Limiting the Charge to 80%

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jdharrin

Member
Joined
Apr 22, 2014
Messages
5
Hi everyone, Just bought the wife a new Leaf. While she's the primary driver, I'm trying to help her understand the car and its systems. She's the typical "gas it and go" type, so there's a steep learning curve for her.

My first question is, is their a way to set the charging limit to 80%, either with the car or the charger itself so that it stops charging once it's reached that level? My dealer said we ought to do this unless we're planning a long trip, but I can't find anything to set percentage limits short of doing it myself (I found the timers but I still have to manually calculate when to turn off). If I need to calculate and control this myself, then the next question is, does the Leaf charge linearly (i.e. the first hour's charge is no more or no less than every other hour's charge).

Does this math make sense?

-- 100% charge: batteries hold 24 kWh; Charger supplies 6.6 kW (on a 240v charger), three hours, 40 minutes to full 100% charge.

-- 80% charge: batteries charge to 19.2 kWh; Charger supplies 6.6 kW (on a 240v charger), two hours, 55 minutes to 80%.

I'm probably making this way more difficult than necessary. Any help would be appreciated...

J.D.
 
Nope! In order to game the EPA range numbers, Nissan eliminated 80% charging in 2014... You could use a timer to stop charging at the appropriate time but that is hit and miss at best...
A much better solution would have been the way that Tesla does it!


jdharrin said:
My first question is, is their a way to set the charging limit to 80%, either with the car or the charger itself so that it stops charging once it's reached that level?
 
Appreciate the quick reply. You said, "Nissan eliminated 80% charging in 2014..." Is that available somewhere on their website where I can confirm it? I know that Nissan dealers have problems keeping up with all the issues involving their cars, so maybe they haven't heard it yet. It would surely help my wife if that's the case. We just bought a 2014 and it would be one less thing to worry about... :D

J.D.
 
There is no empirical evidence that suggests that charging only to 80% helps you Leaf battery anymore more than charging to 100% every time. Anecdotally degradation has been just the same for anyone charging full everyday to someone babying their car. What might help though is to limit the time your battery stays at 100% to as little as you can using the timer.

Remember a full charge in a Leaf is only upto 21 kWh though the capacity s 24 kWh. So 100% is not really 100%.
 
mkjayakumar said:
...Remember a full charge in a Leaf is only upto 21 kWh though the capacity s 24 kWh. So 100% is not really 100%.
That's not strictly true. A "100%" charge is about 94-95% actual SOC, or about 22.5 to 22.8 kWh. But there is also some charge at the bottom (~2% IIRC) that is not used before the car shuts down. The reason we use 21 kWh as a rough measure of usable charge on a new LEAF is partly because of that top limit and bottom limit, but also because few want to get to turtle or shutdown on a regular basis. Just sayin'...
 
Set the departure time and drive. Just do not park it at 100% for an extended period. If she needs more range use the timer override for immediate charge.
 
jdharrin said:
Appreciate the quick reply. You said, "Nissan eliminated 80% charging in 2014..." Is that available somewhere on their website where I can confirm it? I know that Nissan dealers have problems keeping up with all the issues involving their cars, so maybe they haven't heard it yet. It would surely help my wife if that's the case. We just bought a 2014 and it would be one less thing to worry about... :D

J.D.

Google around about differences between the 2013 LEAF and 2014 LEAF. It's disappointing that your Nissan dealer advised you to charge to 80% since 2014 LEAFs don't have that option. Here's the story behind that change.

Starting with the 2011 model Nissan provided a "long life mode" which allowed the user to set a charge timer to stop at 80%. In the 2011 and 2012 LEAFs some owners (and I am one) configured the timer to always charged to just 80% - we have to hit the "timer-off" button or enable "charging now" via the LEAF app if we want it to charge to 100%.

In the 2013 model Nissan implemented an 80% charge switch for the S model since there was no navigation screen with which to set the 80% charge timer.

