Early range decline?

[twingo]

I drive the same way to work each day and usually play a little game to see if I can get my remaining range gauge to show 90 miles at a certain point along the way and 80 when I pull into the parking lot. For the first 2.5 months of ownership, I could achieve both numbers 85~90% of the time. Then I went on vacation for a week with the car sitting the garage. Since I returned about 6 weeks ago, I can no longer achieve those numbers. The typical day is more like 82 and 72. I have about 3,500 miles on the car now. Is this an early sign of battery degradation?

 

[TomT]

More likely just a subtle change in traffic conditions or driving conditions or driving style...

I drive the same way to work each day and usually play a little game to see if I can get my remaining range gauge to show 90 miles at a certain point along the way and 80 when I pull into the parking lot. For the first 2.5 months of ownership, I could achieve both numbers 85~90% of the time. Then I went on vacation for a week with the car sitting the garage. Since I returned about 6 weeks ago, I can no longer achieve those numbers. The typical day is more like 82 and 72. I have about 3,500 miles on the car now. Is this an early sign of battery degradation?

 

[Stoaty]

I don't know what that means. My range on starting the day was consistently 116-118 miles (due to a long downhill drive before getting home). Recently it has dropped to 110 miles. I have owned my Leaf about 3 months. I always charge to 80%. Wondering whether a 100% charge with the battery balancing that occurs afterward might restore my previous "guesstimate".

PS my driving style has actually increased my average miles/KWh over the last few weeks, so if anything the guesstimate should be higher.

 

[twingo]

More likely just a subtle change in traffic conditions or driving conditions or driving style...

I drive the same way to work each day and usually play a little game to see if I can get my remaining range gauge to show 90 miles at a certain point along the way and 80 when I pull into the parking lot. For the first 2.5 months of ownership, I could achieve both numbers 85~90% of the time. Then I went on vacation for a week with the car sitting the garage. Since I returned about 6 weeks ago, I can no longer achieve those numbers. The typical day is more like 82 and 72. I have about 3,500 miles on the car now. Is this an early sign of battery degradation?

Actually, there is almost no traffic on the route I take, so I can pretty easily duplicate the driving variables the exact same way each day.

 

[garygid]

We THINK that the warmer temperatures of the Battery Pack (these warmer days, evenings, and nights) make the LEAF charge (fill) the battery with a bit less energy (than colder conditions). As winter approaches, try to see if your "range" returns. Perhaps keep a log of evening or night-time temps.

You might even want an "SOC" meter when we add temperature display to it.

 

[TomT]

Has the ambient temperature changed appreciably? Anecdotally, this also seems to affect the pack capacity and may be what you are seeing... If it is warmer there now, that may account for it.

I honestly have not been monitoring mine close enough that I can make any judgement on temp versus charge... Plus, my driving and traffic conditions are so variable that it would be hard for me to draw any concrete conclusions anyway...

I don't know what that means. My range on starting the day was consistently 116-118 miles (due to a long downhill drive before getting home). Recently it has dropped to 110 miles. I have owned my Leaf about 3 months. I always charge to 80%. Wondering whether a 100% charge with the battery balancing that occurs afterward might restore my previous "guesstimate".
PS my driving style has actually increased my average miles/KWh over the last few weeks, so if anything the guesstimate should be higher.

 

[Stoaty]

Has the ambient temperature changed appreciably? Anecdotally, this also seems to affect the pack capacity and may be what you are seeing... If it is warmer there now, that may account for it.

No, it has cooled significantly from 2-3 weeks ago, during which time it was 15-20 degree F. warmer. When I came out to my car about 6:30 PM today ambient temperature was about 78 degrees. A couple of weeks ago it was 95 degrees at the same time. The temperature in my underground parking garage at home is usually around 65-70 degrees (guesstimate, not measured), as I live about 4 miles from the coast. Work is in the San Fernando Valley where it was quite hot for a couple of weeks, but a lot cooler the last 4 days or so.

 

[SanDust]

Could be a sign of some degradation. Hopefully you didn't charge to 100% before leaving it for a week. That would not be good. Could of course be something else entirely but it sounds odd.

Sloaty -- In your case it's probably just the temperature. While Gary is right about cold allowing for more charge, when driving the hotter the better, within limits. You'll get much more range when it's hot than when it's cold. Your charging temperature has probably remained the same, but the higher ambient temperatures during your drive allowed the battery to provide more energy and reduced all forms of losses during your drive. Think of it like living at altitude and training at seal level -- maximizes performance.

