Does Nissan Really Recommend Only 80% Charging?

[FairwoodRed]

I’ve seen quite a few posters here state that Nissan recommends only charging to 80%. I can only assume that is based on the existence of the 80% Long Life Mode charging timer. It’s very name implies something other than standard life. If you want standard life, then go ahead and charge to 100%. Aren’t Nissan’s “80% capacity in 5 years” comments based on standard life? I agree that 80% charging is gentler on the battery, just like I agree that Synthetic Oil is gentler on an engine. But most car makers are not saying that regular oil will damage your engine (high performance engines excluded).

Now I don’t claim to have kept up with everything, so please point me to the proof. Where does Nissan say that that 100% charging will cause wear faster than standard life? Or has it been a case of exaggeration and spin?

 

[mwalsh]

"80% charging improves battery longevity". It says this twice in the Charging section of the User Manaul alone.

 

[ericsf]

Yes they do. 2 reasons:
1) Keeping the battery for long periods of time fully charged causes it to age faster than at 80 or even better 50%.
2) More smaller discharge cycles are better than big ones. i.e. two 40% cycles is easier on the batterty than one 80% cycle.

The following is a great wiki page where all the knowledge on what can cause the battery to age is being collected:
http://www.mynissanleaf.com/wiki/index.php?title=Battery_Capacity_Loss

On a side note, it's ironic and sad that this is one of the few things Nissan communicated to owners to help them maximize their battery life and it's used against them in the class action lawsuit on fact that the 100 miles range claim was misleading (YMMV, duh). So don't expect any other help on how to best take care of your car.

See : http://www.mynissanleaf.com/viewtopic.php?f=9&t=10147

 

[Nubo]

I’ve seen quite a few posters here state that Nissan recommends only charging to 80%. I can only assume that is based on the existence of the 80% Long Life Mode charging timer. It’s very name implies something other than standard life. If you want standard life, then go ahead and charge to 100%. Aren’t Nissan’s “80% capacity in 5 years” comments based on standard life? I agree that 80% charging is gentler on the battery, just like I agree that Synthetic Oil is gentler on an engine. But most car makers are not saying that regular oil will damage your engine (high performance engines excluded).

Now I don’t claim to have kept up with everything, so please point me to the proof. Where does Nissan say that that 100% charging will cause wear faster than standard life? Or has it been a case of exaggeration and spin?

Nissan has said a lot of things about battery life but nothing that an owner can actually use to make decisions with any predictivity. "Long-life mode" seems obviously advtantageous but there's not description of the degree to which it might be advantageous. Likewise with heat, useage, etc... A list of guidelines, but nothing about what to expect if you do or do not follow them.

It's all "On the one hand... On the other hand..."

 

[adric22]

Personally, I've never seen anything from Nissan that suggests you must use the long-life mode to keep your warranty. The only comparison I can think of from a business standpoint is Apple MacBooks (and possibly other laptops). In the energy saver section where the display sleep time is configured, if you set the display to "never sleep" it will come up with a warning that it will shorten the life of your display. Presumably they are talking about the backlight, I would imagine. Still, nothing that suggests it affects your warranty to do that.

 

[grommet]

Keeping this type of battery chemistry near 100% for long periods of time has been proven to be detrimental to the battery's lifespan, hence the recommendation. (Tesla Roadster owners have much experience here.)

If you charge to 100% every time, but generally use the energy quickly so the vehicle doesn't sit over 80% for extended periods of time, the impact of 100% charges should be far less significant over the lifetime of your battery. But this takes some effort on the owner, so using 80% mode by default when you don't really need 100% range is easier.

Heat and the Calendar are far bigger enemies.