Coincidentally, in 2013 the EPA tested the range of the LEAF and announced it was 75 miles. For the 2011-12 model years the EPA range was 73 miles, but some software changes to how the battery was used improved the LEAF performance on the EPA range test. However - and this is key to the story - the EPA also decided that since the LEAF had a 80% range mode that they would average the range at 100% charge (84 miles) with the 80% charge (66 miles) to get 75. Needless to say, they were widely panned for this but it stuck.

In the 2014 model Nissan quietly eliminated long-life mode from the navigation screen and the buttons. It no longer is mentioned in the 2014 LEAF manuals. However, there was no announcement about this. I asked a LEAF dealer who has been an expert on LEAFs since they first shipped and she told me that Nissan hasn't given dealers a reason for making the change.

So, we all are sure that at least part - if not all - of Nissan's motivation in making the change was to get the official EPA range up to 84 miles. But what we aren't sure about is what this means about the value of using "long life mode" (i.e. 80% charging) on older LEAFs. Based on data that has been shared on this forum, plus a few studies done elsewhere, it appears that regular charging to 80% has minimal effect on extending battery life. It probably has *some* effect, but it is probably tiny relative to the main causes of battery degradation, which are in order: 1) time the battery spends at high temperatures - approximately at temps of 80F or higher, with the negative effect growing exponentially as the temp rises, and 2 (tie)) miles driven and age of battery. There is some data which suggests that if your LEAF is going to sit at high temps it is better not to have it be charged to 100% - so the 80% charging suggestion may have some benefit in that situation.

Based on this data I'm not sure what to recommend for 2014 LEAF drivers. As you point out it is possible to charge to approximately 80% or thereabouts using a timed charging - but that can be a very fussy business if you don't have very regular driving habits. One downside to the timed charging is that sometimes you make a mistake and the car doesn't charge at all. I'd probably regularly charge to 100% if I had a 2014 LEAF except when I knew the car was going to sit for a long time without driving - especially if it was going to sit in the heat.
 
Outstanding input. I truly appreciate you taking the time to provide this background. Since my wife drives everyday, I'll tell her to plan to charge to 100%; that we should plan to garage the vehicle when at home since we live in Virginia with dozens of 90 plus temperature days during the summer; and when parked away from home, to try and park under shade trees with the windows cracked.

J.D.
 
The battery pack is under the car and is sealed so there is no good evidence that keeping the interior of the car cooler has any significant affect on pack temperature. Heat radiated under and around the car and the ambient air temperature has much more affect. Even then, the pack has a lot of thermal mass so it changes temperature (up OR down) slowly.

jdharrin said:
when parked away from home, to try and park under shade trees with the windows cracked.
 
Presumably the 2014 LEAF will now allow ONE single QC session to fully
(although somewhat slowly) charge the car (to 100% fullness).

This will allow the 2014 to get full for $5 instead of $10 on the QC
machines that charge $5 per session, and will tend to make
many charging sessions have a longer duration, increasing
wait times at many QC stations, right?
 
garygid said:
Presumably the 2014 LEAF will now allow ONE single QC session to fully
(although somewhat slowly) charge the car (to 100% fullness).

This will allow the 2014 to get full for $5 instead of $10 on the QC
machines that charge $5 per session, and will tend to make
many charging sessions have a longer duration, increasing
wait times at many QC stations, right?
The 2013 LEAF already lets you do that, Gary.
 
No need for EVSEs with timers and the like.

It is a bit of a kludgy workaround, but 2014 owners who don't need to charge to 100% every day might want to just set an end time for an hour or so after they plan to leave. They won't end up with the same amount of charge each day but it shouldn't matter much if range is not limiting.

Those SV/SL owners who only need a bit of charge each day can just use start and end timers to charge for an hour or forty-five minutes, or whatever amount is needed, to boost the charge back up. I do this most days so that I can keep the charge in the lower half of the battery range, unless I need to take a long trip. But I realize this is too much trouble for the "just get in and drive" crowd, rather, it is for those who enjoy fussing with the car as I do.

