2019 Leaf battery overheating

[OrientExpress]

The present U.S. BMS firmware with reduced charging rates results in battery temps approaching 120-125 F for long charging
times. Those temperatures will increase battery degradation. If the BMS is re-flashed for increased battery charging rates,
the long term Leaf battery degradation will be further compounded. For those with leases, that problem is most likely of little
concern, but for those who purchased their Leaf, that potentially should be of a major concern. The battery temperature
problem is potentially more problematic in the U.S. versus Europe, given the difference in the average summer temperatures
and the longer typical inter city drives requiring more sequential charging.

Not exactly correct. The normal operating temperature of the new batteries is between 30F and 120F. Temperatures close to 120F may be mitigated by slower charging speeds and a eco+ like throttle response based on throttle demand, and somewhere above 125F will trigger a power reduction to the motor and the car will enter into a turtle mode. This also happens below 30F.

While I respect the analysis, its major flaw is that it treats the newer 40 and 62kW batteries as if they have the same characteristics of the obsolete lithium manganese oxide 24 and 30 kW batteries. They do not and the assumption that they do is a serious flaw of the analysis. The nickel manganese cobalt cells of the new battery are much more heat tolerant and can run reliably at temperatures up to 120F. Ongoing testing of these newer batteries at Nissan hot weather proving grounds around the world that started at least three years ago provide significance confidence in their durability. Of course there will always be edge cases, and the Durability and degradation warranty will take care of those edge cases.

At temperatures about between 115F and 120F the BMS will begin to mitigate harm to the battery by reductions in charging speed and performance. The driving style of the operator has a lot to do in how and when these adjustments are made.

There is plenty of publicly available information available discussing the new LEAF batteries, and I would encourage that everyone reading this to add those documents to your reading lists.

Here are a few articles to help you get started:
https://insideevs.com/news/338432/nissan-leaf-40-kwh-battery-deep-dive/

https://www.greencarreports.com/news/1117928_2018-nissan-leaf-battery-technology-a-deep-dive

I have a feeling that many of you will reject and mock this assessment, and that is certainly your prerogative, but it is factual rather than conjecture.

I would also encourage you to compare and contrast the performance and heat tolerance of the current 40 and 62 kW batteries with those that are available from other marques, especially how they throttle their fast charging. I think you will find that they are very similar to the LEAF even though they have active battery cooling.

https://insideevs.com/news/338777/lets-look-at-fast-charging-curves-for-popular-electric-cars/

 

[ChozoGhost79]

I'll try a drive and DC fast charge at some point, and check temps with LEAFspy. My experience is a 100 ish mile drive, DC fast charge, and another 100 ish mile drive will find my 62 KWH pack at the very top of normal operating temp range on the temp readout, with the resulting reduction of charge power. A Tesla Model 3 owner I know can count on consistent charge times because the liquid cooling removes the heat generated by charging.

 

[OrientExpress]

I'll try a drive and DC fast charge at some point, and check temps with LEAFspy. My experience is a 100 ish mile drive, DC fast charge, and another 100 ish mile drive will find my 62 KWH pack at the very top of normal operating temp range on the temp readout, with the resulting reduction of charge power. A Tesla Model 3 owner I know can count on consistent charge times because the liquid cooling removes the heat generated by charging.

I think that you will find that at about 200 miles your car will consistently set the charge rate at about 51%-67% of the first charge power rate. If your top rate was 35kW, then expect about 18 kW on the 2nd or third. 10 minutes of cool down time between driving and actually starting the charge can do wonders at letting the battery recover somewhat. I've increased the charge rate to 24kW with that short breather time. It also helps to keep your road speed under 80.

 

[ChozoGhost79]

I will try giving the car a break before starting fast charging. With LEAFSpy I can get an idea how quickly the battery can cool when resting.

 

[Nubo]

First DCFC is at expected charge rates, but the second after a about 100 mile drive, the temperature display in the car was at the top of the normal operating range, and DCFC was throttled down to about 19-20 KW. This happened the rest of the trip as well.

This appears to be Nissan's idea of 'Normal and acceptable.'

Yep. All engineering is a balance of compromises. This configuration allows a certain combination of price, range, and duty. It will be satisfactory to some but not all prospective EV buyers. For owners that don't regularly need multiple QC per drive, a passive system does offer definite benefits.

But I think sooner rather than later, Nissan will find it necessary to institute an active thermal management strategy to maintain performance parity in the market, unless they have some significant battery improvements up their sleeves.