 

[DaveinOlyWA]

take a round bowl, fill it with water to the brim. then take a walk around the block. see how much of that water is left.

then take the same bowl, fill it to 80% of its capacity. do the same thing.

now, this analogy is greatly simplified but the principle is the same.

degradation takes on many forms and one of them is overcharging. now what makes that worse is that a "full charge" is a moving target since its a chemical reaction so changing temperatures can cause that target to move in an unfavorable direction.

so, 80% charging simply allows that extra fudge factor to reduce that possibility.

the other factor to consider is the issues of extremes; fully charged or fully depleted.

take a flimsy cardboard box. fill it with large steel balls so if covers half the bottom. hold it steady, its fine. now start tipping the box side to side, what happens? the weight of the balls causes the box to shift in an increasingly uncomfortable way. your battery will do the same thing.

what you have is basically two items A and B. when your battery is half charged, A=B. when your battery is depleted, A>B and when your battery is fully charged, B>A.

so like any ratio that spends too much time being lopsided, a much stronger force is required to get the situation back to A=B. spend too much time at either extreme and you will lose the ability to convert.

now, the quantitative risk to any of this is very small in itself. but do it once/twice a day for a year. it adds up. now that quantitatively small risk is 365 times larger and then must be added to the cycling issues (iow, the chemicals do get tired)

so ya, its a "good" idea but then again, if you charge it fully and then drive off, it simply aint enough to worry over it.

after all; what you should be worried about is walking, being stranded on the side of the road, etc

 

[FairwoodRed]

"80% charging improves battery longevity". It says this twice in the Charging section of the User Manaul alone.

I don’t see that this says NOT to charge to 100%.

Yes they do. 2 reasons:
1) Keeping the battery for long periods of time fully charged causes it to age faster than at 80 or even better 50%.
2) More smaller discharge cycles are better than big ones. i.e. two 40% cycles is easier on the batterty than one 80% cycle.

On a side note, it's ironic and sad that this is one of the few things Nissan communicated to owners to help them maximize their battery life and it's used against them in the class action lawsuit on fact that the 100 miles range claim was misleading (YMMV, duh). So don't expect any other help on how to best take care of your car.

I get that lower SOC for longer times (and shallow cycles) will IMPROVE battery life, but I don’t see that 100%, just before leaving, will cause ABNORMAL wear.

So again, where does Nissan say not to charge to 100%? Or that charging to 100% will give less than standard life? Or even if Nissan said it was a Bad Thing (tm)?

 

[DaveinOlyWA]

charging to 100% does NOT cause abnormal wear however the likelihood of "additional" wear is greater at 100% than at 80% hence the recommendation.

once again, lets not read more into these statements than what is there. all statements are conditional and for an EV, the #1 conditional question you should be asking yourself is

"Can I make it or be comfortable making it on an 80% charge?"

use the answer to this question and this question alone to answer the question of the OP

 

[mwalsh]

I guess I'm less literal than you. I see an implication that 100% charging IS more detremental than 80% charging, whether it actually says that or not.

 

[gaswalla]

Personally, I've never seen anything from Nissan that suggests you must use the long-life mode to keep your warranty. The only comparison I can think of from a business standpoint is Apple MacBooks (and possibly other laptops). In the energy saver section where the display sleep time is configured, if you set the display to "never sleep" it will come up with a warning that it will shorten the life of your display. Presumably they are talking about the backlight, I would imagine. Still, nothing that suggests it affects your warranty to do that.

Since there is no warranty on the battery in regards to degradation or capacity losses - it doesn't seem the charging pattern would affect the warranty. On the other hand, since there is no warranty, it would appear that the owner would want to do everything possible to avoid capacity losses since they will suffer the losses alone - Nissan could care less.

 

[Stoaty]

There is lots of data in the Wiki (some for different Lithium ion chemistries) that strongly suggest that 100% charging is not going to be as good as 80% charging for battery life:

http://www.mynissanleaf.com/wiki/index.php?title=Battery_Capacity_Loss#Factors_Affecting_Battery_Capacity_Loss" onclick="window.open(this.href);return false;

It's a no-brainer to keep the average SOC as low as you can (down to about 30%) for as long as you can without overly inconveniencing yourself.

 

[planet4ever]

If you want standard life, then go ahead and charge to 100%. Aren’t Nissan’s “80% capacity in 5 years” comments based on standard life?

Since there is no warranty on the battery in regards to degradation or capacity losses - it doesn't seem the charging pattern would affect the warranty. On the other hand, since there is no warranty, it would appear that the owner would want to do everything possible to avoid capacity losses since they will suffer the losses alone - Nissan could care less.

