Limiting the Charge to 80%

[LeftieBiker]

What's needed here is for the car to use its battery pack temp to allow or postpone charging, as needed. This would have to have an override button, but that isn't a big deal either...

 

[DaveEV]

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.

Well, if you want to talk anecdotes, I also have a friend who also charges to 100%, keeps the car in a cooler area, has fewer miles, and has a lower Ah reading than I do.

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.

There are some things that are certain about lithium batteries and that is:
1. Hotter is always worse.
2. Higher SOC is always worse (as long as you don't go too low).

It's just basic chemistry and physics. The question is how much worse the higher SOC is for the battery, but most anecdotal evidence seems to say that it's difficult to measure out in the real world, but I'm certain that in a lab test if you cycle one battery from 95%-55% and the other from 80%-40% the battery that is cycled from 80-40% will last longer.

 

[BrockWI]

I have been wondering abut this and the thing that comes to mind for me is if it is cooler (pack temps below 50F range) and charged to 100 right before we leave why not? My wife's job is unpredictable as to how much she drives every day, most days she has been running about 80% to 30%. But about once a week she has to run more and is running 80% to 10% (once so far) but a couple of times to 20%. Not that we can know when this happens but are we better off running from 100% to 30% or 80% to 10%?

Right now she can run home for lunch and we have winter off peak rates from noon to 4p and she can charge add 15% in 45 minutes, but as of May 1st we loose the noon-4p cheap rate.

 

[cgaydos]

Not that we can know when this happens but are we better off running from 100% to 30% or 80% to 10%?

I don't think we have sufficient data to know. We do know that there is more stress on the battery at either extreme - fully charged or near empty. But as noted above it doesn't appear to make a significant difference long-term versus the big battery degradation factors.

So we choose to do 100% in that situation simply because it gives us more flexibility during the trip. It also means that the car returns with more charge, so it is available for the next trip sooner. Since our anachronistic electric utility doesn't have time-of-day rates, we have no incentive to delay charging the car until the rates are cheaper.

 

[theds]

I live on top of a hill and I'd like to leave some room for regen charging going down hill. I couldn't figure out a way to stop charging at 80% or 90% on my 2014 SV. Nissan really should add this option.

 

[cwerdna]

I live on top of a hill and I'd like to leave some room for regen charging going down hill. I couldn't figure out a way to stop charging at 80% or 90% on my 2014 SV. Nissan really should add this option.

Yeah. There were previously choices for 80 and 100% (easiest on the '13) and during the whole Phoenix battery degradation debacle (and likely numerous other times), people have asked Nissan for more charge % choices. Andy Palmer and the other Nissan guy at the Phoenix meeting heard the request...

Instead, they removed it on the '14 :roll:, for reasons already discussed earlier.

 

[gbarry42]

Our plug-in gauges can tell us when we've reached 80%. So we should start thinking about a way to tell the car or the EVSE to terminate the charge session. We could select any charge level we like, actually. A beeper that sounds when we get there would be a start, I suppose.

 

[BrockWI]

Hey I hadn't thought about that. Can the can bus command the charge start stop?

 

[ERG4ALL]

We just traded in our 2011 for a 2014 and were faced with the same change in charging levels. My two cents is that, as has been mentioned, charging to "100%" will not do as much damage to the battery as letting it sit at 100% charge for extended periods. The reason I say that is twofold.

First, Nissan backed into a buzz saw with the heat issue in hot climates. As a result, they announced a more heat tolerant battery was to be released this April. Then, they created another layer of warranty that would replace the battery if it lost more than 25% of its capacity before 60.000 miles. I can't imagine that they would ask for another problem by eliminating the 80% charge if it were deleterious to the battery.

Second, because I'm more tech savvy than the average LEAF driver, the dealership has allowed me to speak on several occasions directly with the LEAF tech that is supposed to be one of the best. He indicated that the charging regulator on the car has been improved. The problem was that as the car approached 100% charge, it was heating the battery which could be a problem in some climates. The new version charges that last percent or two at a much slower (and perhaps modified amperage) rate, which gives the battery time to dissipate the heat. I've noticed this for a fact that the 2014 will charge much quicker than the 2011 due to the 6.6kW charger than the old 3.3kW charger FOR THE LOWER PART OF THE CHARGE. However, the old one seemed to apply that last bit of charge much faster than the new charger. Several times I have gotten into the new LEAF while the wall unit indicates the car is still charging. And yet, the dash displays that the car is charged to 100%. Our Aerovironment charger blinks, indicating that the charge is being applied intermittently, when it is adding the last bit of charge.

