the users preferences and needs. I have adopted the assumption expressed in other threads that time is ultimately going to rob the battery of capacity regardless of how it's charged. Ultimately though, I figure I'm way more likely to replace the battery before significant degradation occurs because a cheaper, higher capacity version will likely come out soon enough. How I charge this one will probably be moot.
 
My understanding is that another reason to go for 80% (if it suits your needs), is that the last 20% of charge is less efficient. Does anyone have a ballpark estimate to quantify that effect?
 
Well, I belive we have a little built in headroom.

To the best of my knowledge, 4.2 volts per cell is considered maximm full charge for Li Ion.
From my observations and those of others, a LEAF 100% charge yields almost exactly 4.1 volts per cell.

Bill
 
TangoKilo said:
I've got over 15,000 miles (58 miles per day avg.) and I've charged to 100% all the time. The dealer said my battery was in perfect condition at the 15k checkup the other day... :cool:

There is nothing wrong with charging to 100% and driving away, I do that a lot. By the time you get 10 or 15 miles down the road it will be down a couple of bars anyhow.

The only thing I would avoid is charging the car to 100% and then going on vacation for a month, now that would not be a good thing to do.

KJD
 
agreed, +1

KJD said:
TangoKilo said:
I've got over 15,000 miles (58 miles per day avg.) and I've charged to 100% all the time. The dealer said my battery was in perfect condition at the 15k checkup the other day... :cool:

There is nothing wrong with charging to 100% and driving away, I do that a lot. By the time you get 10 or 15 miles down the road it will be down a couple of bars anyhow.

The only thing I would avoid is charging the car to 100% and then going on vacation for a month, now that would not be a good thing to do.

KJD
 
Nubo said:
My understanding is that another reason to go for 80% (if it suits your needs), is that the last 20% of charge is less efficient. Does anyone have a ballpark estimate to quantify that effect?
I looked through my notes, and charging from 8 to 10 bars (as well as calculating two bars by doing arithmetic on longer charge runs) comes out to 30 - 45 minutes to charge 2 bars. When I do the same thing to go from 10 to 12 bars, it takes about 90 minutes.
 
The power drops as you approach 100%.

I've been monitoring the charging times and the charging power, and from observation I've watched the power drop from the maximum power of 3.7Kw (~240V 16A) to below 3Kw as it nears the end.

It's quite obvious that the charging is done carefully when you're nearing 100%. Maybe it's that cell balancing thing I'm always hearing about...

gbarry42 said:
Nubo said:
My understanding is that another reason to go for 80% (if it suits your needs), is that the last 20% of charge is less efficient. Does anyone have a ballpark estimate to quantify that effect?
I looked through my notes, and charging from 8 to 10 bars (as well as calculating two bars by doing arithmetic on longer charge runs) comes out to 30 - 45 minutes to charge 2 bars. When I do the same thing to go from 10 to 12 bars, it takes about 90 minutes.
 
LTLFTcomposite said:
TangoKilo said:
I've got over 15,000 miles (58 miles per day avg.) and I've charged to 100% all the time. The dealer said my battery was in perfect condition at the 15k checkup the other day... :cool:

Do you have it timed so charging finishes shortly before you leave?

Although wasn't the question specifically about charging to 80%, and then later topping off to 100%? Although come to think of it, you can't charge to 100 without first charging to 80? Unless there is some concern about "pausing" the process at 80. I have done this a few times when I first thought I'd only need 80 then later decided I needed more range before I ever left and topped off to 100.

I don't use the timers. I plug in whenever, wherever...
 
jfreire said:
The power drops as you approach 100%.

I've been monitoring the charging times and the charging power, and from observation I've watched the power drop from the maximum power of 3.7Kw (~240V 16A) to below 3Kw as it nears the end.

It's quite obvious that the charging is done carefully when you're nearing 100%. Maybe it's that cell balancing thing I'm always hearing
That is the way Li cells are charged.

The charge starts at constant current (16 Amps for L2) and stays at that current until cell voltage reaches 4.1 volts.

Then the voltage is held constant and current decreases to some design percentage of 16 Amps. Maybe 10% (1.6 Amps)? I don't know, but I believe 10% is rather common.

Bill
 
The main reason I charge to 80 percent is that I have about a 1,000 foot descent from my house and I much prefer having regen available for that descent. The difference in range between 80 and 100 percent is small for me because of that...
 
I have yet to see the Leaf ever "fully" charge according to it's SOC number, now I haven't looked every time, just occasionally. My last charge where I checked was from about 45% SOC and it completed on it's own at 94.591% SOC. The stored capacity was reading 22.240kWh.

I always charge to 100% as well and have zero loss of capacity after almost 200 charge cycles.

-Phil
 
Phil, where do you read the SOC % value and the stored capacity ? Does the car provide that data in the Nav windows, or do you get that using your own device which you had designed and installed in your car ?

thanks
Jay
 
Reading through the posts in this topic, do I conclude there is no clear consensus that charging full to 100% all the time does some harm or no harm from the perspective of long term health and capacity of the battery ?

I am planning to only charge through L1 at my home for the foreseeable future. Would that make any difference ? I am planning to not plug in until it comes down less than 50%, and then charge fully to 100%. That might mean charging every day or skipping a day or two depending on how much I end up driving that day.

thanks
Jay
 
Ingineer said:
I have yet to see the Leaf ever "fully" charge according to it's SOC number, now I haven't looked every time, just occasionally. My last charge where I checked was from about 45% SOC and it completed on it's own at 94.591% SOC. The stored capacity was reading 22.240kWh.
I always charge to 100% as well and have zero loss of capacity after almost 200 charge cycles.
-Phil

On L2, I did hit 100%SOC one time. I have no idea how it happened, but it was a big surprise because all the other times it's always between 94-95%SOC. With QCing, the highest I've gotten is 93.5%SOC and that's after the additional 30 minutes beyond the 20-30mins. to 80%.
 
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