Has my battery capacity already dropped THIS much?

[turbo2ltr]

The BMS won't let you quick charge to "top off" it starts ramping down the charge rate by 80% SOC. That's also why regen is limited by the BMS when driving at a SOC > 80%.

Have you seen the charge profile for these batteries?

I get full regen way above 80%

Amount of energy that you can put into the batteries for a given SOC is dictated simply by what the maximum cell voltage rating is, it's not what your current SOC is.

 

[edatoakrun]

http://home.roadrunner.com/~mhebert/rm/Battery_Information_Sheet.pdf

First time I saw this, thanks. Seems to me to say that frequent charging from a high state of charge-'topping off' to 100%-does the most harm.

Seems to (somewhat) contradict the conventional wisdom of other battery life threads, that avoiding fast charging, especially to 'top off', was the best battery life extension technique. Or am I misremembering what I've read?

Lithium batteries don't like to be stored when close to 100% full. The longer they are stored at high SOC, the faster the battery degrades. Even worse is if this is done at high temperatures.

By frequently topping off the battery, you are making sure the battery spends more time at or near 100% full.

The BMS won't let you quick charge to "top off" it starts ramping down the charge rate by 80% SOC. That's also why regen is limited by the BMS when driving at a SOC > 80%.

Are you saying that charging from 80% to 100% (at the reduced rate as controlled by the BMS) has no (or little) effect on battery life, beyond that caused by the additional time spent by the battery at the higher rate of charge? Is this also true for DC charging from 80% to 100%?

If reduced battery life due to 100% charging is mostly or entirely a function of the amount of time the battery spends at between 80% and 100% of charge, wouldn't 'just in time" charging of that final 20% be a good idea?

I plan to 80% home charge, then 'top off' to 100% ONLY if I expect to need it. Is there significant benefit to waiting until just before I drive (rather than many hours or days earlier)to do this?

 

[LEAFfan]

Do you really believe that we will not have better storage devices in electric cars three years from now?

It isn't just about better batteries, but will there actually be a better and less expensive car by then? Nobody knows. It's a gamble. Remember, we don't even know if the $7500 tax credit/rebate (if it gets changed) will be there 3 years from now.

 

[GeekEV]

All this 80% and 100% stuff kills me. I am charging to 100% every night so I have full range every day. We'll see what happens. I'm not going to worry about it, I'm just going to drive the dang car.

 

[edatoakrun]

All this 80% and 100% stuff kills me. I am charging to 100% every night so I have full range every day. We'll see what happens. I'm not going to worry about it, I'm just going to drive the dang car.

Not having a LEAF yet, I have plenty of time to sit here and think about it...

Seriously, Nissan has studied these batteries for years, and for those of us who would like to make the battery last as long as possible, and don't need 100% charge, a little more info would be useful.

When I try to make an analogy about the possible benefits of 'long-life' 80% charging, I say it's a marginal benefit, like changing the oil in your ICEV every 6,000 miles, instead of the Mfrs recommendation of every 12,000 miles. Of course, I have no real info, and I'm only guessing...

 

[DarkStar]

You can't forget that even charging to 100% isn't really 100% of the actual battery. It just means that you're at 100% of the 24 kWh you have to use.

 

[SanDust]

Seems like charging to 80% is more designed to prevent constant topping off than anything else. IOW charging to 100% isn't a problem if you run down the SOC between charges, though if you look at the chart of issue running the SOC down too quickly can create problems as well.

I was surprised however that the Blink CS who called made a point of suggesting to only charge the battery to 80%. Obviously that's part of their script since the CS rep had to go out of his way to talk about it, which means Nissan is sufficiently concerned about it to want to make a point of it.

So is the recommendation to charge to 80% the result of issues unearthed during testing or does is simply represent an overabundance of caution? In either event, what does it say about the effective range of the Leaf? Doesn't this reduce the effective range by 20%?

Obviously if you planned to lease it's much less of an issue.

 

[thankyouOB]

Seems like charging to 80% is more designed to prevent constant topping off than anything else. IOW charging to 100% isn't a problem if you run down the SOC between charges, though if you look at the chart of issue running the SOC down too quickly can create problems as well.

I was surprised however that the Blink CS who called made a point of suggesting to only charge the battery to 80%. Obviously that's part of their script since the CS rep had to go out of his way to talk about it, which means Nissan is sufficiently concerned about it to want to make a point of it.

So is the recommendation to charge to 80% the result of issues unearthed during testing or does is simply represent an overabundance of caution? In either event, what does it say about the effective range of the Leaf? Doesn't this reduce the effective range by 20%?

Obviously if you planned to lease it's much less of an issue.

IOW?

 

[HIOJim]

IOW?

"In Other Words"

 

[JimK]

IOW?