Anyway, we have another three year lease, so we will find out if the new battery lasts as long as the old battery. With "babying" the 2011, we did not lose our first bar of capacity until just over 30,000 miles. Time will tell.

 

[mkjayakumar]

I agree with the previous post. The degradation attributed charging to 100% is over blown. What might be a good thing is to not keep it at 100% for long periods. I exchanged some emails with a Nissan leaf test engineer at Phoenix who is also a member of this forum. And he emphatically says, charge it to 100% and use it without any concern.

 

[DaveEV]

The problem was that as the car approached 100% charge, it was heating the battery which could be a problem in some climates. The new version charges that last percent or two at a much slower (and perhaps modified amperage) rate, which gives the battery time to dissipate the heat. I've noticed this for a fact that the 2014 will charge much quicker than the 2011 due to the 6.6kW charger than the old 3.3kW charger FOR THE LOWER PART OF THE CHARGE. However, the old one seemed to apply that last bit of charge much faster than the new charger. Several times I have gotten into the new LEAF while the wall unit indicates the car is still charging. And yet, the dash displays that the car is charged to 100%. Our Aerovironment charger blinks, indicating that the charge is being applied intermittently, when it is adding the last bit of charge.

Unfortunately, most of that simply isn't true.

The only reason the '11-12 appears to charge the last bit faster is because it simply stops charging sooner.

The '13+ will spend a lot more time trickling in a bit of energy and balancing the pack than earlier LEAFs.

If anything, the '13+ charges the battery to higher overall voltages (you can see this as most '13+ LEAFs will charge to 96-97% SOC where older LEAFs commonly only charge to 93-95%, it's really noticeable looking at LEAF Spy cell-pair charts after a 100% charge), so all else being equal, the '13+ should degrade faster when charged to 100%, but not all else is equal as there have been tweaks to the chemistry so it's hard to say exactly how the batteries will compare.

As far as 100% charging only - my biggest issue is that if I were to do that it would be impossible to avoid leaving it at 100% for extended periods of time - especially on weekends, I may not drive the entire weekend. Or I may drive 50+ miles. It's simply not predictable. Not to mention that TOU schedules generally encourage one to stop charging by 5 AM, that generally leaves 3-5 hours of sitting at full charge every day.

And for people who don't need a full charge and live on top of a hill, they are giving up significant gains in efficiency and increasing brake wear by losing regenerative braking during the initial part of their drive.

A slider with 10% increments from 50-100% like in the Tesla Model S is the way to go.

 

[theds]

I really should've gone with a '13. Didn't think Nissan would be so dumb to remove a feature.

I live on top of a hill and I'd like to leave some room for regen charging going down hill. I couldn't figure out a way to stop charging at 80% or 90% on my 2014 SV. Nissan really should add this option.

Yeah. There were previously choices for 80 and 100% (easiest on the '13) and during the whole Phoenix battery degradation debacle (and likely numerous other times), people have asked Nissan for more charge % choices. Andy Palmer and the other Nissan guy at the Phoenix meeting heard the request...

Instead, they removed it on the '14 :roll:, for reasons already discussed earlier.

 

[TomT]

It's called scamming the EPA (and the consumer)...

I really should've gone with a '13. Didn't think Nissan would be so dumb to remove a feature.

 

[leafedbehind]

It's called scamming the EPA (and the consumer)...

Well I suppose, although I think the EPA is partly responsible here, in their attempt to whittle down range to a single number. I really thought the
"compromise" of averaging 80% and 100% charge range to be rather ridiculous and pathetic, and Nissan's response to that completely unsurprising. The rated range should be based on the maximum, because when you care about range, you're going to charge to 100% or "extended range" or whatever the particular EV calls it.

--Steve

 

[BrockWI]

I don't follow Tesla's much but I wouldn't think they would have removed the lower charge option? How did they deal with the ability for the consumer to choose a charge level?

I agree with Steve. That's like saying on a full tank of gas you car can go 300 miles and now you are forced to fill it up to full each time? Realistically it doesn't matter if the end user chooses not to fill a gasser comptely full so why should it matter if we choose to not fill our BEV's full? The "full" range is all that should count.