It seems to me that gaswalla has stated the key point here, but I'd like focus it a bit on FairwoodRed's assumption. Here is Nissan's "80% capacity in 5 years" statement straight from the owners manual:

NISSAN estimates that battery capacity will be approximately 80% of original capacity after five years, although this is only an estimate, and this percentage may vary (and could be significantly lower) depending on individual vehicle and Li-ion battery usage.

So it is an estimate, not a warranty; it could be much lower, as our Phoenix friends are discovering; and it depends on how you use the battery, such as, perhaps, how much time it spends above an 80% charge.

Ray

 

[FairwoodRed]

I started this thread because several people have stated “Nissan said 100% is bad” and I hadn’t seen anything like that. I’ve read many of the opinions on battery care best practices and that wasn’t what I was asking about. Only what Nissan actually said.

So thanks to those who responded as I now think I have my answer. Nissan did not say that charging should be limited to 80% . Only that 80% will be better. Kind of like on a battery longevity scale that 60% rates at 10, 80% rates a 9.5, 100% rates a 9 (all degrees of good), but 0% rates a 1 (bad).

 

[mwalsh]

I started this thread because several people have stated “Nissan said 100% is bad” and I hadn’t seen anything like that. I’ve read many of the opinions on battery care best practices and that wasn’t what I was asking about. Only what Nissan actually said.

Except that really isn't what you asked. You asked where Nissan had said that charging to 100% would cause wear quicker than "standard life"(?). I gave my interpretation of that.

But still, so long as you're happy enough, I guess.

 

[FairwoodRed]

Fair enough. I am happy with the feedback I got.

 

[DanCar]

The guy at battery university.com says that li-ion batteries are over spec'ed on voltage to increase capacity. So if the voltage is lower, there is less damage going on, and therefore only charging to 50% or less means longer life. There is also a problem with too low of a voltage, but I don't know the details.

 

[DaveinOlyWA]

that issue is well known which is why cellphone batteries die so quickly. they are charged to give more "range" and therefore are overcharged. the LEAF pack even when charged to 100% is actually only charging to a level that is in the high 90's.

with that in mind; the main concern is still how long the pack remains at a high state of charge. now is there going to be a significant long term difference between driving off immediately after a 100 % charge is complete or is it ok to wait a few hours? and long can we wait on the extreme end before we see any significant damage?

this is info that even Nissan is unlikely to have since not sure that a rapid charge/discharge procedure does not allow this kind of info which is one of the reasons why i think its vital to allow Nissan to access what ever charging data they need.

i "hope" Carwings is not their only avenue and I have to assume that the required annual battery checks is their opportunity to download the info needed to analyze data for these types of questions

 

[DanCar]

>the LEAF pack even when charged to 100% is actually only charging to a level that is in the high 90's.
Interesting because the Chevy Volt is only charged to the 70 something % mark, if my memory is correct. Similar with prius plug in. Therefore those batteries will last longer.

>with that in mind; the main concern is still how long the pack remains at a high state of charge.
Yes, and temperature of course is also an issue. The hotter it is the more battery degradation occurs. I believe batteryUniversity.com says that significant degradation starts to occur around the 100 degree mark. Not something I have to worry about living in the bay area, but Phoenix where temps near the asphalt are 130 or more is a different story. http://www.pavements4life.com/QDs/Environment_1HeatIsland.asp

>now is there going to be a significant long term difference between driving off immediately after a 100 % charge is complete or is it ok to wait a few hours?
Yes, it would be good if Nissan gave us their data. Also if the leaf plotted this information for you (temperature, voltage, time) and spitted an estimated degradation value, that would be awesome.

>i "hope" Carwings is not their only avenue
They have done many tests on the battery so they already know.
They can confirm it with the Carwings data and have specifics for each car.

 

[scottf200]

>the LEAF pack even when charged to 100% is actually only charging to a level that is in the high 90's.

Interesting because the Chevy Volt is only charged to the 70 something % mark, if my memory is correct. Similar with prius plug in. Therefore those batteries will last longer.

The Volt's SOC range is generally from 22% to 87% so 65% used. It can dip into the teens. (LEAF has 21kWh usage out of 24kWh so ~87.5%)

I have seen one non-GM presentation from a battery company owner that indicated some of the 35% is used for "thermal management power requirements".