FWIW
 
An EVSE with timer would be useful here.

I assume on the 2014 Leaf you can set the departure time? If so, set the departure time on the Leaf to 7am (for example) and set the cutoff time on the EVSE to 5.45am. You will roughly end up with 80% charge.
 
As others have said, I wouldn't worry about the 80% thing because it turned out to be a waste of time for the most part. They only reason I still do it is habit and the fact that I do sometimes leave the car sitting for a few days at a time. With that in mind if you plan to leave the car sitting for a week or more, especially in high temperatures, you might want to drive the battery down to between 3-9 bars. Other than that, just use the car normally and charge it whenever you want--you will enjoy it a lot better. :D

jdharrin said:
Does this math make sense?
-- 100% charge: batteries hold 24 kWh; Charger supplies 6.6 kW (on a 240v charger), three hours, 40 minutes to full 100% charge.
-- 80% charge: batteries charge to 19.2 kWh; Charger supplies 6.6 kW (on a 240v charger), two hours, 55 minutes to 80%.

Actually the math is logical but it doesn't work out that way. Charging times and current rates are non-linear. On L2 and L3 charging it takes roughly as much time to go from 20% to 80% as it does from 80% to 100%. That last 20% is shoved in at reduced current because all batteries become increasingly difficult to charge the fuller they get. Therefore if time is most important than stopping at 80% is a more efficient use of the charger.
 
Plus, the charger outputs only 6.0Kw, you don't get the full 24Kwh of the battery to use, and there are parasitic losses from charging due to the cooling pump, charger inefficiencies, and the like.

SierraQ said:
Actually the math is logical but it doesn't work out that way. Charging times and current rates are non-linear. On L2 and L3 charging it takes roughly as much time to go from 20% to 80% as it does from 80% to 100%. That last 20% is shoved in at reduced current because all batteries become increasingly difficult to charge the fuller they get.
 
After doing 80 for 7 months and charging to 100 for the last 3 I am starting to think it actually increased degradation. Partially due to increased battery cycles the other part I am not certain
 
I have but two anecdotal data points, but here it is. I have religiously babied the battery and only charged to 80% most days, except when a long trip is planned, in which case I make sure to start the drive within a couple hours of completing the charge. I have a friend who lives in the same area, who has had his car 6 months longer and has driven 7000 more miles. He charges to 100% always. He has not lost a capacity bar, and I just lost one last month. So, yes, basically a lot of fiddling for nothing.
 
leafedbehind said:
I have but two anecdotal data points, but here it is. I have religiously babied the battery and only charged to 80% most days, except when a long trip is planned, in which case I make sure to start the drive within a couple hours of completing the charge. I have a friend who lives in the same area, who has had his car 6 months longer and has driven 7000 more miles. He charges to 100% always. He has not lost a capacity bar, and I just lost one last month. So, yes, basically a lot of fiddling for nothing.

I'd be interested to know the relative locations of home and work for you and your friend. No - I'm not looking for exact info and not stalking either of you. However, as you know there are big differences in micro-climates in the bay area. South San Jose is on average a lot hotter over a year than Daly City, for example. Wondering if your car was kept in locations that were on average hotter than your friends.

And yes, this matches my experiences too. We're still charging our LEAFs to 80% by default, 100% when needed, but I am increasingly wondering why.
 
DougWantsALeaf said:
After doing 80 for 7 months and charging to 100 for the last 3 I am starting to think it actually increased degradation. Partially due to increased battery cycles the other part I am not certain

Well, keep in mind the 7 months you did 80% the average temps were much hotter than the last 3 - which were cooler than the recent normal for the US. Based on data known to date the heat was the most likely cause of the difference.

Studies we've seen of similar, but not identical, battery chemistries have suggested that more frequent shallow cycles are better for battery longevity than fewer deep cycles. This is not conclusive for the LEAF battery but it's worth noting because if the LEAF battery were the reverse that would be surprising.
 
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