 

[WetEV]

Yep. All engineering is a balance of compromises. This configuration allows a certain combination of price, range, and duty. It will be satisfactory to some but not all prospective EV buyers. For owners that don't regularly need multiple QC per drive, a passive system does offer definite benefits.

But I think sooner rather than later, Nissan will find it necessary to institute an active thermal management strategy to maintain performance parity in the market, unless they have some significant battery improvements up their sleeves.

When you have a cost advantage and other advantages, performance may not matter that much. The reason why Toyota Camry is the best selling car in the USA isn't 0-60 times.

 

[OrientExpress]

In looking close at the Infiniti and Nissan BEV concepts that have been making the rounds over the last year, a different battery cooling system is certainly a possibility for some models.

 

[SageBrush]

At temperatures about between 115F and 120F the BMS will begin to mitigate harm to the battery by reductions in charging speed and performance.

Define 'harm.'
Quantify 'mitigation.'
Define 'normal.'

And tell us where the temp readings come from. Do the green, yellow, red colors talk to you ?

 

[DaveinOlyWA]

At temperatures about between 115F and 120F the BMS will begin to mitigate harm to the battery by reductions in charging speed and performance.

Define 'harm.'
Quantify 'mitigation.'
Define 'normal.'

And tell us where the temp readings come from. Do the green, yellow, red colors talk to you ?

You are asking a lot. Let me state that a reduction in performance was not applicable to me at 128º. The reduction in charging speed happens below 90º making his entire statement suspect.

 

[OrientExpress]

It's not a black and white number, much depends on the variability of how the driver is operating the vehicle, and may be very subtle. In addition the actual temperature of the battery is constantly moving. A single point measurement may or may not be relevant.

 

[SageBrush]

It's not a black and white number

That is not right. It is a green, yellow or red number in your world. :lol: :lol:

 

[WetEV]

In addition the actual temperature of the battery is constantly moving. A single point measurement may or may not be relevant.

I'd like a number on the dashboard. How can I get that?

 

[DaveinOlyWA]

In addition the actual temperature of the battery is constantly moving. A single point measurement may or may not be relevant.

I'd like a number on the dashboard. How can I get that?

LEAF Spy.

Now there are "some" who feel that LS is nothing but a child's toy not to be taken seriously and I have no comment on that. But in correlating LS temperature readings which are "not" one of the derived measurements from the bus, with the actual temperature (bar slider pip) display, I find the range of reading variances to be quite small which is the reason I put on the Temperature Bar blog.

What I don't see is a significant (if any) variance in expected charging speed per any specific battery pack temperature. Again, the speed is very predictable.

But if using one's "Holy Grail of acceptability" Nissan instrumentation, we find that the 12 temperature displays are not created equally despite them all being the same size. We also see this variance in the SOC meter at various levels when the hidden reserve is missing at high SOCs but grows continuously as the SOC goes down.

Now we can chose to use Nissan's "indisputable" dash readings or go play with toys!

Your choice.

 

[ChozoGhost79]

In addition the actual temperature of the battery is constantly moving. A single point measurement may or may not be relevant.

I'd like a number on the dashboard. How can I get that?

LEAF Spy.

Now there are "some" who feel that LS is nothing but a child's toy not to be taken seriously and I have no comment on that. But in correlating LS temperature readings which are "not" one of the derived measurements from the bus, with the actual temperature (bar slider pip) display, I find the range of reading variances to be quite small which is the reason I put on the Temperature Bar blog.

What I don't see is a significant (if any) variance in expected charging speed per any specific battery pack temperature. Again, the speed is very predictable.

But if using one's "Holy Grail of acceptability" Nissan instrumentation, we find that the 12 temperature displays are not created equally despite them all being the same size. We also see this variance in the SOC meter at various levels when the hidden reserve is missing at high SOCs but grows continuously as the SOC goes down.

Now we can chose to use Nissan's "indisputable" dash readings or go play with toys!

Your choice.

LEAF Spy sure does give you a lot more information than you can get in the car. I'm surprised I didn't try it earlier.

 

[smkettner]

It's not a black and white number, much depends on the variability of how the driver is operating the vehicle, and may be very subtle. In addition the actual temperature of the battery is constantly moving. A single point measurement may or may not be relevant.

It is pretty black and white number for the BMS to limit charging power.

 

[WetEV]

In addition the actual temperature of the battery is constantly moving. A single point measurement may or may not be relevant.

I'd like a number on the dashboard. How can I get that?

LEAF Spy.

Not on the dashboard. Still, not a bad workaround, I've had this or similar for years.

 

[OrientExpress]

It is pretty black and white number for the BMS to limit charging power.

