Battery temp management for new leaf

[johnlocke]

The temp throttling I was referring to was for the battery output to the motor being reduced at excessive temps. You would probably never see it unless you were going up a long grade or were trying to run at 90 mph.

[BuckMkII]

Those are OEMs and my cold pressure target is always the Max sidewall pressure. Can't remember the last time I saw a passenger tire with 40 PSI listed. (if ever?)

Heh. When I looked at the new tires I saw the fine print that says "Do not exceed 40 PSI when seating bead" or something to that effect, and stopped reading before the final clause. My excuse is that it was upside down at the time, so reading backwards I was not at my best.

I thought that was weird, since all the other tires I can remember having lately were max around 44 PSI, but I was too dumb to read ALL of the sidewall text.

Time to get out the ol' Zefal Double-Shot floor pump! Not that I need to eke out every mile. We drive the car only 15 to 40 miles per day, almost without exception.

[DaveinOlyWA]

Those are OEMs and my cold pressure target is always the Max sidewall pressure. Can't remember the last time I saw a passenger tire with 40 PSI listed. (if ever?)

Heh. When I looked at the new tires I saw the fine print that says "Do not exceed 40 PSI when seating bead" or something to that effect, and stopped reading before the final clause. My excuse is that it was upside down at the time, so reading backwards I was not at my best.

I thought that was weird, since all the other tires I can remember having lately were max around 44 PSI, but I was too dumb to read ALL of the sidewall text.

Time to get out the ol' Zefal Double-Shot floor pump! Not that I need to eke out every mile. We drive the car only 15 to 40 miles per day, almost without exception.

No worries. What gets me is the HUGE amount of discussion over the dangers of inflating to 44 PSI. People cite stats that haven't been true for decades. Back when tire pressures were 32 or lower, it was easy to understand tire failures. At that low of a target, you only needed to lose a few lbs to be in the danger zone.

We hear about blowouts but how many were caused by overpressure? not many, if any at all... Realize the #1 rule in any of this is Sanity... must have it, plain and simple.

[borugee]

Same dimensions but higher energy density. 40KWH vs 30KWH or 24KWH. Not a huge effect while driving (lots of airflow around the battery) but a substantial difference while charging (longer charge time and no airflow to dissipate heat buildup). Unless you intentionally limit the battery capacity (I.E. 12% to 88%) there will be more heat buildup due to a longer charge time. Plus the fact that you are likely to charge it to 100% from a low state(30% or less). This likely to really problematic if you are DCFC'ing on a trip. With the 30KWH battery, adding 2 temp bars during fast charging is common. I expect it to be worse with 40KWH battery. Add in the heating effect from high discharge rates from freeway driving and long trips encouraged by the longer range battery and you could have a recipe for a disaster.

Does Leaf battery getting cooled from airflow? What I am noticing is once temp go high, it do not seems to come down that easily even when driving. When 2 bars go up during QC, they don't come down ever if you drive slow (ECO).

After left parking it take 24Hrs or so to cool down. I think these batteries are very well insulated.

Can someone explain if there is any air cooling (passive) going on with these Leaf Packs or battery enclosure is fully sealed and no air can get it?

[GerryAZ]

Same dimensions but higher energy density. 40KWH vs 30KWH or 24KWH. Not a huge effect while driving (lots of airflow around the battery) but a substantial difference while charging (longer charge time and no airflow to dissipate heat buildup). Unless you intentionally limit the battery capacity (I.E. 12% to 88%) there will be more heat buildup due to a longer charge time. Plus the fact that you are likely to charge it to 100% from a low state(30% or less). This likely to really problematic if you are DCFC'ing on a trip. With the 30KWH battery, adding 2 temp bars during fast charging is common. I expect it to be worse with 40KWH battery. Add in the heating effect from high discharge rates from freeway driving and long trips encouraged by the longer range battery and you could have a recipe for a disaster.

Does Leaf battery getting cooled from airflow? What I am noticing is once temp go high, it do not seems to come down that easily even when driving. When 2 bars go up during QC, they don't come down ever if you drive slow (ECO).

After left parking it take 24Hrs or so to cool down. I think these batteries are very well insulated.

Can someone explain if there is any air cooling (passive) going on with these Leaf Packs or battery enclosure is fully sealed and no air can get it?

The battery housing is sealed, but highway driving causes enough air flow around the housing to cool it some after QC. In my climate, I actually see battery temperature climb after exiting freeway and driving slower on surface streets (even without QC). If I QC, I will see battery temperature drop while driving, but it drops very slowly at surface street speeds.

[LeftieBiker]

The packs are enclosed in metal but air flows around the metal case. Cooling is fairly minimal except when the outside air is much cooler than the pack temp, and even then, if the core of the pack is hot from QC, it would take hours of gentle driving to cool it.