 

[TonyWilliams]

I had a similar thought recently, and took the car in for a checkup. It turned out to be two things; the high quality Blink charger EVSE that Ecotality sells for $3000 only charged my LEAF to about 85%, instead of 100%.

The other observation, now that the temperatures have come down this week, is that my range is right back on track. Which means there are probably two issues:

A) The higher temperatures limits the capacity of the battery (as we see in the reduced SOC numbers) and..

B) The battery's actual performance is reduced with higher ambient temperatures.

I wonder how a Volt, with active liquid cooling, would handle temperature changes?

 

[GeekEV]

I had a similar thought recently, and took the car in for a checkup. It turned out to be two things; the high quality Blink charger EVSE that Ecotality sells for $3000 only charged my LEAF to about 85%, instead of 100%.

Was that just a fluke? Perhaps it rebooted before finishing charging? Or is it repeatable?

 

[IBELEAF]

That's not degradation, just too many factors even when you think it should be the same. For me range has improved when temps drops.

 

[TonyWilliams]

Was that just a fluke? Perhaps it rebooted before finishing charging? Or is it repeatable?

The Blink has had several "flukes", so I'm going to guess it will repeat :?

 

[SanDust]

B) The battery's actual performance is reduced with higher ambient temperatures.

I wonder how a Volt, with active liquid cooling, would handle temperature changes?

Battery performance should be better at higher temperatures since heat acts like a catalyst in any chemical reaction.

Seems like losses attributable to cold weather outweigh battery performance. Although the Volt heats the battery with the gas engine when the temperature falls below something like 32F, thus ensuring decent battery performance, Volt drivers who are getting 40-45 miles of EV range now got 25-30 miles of EV range last winter. That's a big difference.

 

[Stoaty]

Could be a sign of some degradation. Hopefully you didn't charge to 100% before leaving it for a week. That would not be good. Could of course be something else entirely but it sounds odd.

No, I charged to 100% for the drive home from Fontana Nissan. Any time I am gone for a week I leave the Leaf at about 50% charge.

Sloaty -- In your case it's probably just the temperature. While Gary is right about cold allowing for more charge, when driving the hotter the better, within limits. You'll get much more range when it's hot than when it's cold. Your charging temperature has probably remained the same, but the higher ambient temperatures during your drive allowed the battery to provide more energy and reduced all forms of losses during your drive. Think of it like living at altitude and training at seal level -- maximizes performance.

That could the explanation. I am not worried about it, just curious. I will charge to 100% this weekend and see if that has any effect on the guesstimate after my regular commute.

 

[Herm]

This will be the first question that will come up at the first sign of trouble, for the next few years. We need a test that determines remaining battery capacity to some degree of accuracy.. I doubt 1% is possible. How do the few existing BEVs handle this issue?

Eventually a 3rd party will connect the battery to an external load and just cycle it fully (not as easy to do as you think), or perhaps Nissan will share the information that is stored in the BMS.. or perhaps its not stored in the BMS at all. How can you sell/buy a used Leaf without that information?.. How about buying a used battery?.. Does Nissan have any shop procedures/equipment for testing the battery?.. Supposedly GM dealers can test the Volt's battery and it can take 24 hours to do so.

I need to breathe

Maybe one day we will be able to buy used Nissan certified batteries "with remaining capacity of 19.52kwh" and stored properly.

 

[twingo]

We THINK that the warmer temperatures of the Battery Pack (these warmer days, evenings, and nights) make the LEAF charge (fill) the battery with a bit less energy (than colder conditions). As winter approaches, try to see if your "range" returns. Perhaps keep a log of evening or night-time temps.

You might even want an "SOC" meter when we add temperature display to it.

I'm also in So. Ca. and think of this area as having little temperature variation that would be negligible to these issues, but I don't know how sensitive the battery can be. I have never noticed the battery temperature gauge move one way or the other. I only charge to 80% beginning at midnight. I have an engineering background and have a grasp of dupicating conditions each day to minimize the variables, so I know everything I have been doing is very consistent on a daily basis. My drive in through a back-country winding road. I'm looking forward to see if cooler evenings matter and may do the "SOC" with temp display to gather some more data.

 

[twingo]

This will be the first question that will come up at the first sign of trouble, for the next few years, we need a test that determines remaining battery capacity to some degree of accuracy.. I doubt 1% is possible. How do the few existing BEVs handle this issue?

Eventually a 3rd party will connect the battery to an external load and just cycle it fully (not as easy to do as you think), or perhaps Nissan will share the information that is stored in the BMS.. or perhaps its not stored in the BMS at all. How can you sell/buy a used Leaf without that information?.. How about buying a used battery?.. Does Nissan have any shop procedures/equipment for testing the battery?.. Supposedly GM dealers can test the Volt's battery and it can take 24 hours to do so.

I need to breathe

Maybe one day we will be able to buy used Nissan certified batteries "with remaining capacity of 19.52kwh" and stored properly.

I'm sure the #1 factor to determine resale value will be the battery capacity and an accurate way of measuring it wil be crucial to the buyer.

 

[HighDesertDriver]

This will be the first question that will come up at the first sign of trouble, for the next few years, we need a test that determines remaining battery capacity to some degree of accuracy.. I doubt 1% is possible. How do the few existing BEVs handle this issue?

I can find and post the data, but it will take one of you more EE-minded folks to see how this might apply to the Leaf. The following post came up on the RAV4-EV board yesterday. The RAV owners seem to focus initially on cell resistance and secondarily on other issues. Fortunately, after 10 years of operation, they have developed a few methods and devices for getting this data. Perhaps Paul Scott can elaborate from his experience?

FYI: New battery packs are not available. "Replaced" when discussing RAV4-EV battery packs can mean either that the pack was replaced with another overhauled pack or was overhauled and put back in. It depends on the available stock and time available. Both are done at a single source in Sacramento using expensive cell cycling equipment to rejuvenate degraded cells and a stock of reclaimed cells from retired vehicles to replace hopeless cells. The car must be shipped to a dealer in the Sacramento area to have this work done. . . even if vehicle is located in Florida. Ouch!

One of the potential buyers for my Rav4 suggested that I do an experiment with Rav4info to give him a better idea of the pack health. He wanted me to watch peak current and min voltage during maximum acceleration.

I did three trials at a freeway onramp, and the one with the highest current was this one:

Stopped: 303.7V, 0.9A
Max Accel: 270V, 206A
Delta: 33.7V, 205.1A
Pack resistance (deltaV/deltaI): 164.3 mohm
Avg cell resistance (max/24): 6.8 mohm

Tests were done at SOC of 65-70%. I have heard that pack resistances are fairly insensitive to SOC except when close to full or empty (20-80% should be OK).

Ron also tested my pack with the scan tool, and found 14 cells at 6 mohm and 10 at 7 mohm for an average of 6.4 mohm.

These numbers are pretty close given the scan tool has only one significant digit. I think the Rav4Info test is a simple, excellent test of the battery health. My pack is still the original with 95K miles on it and this should mean that it has another 25-50K miles before needing to be replaced.

It would be interesting to get the same measurements from others with Rav4Info. Especially interesting would be from some who are about to replace their packs and some who just replaced them. Even better would be to have several cars record the deltaV and deltaI every 5 or 10K miles until the pack needs replacing. That would give all of us an idea on how many miles we have left on the current pack.

 

[cdub]

I drive the same way to work each day and usually play a little game to see if I can get my remaining range gauge to show 90 miles at a certain point along the way and 80 when I pull into the parking lot. For the first 2.5 months of ownership, I could achieve both numbers 85~90% of the time. Then I went on vacation for a week with the car sitting the garage. Since I returned about 6 weeks ago, I can no longer achieve those numbers. The typical day is more like 82 and 72. I have about 3,500 miles on the car now. Is this an early sign of battery degradation?

No. Those #s are meaningless. It's just that you're probably driving slightly different here and there.

 

[SanDust]

That could the explanation. I am not worried about it, just curious. I will charge to 100% this weekend and see if that has any effect on the guesstimate after my regular commute.

I'm thinking the car can top balance with an 80% charge but maybe not. Will be interesting to see how this works for you.

BTW the question about leaving the car with 100% charge was for the OP. Should have been more clear. He's in Escondito where the garages can get very hot. Given how little top end the battery has when charged to 100%, leaving it stored in the heat charged like this would not be conducive to long life.