For charging the LEAF, as with every other BEV today, there are a variety of variables that will determine what the charge profile will be. While that is absolute, the way those variables are applied, is variable.

The challenge for the operator is to develop the skills that allows the maximum charge rate. But even with that there will always be a reduction in charging power over a charging session to maximize the batteries health.

 

[smkettner]

Sure. And ALL things being equal there is a point where the battery temperature will limit the charge rate.
Sorry the rest is just secret proprietary BS.

A battery cooling system would mitigate the high temperature reduction in charging because the battery would be at a lower temperature.
No rocket science needed here.

 

[OrientExpress]

Yep, an active system will cool a battery as will a passive system. If a cooling system is important for you then perhaps it’s time to move to a BEV that has a system that you would be more comfortable with and suits your driving style. A LEAF is certainly not for everyone.

 

[lorenfb]

The present U.S. BMS firmware with reduced charging rates results in battery temps approaching 120-125 F for long charging
times. Those temperatures will increase battery degradation. If the BMS is re-flashed for increased battery charging rates,
the long term Leaf battery degradation will be further compounded. For those with leases, that problem is most likely of little
concern, but for those who purchased their Leaf, that potentially should be of a major concern. The battery temperature
problem is potentially more problematic in the U.S. versus Europe, given the difference in the average summer temperatures
and the longer typical inter city drives requiring more sequential charging.

Not exactly correct. The normal operating temperature of the new batteries is between 30F and 120F. Temperatures close to 120F may be mitigated by slower charging speeds and a eco+ like throttle response based on throttle demand, and somewhere above 125F will trigger a power reduction to the motor and the car will enter into a turtle mode. This also happens below 30F.

While I respect the analysis, its major flaw is that it treats the newer 40 and 62kW batteries as if they have the same characteristics of the obsolete lithium manganese oxide 24 and 30 kW batteries. They do not and the assumption that they do is a serious flaw of the analysis. The nickel manganese cobalt cells of the new battery are much more heat tolerant and can run reliably at temperatures up to 120F. Ongoing testing of these newer batteries at Nissan hot weather proving grounds around the world that started at least three years ago provide significance confidence in their durability. Of course there will always be edge cases, and the Durability and degradation warranty will take care of those edge cases.

At temperatures about between 115F and 120F the BMS will begin to mitigate harm to the battery by reductions in charging speed and performance. The driving style of the operator has a lot to do in how and when these adjustments are made.

Firstly, the battery resistance tests results inferred that the battery resistances of the 42kWh/62kWh Leafs were most likely of a different
battery chemistry than the earlier Leafs, given the higher than expected battery resistances. You have confirmed this, although not good
news that these later batteries will develop more heat while charging, we now have a better understanding.

So a Leaf driver needs to monitor his driving speed to avoid high battery temps, right? That's been stated by some on MNL and is
indicative of a marginal battery chemistry compared to earlier Leafs, a significant negative.

Where are the the long term data analyses, i.e. links, to corroborate the above later battery improvements to withstand higher
temperatures? Please avoid the hyperbole, e.g. "Nissan has stated such"! Inferences of significant improvements by Nissan and
et al won't suffice without longitudinal data.

There is plenty of publicly available information available discussing the new LEAF batteries, and I would encourage that everyone reading this to add those documents to your reading lists.

Here are a few articles to help you get started:
https://insideevs.com/news/338432/nissan-leaf-40-kwh-battery-deep-dive/

You're referring to this:

• 192 cells (nickel manganese cobalt NMC instead lithium manganese oxide cells LMO)
• 24 modules (8 cells per module instead of 4 cells per module)
• 40 kWh capacity (real value is around 39.5 kWh and only 37 kWh or less is available)
• output power increased to over 110 kW (110 kW is peak power of electric motor - previously it was 80 kW)
• charging power is lower than in case of 30 kWh battery - see comparison here - to prevent battery degradation we believe

Somewhat contradictive to your basic argument that the later battery chemistry is an improvement.

And this key point:

The lack of liquid thermal management system seems to be the biggest drawback of Nissan EVs and only time will tell how long the new batteries will last, especially in hot climates. In Norway, Canada or even the UK, there are not many reported problems compared to areas like Arizona, Italy or Spain.

What you have written is not very compelling nor corroborative! Again, where's Nissan's long term analysis of the new chemistry with regard
to heat degradation? Having to reduce the charging current over earlier Leafs is not indicative of improved battery chemistry.
Many on MNL question your credibility. Hopefully, what you've posted doesn't result in 40kWh/62kWh Leaf owners damaging their
batteries because of misinformation.