"In Other Words"

Good thing, I thought it meant "Idiots on Wheels" :lol: :lol: :lol:

 

[evnow]

As one soon to get delivery, all these comments raise a question. If I have a three year lease and do not intend to keep the car, what is the downside to charging to 100% all of the time?

Can't regen much in the first few miles.

 

[Herm]

Seems like charging to 80% is more designed to prevent constant topping off than anything else

It does reduce the life of lithium-ion batteries to keep them at a 100% state of charge, this is a well known fact. These batteries should be topped off just before a long trip, but not kept in that state most of their life. Eventually better batteries will be made.

 

[tbleakne]

http://home.roadrunner.com/~mhebert/rm/Battery_Information_Sheet.pdf . . .
Seems to me to say that frequent charging from a high state of charge-'topping off' to 100%-does the most harm.

Seems to (somewhat) contradict the conventional wisdom of other battery life threads, that avoiding fast charging, especially to 'top off', was the best battery life extension technique. Or am I misremembering what I've read?

Lithium batteries don't like to be stored when close to 100% full. The longer they are stored at high SOC, the faster the battery degrades. Even worse is if this is done at high temperatures.

By frequently topping off the battery, you are making sure the battery spends more time at or near 100% full.

I would agree that one should not top-off the battery routinely and then store the car, but charging to 100% the night before a full-range outing is still prudent, because getting caught at the low end is worse. Many Leaf owners who are commuting to work simply do not have the luxury of limiting their charge to 80%.

My recollection concerning the long-running 80% vs 100% charge discussion is that a couple of months ago some folks on this forum were convinced that charging to 100% frequently was not a problem, despite what Nissan says. The discovery of 3 KWhr of hidden capacity at the top end seemed to add some credibility to this view.

There is no question that high SOC combined with elevated temperatures is a degradation factor for Li-Co batteries. Tesla warns about this on their web site. However, I have not been able to find any corresponding SOC warnings on Li-Mn batteries. We do know that Li-Mn is more thermally stable, and this is why the Leaf does not need active battery cooling.

From an earlier "thermal management" post:

. . . lithum-ion cells used under these conditions are about 99% efficient. Thus 1% of the stored energy will be converted to heat.

note that losses increase rapidly once you go past 80% soc.

If charging efficiency drops at the high end, this would help explain why L2 charging slows down at the top, and why QC stops at 80%. Non-linear stuff is going on in the top 20%. If stopping charge at 80% has X amount of benefit, this nonlinearity suggests that stopping at 90% should have > X/2 benefit.

 

[Essiemme]

I've been reading this post and I still wonder, could it be possible for some of the very first Leaf owners to notice any degradation in battery performance, I mean, degradation in its capacity ???

I'm sure they must have done a significant number of charge/discharge cycles...

 

[mwalsh]

I'm sure they must have done a significant number of charge/discharge cycles...

Not seeing anything noticeable yet, except for not getting full range from that first SOC bar. But it's been doing that since the first couple of weeks, and I can restore full range to that one bar with certain tricks (like preconditioning the passenger cabin before I unplug).

 

[DaveinOlyWA]

i think its way to early to make a positive statement on that. for one thing, the entire season you will encounter needs to be run first.

right now, we (according to KING 5 TV last night) are ending the coldest April in history. that would jive considering it was a miserable day yesterday with very heavy rains and temps were 37º on my way home

well, i "was" seeing a good 10 mile boost in freeway range when the temps were warmer earlier in the month. MPK reset on the energy screen were verifying averages running between 5.4 to 6.1 kpm.

but now with the cold, same essential driving and i am back to the Feb figures of 4.3-4.8 mpk

i cant wait to see what i can do when June and 70º hits this area

 

[LEAFfan]

I can restore full range to that one bar with certain tricks (like preconditioning the passenger cabin before I unplug).

How many minutes before unplugging do you precool? Could I just charge to 80% using Carwings (Blink will shut off), then later when I'm almost ready to leave (in 15 mins. or so) will the Blink come back on just for the pre-cooling?

 

[mwalsh]

I can restore full range to that one bar with certain tricks (like preconditioning the passenger cabin before I unplug).

How many minutes before unplugging do you precool?

I haven't been precooling yet. I've been preheating. And I've typically done 30 minutes of, on account of the relatively anemic heater (though I just a couple of days ago learned of the max temp trick to make the heater work harder, but won't get a chance to use it now until next winter).

 

[DaveinOlyWA]

30 mins is waaaay overkill. had to park 2006 Pri in garage one day for cleaning so had Leaf out over night. it ended up being around 20º. i did a preheat of just 8 minutes or so and it warmed up just fine. i judged the effectiveness by standing at kitchen window drinking coffee. as soon as the ice was gone off all the windows, i figured that was good enough

 

[mwalsh]

as soon as the ice was gone off all the windows

Huh? What is this "ice" of which you speak? :lol: