Nissan LEAF - General

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#1982101 23-Mar-2018 14:22

I guess it's a little more difficult to truly measure the range of an EV outside a test track scenario. In a petrol car, you can drive it till the engine dies, note how far you went, and then put some fuel in from a can to get to a petrol station. If you run your EV to zero you're waiting for a tow truck.

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#1982103 23-Mar-2018 14:23

zenourn:

We have some preliminary results but have more work to do before we publish formal results. More detail is provided in response to comment 3 at https://www.preprints.org/manuscript/201803.0122/v1

For now there are results from 24 kWh Leafs at http://www.electricvehiclewiki.com/Battery_Capacity_Loss#Range_Test_on_Cars_with_Battery_Capacity_Loss

That would seem to indicate that the range corresponds to the SOH pretty closely. So its not likely to be a software glitch but a real battery degradation.

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#1982104 23-Mar-2018 14:29

Elliemay:

I would like to know if anybody has performed tests on actual range (not GOM) at varying SOH readings? What I am getting at is determining what impact a reported drop in SOH has on actual range. In my mind this is the actual crux of the issue - not what some device tells us is an estimated measure of battery health, but what performance the battery will actually provide.

Thanks.

Hi Elliemay, I can confirm that my range from 100% to turtle has gone down by about 10% as my SOH has gone down by 12%.

I am also aware of some testing done by a local dealer who measured how much electrical current was absorbed by serveral Leafs while charging, and it corresponded to the SOH. Cars with lower SOH took less charge to get to 100%.

Its important to note that the BMS on the car determines how and when to start and stop charging, rate of charging and so on, so if it was faulty, it would actually absorb less energy. So if the SOH readings are false compared to the actual chemical state of the battery, it wouldn't matter much, as the car won't accept more charge than it thinks it can hold. So the result is the same, a low SOH means less electricity in your battery at 100% charge.

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#1982107 23-Mar-2018 14:32

zenourn:

Elliemay:

I would like to know if anybody has performed tests on actual range (not GOM) at varying SOH readings? What I am getting at is determining what impact a reported drop in SOH has on actual range. In my mind this is the actual crux of the issue - not what some device tells us is an estimated measure of battery health, but what performance the battery will actually provide.

We have some preliminary results but have more work to do before we publish formal results. More detail is provided in response to comment 3 at https://www.preprints.org/manuscript/201803.0122/v1

For now there are results from 24 kWh Leafs at http://www.electricvehiclewiki.com/Battery_Capacity_Loss#Range_Test_on_Cars_with_Battery_Capacity_Loss

I've put this together as a plot:

Thanks for this. When do you think you will have the test data, as mentioned in number 7 of your response? As the graph provided is for the 24KwH version, and there is a significant difference in the degradation in the estimated SOH between the 24KwH version and the 30KwH, it cannot necessarily be applied to the 30KwH LEAF.

Elliemay

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#1982154 23-Mar-2018 14:48

happyfunball:

Elliemay:

I would like to know if anybody has performed tests on actual range (not GOM) at varying SOH readings? What I am getting at is determining what impact a reported drop in SOH has on actual range. In my mind this is the actual crux of the issue - not what some device tells us is an estimated measure of battery health, but what performance the battery will actually provide.

Thanks.

Hi Elliemay, I can confirm that my range from 100% to turtle has gone down by about 10% as my SOH has gone down by 12%.

I am also aware of some testing done by a local dealer who measured how much electrical current was absorbed by serveral Leafs while charging, and it corresponded to the SOH. Cars with lower SOH took less charge to get to 100%.

Its important to note that the BMS on the car determines how and when to start and stop charging, rate of charging and so on, so if it was faulty, it would actually absorb less energy. So if the SOH readings are false compared to the actual chemical state of the battery, it wouldn't matter much, as the car won't accept more charge than it thinks it can hold. So the result is the same, a low SOH means less electricity in your battery at 100% charge.

And yet, within 5 minutes of me asking the question, someone provided real world evidence that the SOH, at 78%, has had little or no impact on the actual (not estimated) range relative to a new 30KwH Leaf. I know it is only one example, but I think enough to think critically.

happyfunball

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#1982169 23-Mar-2018 15:01

Elliemay:

And yet, within 5 minutes of me asking the question, someone provided real world evidence that the SOH, at 78%, has had little or no impact on the actual (not estimated) range relative to a new 30KwH Leaf. I know it is only one example, but I think enough to think critically.

Based on one example, I think that would be wishful thinking rather than critical. :) It would be pretty magical if a Li-ion battery did not degrade over time.

Another way of looking at it is, how likely is it that the BMS is wildly inaccurate at estimating the battery capacity (despite being responsible for charging, balancing and measuring voltage on the cells) and in fact all these cars with reported problems are just fine?

Occams razor says take the simpler explanation, which is that these batteries (which are supposed to degrade over time) are degrading a bit faster than expected.

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#1982170 23-Mar-2018 15:03

Elliemay:

And yet, within 5 minutes of me asking the question, someone provided real world evidence that the SOH, at 78%, has had little or no impact on the actual (not estimated) range relative to a new 30KwH Leaf. I know it is only one example, but I think enough to think critically.

Range is very dependent on speed, temperature, wind, and traffic so for any range comparison to be meaningful all those factors need to be controlled for. Comparing the EPA range of a new Leaf to the range of a Leaf with a SoH of 78% is only meaningful if the Leaf with a SoH of 78% also used the EPA protocol.

I can get 160 km with my 24 kWh Leaf with still some percent left over in city driving. But then only max 110 km range if going 100 km/hr.

SaltyNZ

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#1982174 23-Mar-2018 15:05

Elliemay:

And yet, within 5 minutes of me asking the question, someone provided real world evidence that the SOH, at 78%, has had little or no impact on the actual (not estimated) range relative to a new 30KwH Leaf. I know it is only one example, but I think enough to think critically.

It's not only one example, it's only one datapoint from that example. The last 20km or so of that particular day I was driving in Eco mode at about 75km/hr, not in a normal 100km/hr natural driving mode. Difficult to say exactly how much difference that makes.

Another data point: ChargeNet terminals send you an SMS at beginning and end. On one particular day I began charging at 22% and it finished (on its own) having delivered 14.3kWh. If 14.3kWh is 78% of the battery capacity then my actual capacity is ~18.3kWh. Assuming it stopped at 80% charge, then 14.3kWh is 58% capacity, meaning my actual capacity is ~24.6kWh. The 24.6kWh figure agrees fairly closely with an estimate SoH of ~80% for a 30kWh battery.

Edit: A number.

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Elliemay

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#1982179 23-Mar-2018 15:14

My point is, performing a study without considering all possible, reasonable questions/nuances is not a complete study. From the limited responses today, everyone is happy to believe that actual range does drop with a drop in estimated SOH, based purely on theory.

I am not saying it doesn't, but the Flip the Fleet study is missing this important aspect. Hopefully they will have this information soon, as indicated.

Elliemay

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#1982181 23-Mar-2018 15:20

SaltyNZ:

Elliemay:

And yet, within 5 minutes of me asking the question, someone provided real world evidence that the SOH, at 78%, has had little or no impact on the actual (not estimated) range relative to a new 30KwH Leaf. I know it is only one example, but I think enough to think critically.

It's not only one example, it's only one datapoint from that example. The last 20km or so of that particular day I was driving in Eco mode at about 75km/hr, not in a normal 100km/hr natural driving mode. Difficult to say exactly how much difference that makes.

Another data point: ChargeNet terminals send you an SMS at beginning and end. On one particular day I began charging at 22% and it finished (on its own) having delivered 14.3kWh. If 14.3kWh is 78% of the battery capacity then my actual capacity is ~18.3kWh. Assuming it stopped at 80% charge, then 14.3kWh is 58% capacity, meaning my actual capacity is ~24.6kWh. The 24.6kWh figure agrees fairly closely with an estimate SoH of ~80% for a 30kWh battery.

Edit: A number.

Thanks for the additional info! I am even more impressed now that you have said only 20km of that 150km trip was at 75km/hr, which I assume from what you have said means that you were doing 100km/hr for the other 130km?

SaltyNZ

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#1982185 23-Mar-2018 15:27

Elliemay:

Thanks for the additional info! I am even more impressed now that you have said only 20km of that 150km trip was at 75km/hr, which I assume from what you have said means that you were doing 100km/hr for the other 130km?

No, it just means that I wasn't being especially careful to drive to extend range the rest of that day. In fact the rest of that was a normal commute day for me, which means part of it was 100km/hr, but a lot of it was naturally 70km/hr or less anyway due to traffic. On the way home from Newmarket to Warkworth, it's not till you get past Silverdale that you can drive at unrestricted speeds.

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#1982329 23-Mar-2018 18:14

A controlled discharge test is the only true way of measuring a battery's true capacity. If we run a car on a dynometer with the cruse control set to say 60km/hr and let it run until the car turtles we can measure the total power output from the battery and this is a test we can repeat regardless of weather or other external influences.
Ideally we need a bench mark in the form of a car that is still reporting 100% SOH to compare against and then take vehicles reporting various vales of SOH and compare. I'm keen to give it a go if others are.

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zenourn

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#1982346 23-Mar-2018 20:29

dirtbag: A controlled discharge test is the only true way of measuring a battery's true capacity. If we run a car on a dynometer with the cruse control set to say 60km/hr and let it run until the car turtles we can measure the total power output from the battery and this is a test we can repeat regardless of weather or other external influences.
Ideally we need a bench mark in the form of a car that is still reporting 100% SOH to compare against and then take vehicles reporting various vales of SOH and compare. I'm keen to give it a go if others are.

We have done some test with a dyno but it wasn't ideal so far. First car didn't have cruise control so had to sit there with foot at constant position on accelerator (not an easy task!) and then the second car did have cruise control but it didn't interact well with the dyno. But the bigger issue is to calculate energy supplied you need accurate measurements of current from the HV battery and the internal current sensor possibly isn't that accurate.

We are working on a method that resolves the current accuracy issue and are planning to publish it formally so anyone can repeat it. Although there is a lot of anecdotal support that SoH correlates with energy capacity and range there is a surprising lack of proper scientific data.

numberonekiwi

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#1983565 26-Mar-2018 15:41

I am not sure if this is any help with the 30Kw/h battery. Around Christmas / New Year I was using a 30KWh LEAF I think SOH was low 90's a couple of weeks later LEAF spy said 85% I did however do a trip from my house in Tauranga if anyone knows Tauranga and the BP summit that is a close enough location. I drove from there to Tairua ( can not remember my SOC when arriving but left here 100% ) I took 11.6 Kw with the time being 16:41 to charge that was to 80% SOC however if you run those stats through greenrace I should of arrived at 31% battery remaining.I can provide the other charges I did along the coromandel loop to arrive a home with no dash for the last 5 kms. If that is the true usage of power I should be able to do this trip in a Gen1 with 17.6KW/h remain on the battery but greenrace shows that if I did I would have -10% I would not make it.

KiwiME

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#1983589 26-Mar-2018 16:15

zenourn:.. second car did have cruise control but it didn't interact well with the dyno.

Presumably because the dyno was also running in a speed control mode. You would need to use a constant torque (or tractive effort) mode. You could determine a suitable torque value by measuring motor current at your 60kph under actual flat road conditions (no wind, or average of opposing runs) and then matching that current while on the dyno with a corresponding fixed torque or tractive effort value. That would effectively zero-out the current error and only be limited in accuracy by the displayed resolution.

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