 

[dgpcolorado]

I live on top of a hill and I'd like to leave some room for regen charging going down hill. I couldn't figure out a way to stop charging at 80% or 90% on my 2014 SV. Nissan really should add this option.

It isn't precise, but a workaround for this problem is to set the end-time-only timer for your charge to finish after you plan to leave. Since charging stops early — at a time that varies somewhat depending on what the starting charge is and whether or not the climate control timer is set — you will need to experiment a bit to get the SOC about where you want it. But you can manage to leave home with less than a "full tank" pretty easily this way.

For example: if your charge tends to finish about 35 minutes early and you want to leave at 7 AM, you might set the charge end time at 8 AM. Or 8:10 AM. Whatever works.

FWIW, just in case you haven't tried it already. I mention it because some people get locked-in to the idea of start time charging and don't think about how useful end-time-only charging can be.

 

[TomT]

If Nissan was serious about it they could have done what Tesla does, a slider from 50 to 100%. Tesla then gets to use the higher number and their customers get to pick what level of charge they want... So, I consider it a scam on Nissan's part...

It's called scamming the EPA (and the consumer)...

Well I suppose, although I think the EPA is partly responsible here, in their attempt to whittle down range to a single number.

 

[theds]

The only problem is that I don't usually leave before the “off peak" ends.

I live on top of a hill and I'd like to leave some room for regen charging going down hill. I couldn't figure out a way to stop charging at 80% or 90% on my 2014 SV. Nissan really should add this option.

It isn't precise, but a workaround for this problem is to set the end-time-only timer for your charge to finish after you plan to leave. Since charging stops early — at a time that varies somewhat depending on what the starting charge is and whether or not the climate control timer is set — you will need to experiment a bit to get the SOC about where you want it. But you can manage to leave home with less than a "full tank" pretty easily this way.

For example: if your charge tends to finish about 35 minutes early and you want to leave at 7 AM, you might set the charge end time at 8 AM. Or 8:10 AM. Whatever works.

FWIW, just in case you haven't tried it already. I mention it because some people get locked-in to the idea of start time charging and don't think about how useful end-time-only charging can be.

 

[gbarry42]

...they announced a more heat tolerant battery was to be released this April. Then, they created another layer of warranty that would replace the battery if it lost more than 25% of its capacity before 60.000 miles. I can't imagine that they would ask for another problem by eliminating the 80% charge if it were deleterious to the battery.

And the year before, they announced we'd be able to purchase a new battery so we wouldn't have to scrap the car. I don't think that these issues are being solved by making announcements.

I also "can't imagine" they would continue to sell LEAFs in oven toasty cities, especially with this warranty in place, as they will be giving out a lot of free batteries as a consequence. Using common sense to predict Nissan's next move (if they move at all) is a risky endeavor.

The problem was that as the car approached 100% charge, it was heating the battery which could be a problem in some climates. The new version charges that last percent or two at a much slower (and perhaps modified amperage) rate, which gives the battery time to dissipate the heat.

Er, well, if they had a temperature sensor inside the battery (they do), they would know if slowing down the charge was important. Meaning, no slowing down needed in the cold country. Those folks actually would like the battery to warm up before they headed out.

Now that we can watch the battery temperature, we can see just how slowly that changes. Extending the charge an extra hour isn't going to let the battery cool; in fact, unless you can get the efficiency to go up by tapering off the charge rate, you're putting the same amount of heat in whether you do it slowly or all at once. So, good theories, but in the end, not really significant.

 

[dgpcolorado]

The only problem is that I don't usually leave before the “off peak" ends.

It is more of a bother, but there is a solution for that problem too: You need to determine about how much charge you need and set the start and end times for that window. You could do it by empirical observation and iteration, or by calculation. If your commute tends to be the same you could have one timer just set to that time window. If it varies you might need to change the timer daily depending on how many SOC% you need. If your commute is short, being off by ten or twenty percent might not make much difference and you can just keep the SOC somewhere in the middle of the range. [I do this, although I don't have a commute in the usual sense of the term. I charge depending on how much I need later that day or the next (usually for an hour and ten minutes at midday to use my solar generation directly). So it can be done.]

Yes, a nuisance, but it can be done if you care to fuss with it. Would it be nicer if Nissan gave you the ability to set the end charge level, as you (and others) have suggested? Yes, of course. I'm just trying to suggest simple workarounds.