[DaveinOlyWA]

Same dimensions but higher energy density. 40KWH vs 30KWH or 24KWH. Not a huge effect while driving (lots of airflow around the battery) but a substantial difference while charging (longer charge time and no airflow to dissipate heat buildup). Unless you intentionally limit the battery capacity (I.E. 12% to 88%) there will be more heat buildup due to a longer charge time. Plus the fact that you are likely to charge it to 100% from a low state(30% or less). This likely to really problematic if you are DCFC'ing on a trip. With the 30KWH battery, adding 2 temp bars during fast charging is common. I expect it to be worse with 40KWH battery. Add in the heating effect from high discharge rates from freeway driving and long trips encouraged by the longer range battery and you could have a recipe for a disaster.

Does Leaf battery getting cooled from airflow? What I am noticing is once temp go high, it do not seems to come down that easily even when driving. When 2 bars go up during QC, they don't come down ever if you drive slow (ECO).

After left parking it take 24Hrs or so to cool down. I think these batteries are very well insulated.

Can someone explain if there is any air cooling (passive) going on with these Leaf Packs or battery enclosure is fully sealed and no air can get it?

Yeah, but it depends. The 3 temp sensors, I have seen starting within 2-3º of each other but diverging up to 15º apart after taking to the road which suggests more than radiant cooling going on. I guess it could simply be the coolest sensor being positioned closer to the bottom of the pack maybe?

But all schematics I have seen show no indication of any kind of venting, active passive or otherwise. AFAIC tell, the pack is all but submersible and waterproof

[edatoakrun]

..the pack is all but submersible and waterproof

The pack is designed to be submersible and waterproof, as well as impervious to air.

The pack is cooled primarily by conduction, by the metal to metal contact of the module cases and their attachment points on the unibody and case.

It might be useful to think of the LEAF's lower body as a radiator, which will of course will disperse heat more readily when the temperature differential is higher (lower ambient) and also when there is airflow over the exposed areas.

Remember that the primary thermal management problem in any BEV is in keeping the pack warm enough in cooler conditions to retain efficiency and capacity. A passively managed pack, as on 2011-18 LEAFs, must be designed for optimum operation in its entire anticipated operating temperature range.

...Besides having an effect on battery life, the battery chemistry also affects the internal impedance of each cell.
As has been noted on this forum, the original Tesla MS/X cell exhibits a significantly greater internal impedance
than the Leaf's. So at the same cell currents, the Tesla cells will develop more heat, increasing the necessity
for TMS for the Tesla versus for the Leaf.

BEV designers take varying (by both kW rate and temperature) rates of impedance into account in designing BEV battery packs and drive-trains.

2011-17 LEAF packs depend on this passive heat source for their battery heating needs, to keep the pack higher up in the temperature range, giving higher kWh capacity than that available from colder packs.

A major reason for the observable lower efficiency in m/kWh when driving colder temperatures is the greater amount of energy diverted to pack heating, both when charging and discharging, when the pack is colder.

The presumably larger thermal mass of the larger 2018-on LEAF pack(s) should allow them to retain heat longer, a net positive for operating efficiency.

The lower C rate of the larger packs, during both charge and discharge cycles, should also lower the amount of undesirable heat generated under the relatively unusual conditions (pack temperatures exceeding ~90 F to 100 F) when additional pack heating is undesirable.

So we should expect 2018-on LEAF packs to operate more efficiently and lose capacity at a lower rate than earlier lower kWh packs, even if AESC had made no improvements at all in cell chemistry.

...though, I certainly expect improvements were made.

[LKK]

I read this curious statement in Inside EVs story on the expansion of the Nissan battery plant.

"Editor’s Note: It is our assumption that Nissan will be using LG Chem batteries for the longer range, ~60 kWh/225 mile that arrives later next year as a 2019 model year offering (the ID Concept’s 60 kWh battery was co-developed with LG Chem), and that Nissan’s deal to sell GSR its battery business is also contingent upon them being the sole battery provider (40 kWh) for the 2018 model year LEAF."

I didn't know the 60 kwh battery was going to be produced by LG. LG makes a lot of subsystems for the Bolt including the battery and it's thermal management system. Do you think LG cut Nissan a sweet deal to abandon their own battery and use a 60 kwh battery and thermal management system derived from the Bolt?

[Oils4AsphaultOnly]

I read this curious statement in Inside EVs story on the expansion of the Nissan battery plant.

"Editor’s Note: It is our assumption that Nissan will be using LG Chem batteries for the longer range, ~60 kWh/225 mile that arrives later next year as a 2019 model year offering (the ID Concept’s 60 kWh battery was co-developed with LG Chem), and that Nissan’s deal to sell GSR its battery business is also contingent upon them being the sole battery provider (40 kWh) for the 2018 model year LEAF."

I didn't know the 60 kwh battery was going to be produced by LG. LG makes a lot of subsystems for the Bolt including the battery and it's thermal management system. Do you think LG cut Nissan a sweet deal to abandon their own battery and use a 60 kwh battery and thermal management system derived from the Bolt?

Interesting. But I read that the new Hyundai Kona EV was going to use the same powertrain (motor + inverter) as the bolt!: https://cleantechnica.com/2017/10/06/ko ... range-hot/

So LG's going to enjoy some massive economies of scale by having multiple companies use their batteries and motors.