TexasLeaf
Posts: 22
Joined: Wed Mar 21, 2018 5:37 am
Delivery Date: 21 Mar 2018
Leaf Number: 303111

Re: Using speed to control battery temperature

Sat Jun 02, 2018 8:37 am

SageBrush wrote: An EV is a different animal entirely. Heating the cabin is via battery energy, albeit at a COP > 1.0.
If the intent is cool off the battery, nothing good will come of this maneuver.


Heat pumps usually have a COP of 3 or 4, if they couldn't get a COP better than 1 then Nissan would have just put in an electric resistance heater. I have already proven that the heat pump cools the motor compartment!! Maybe the heat pump won't help cool the battery but conjecture like this doesn't help answer any questions.

SageBrush
Posts: 2397
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: Colorado

Re: Using speed to control battery temperature

Sat Jun 02, 2018 8:42 am

TexasLeaf wrote:Maybe the heat pump won't help cool the battery.

No maybe about it.
2013 Model 'S' with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Car is now enjoying an easy life in Colorado
3/2018: 58 Ahr, 28k miles

TexasLeaf
Posts: 22
Joined: Wed Mar 21, 2018 5:37 am
Delivery Date: 21 Mar 2018
Leaf Number: 303111

Re: Using speed to control battery temperature

Sat Jun 02, 2018 8:53 am

SageBrush wrote:[No maybe about it.


More speculation.

SageBrush
Posts: 2397
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: Colorado

Re: Using speed to control battery temperature

Sat Jun 02, 2018 9:51 am

TexasLeaf wrote:
SageBrush wrote:No maybe about it.

More speculation.

Indeed. Similar to the effect of jumping off a cliff.
2013 Model 'S' with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Car is now enjoying an easy life in Colorado
3/2018: 58 Ahr, 28k miles

WetEV
Posts: 2066
Joined: Fri May 04, 2012 8:25 am
Delivery Date: 16 Feb 2014
Location: Near Seattle, WA

Re: Using speed to control battery temperature

Sat Jun 02, 2018 7:25 pm

SageBrush wrote:Indeed. Similar to the effect of jumping off a cliff.

Life of the party, I see.
WetEV
#49
Most everything around here is wet during the rainy season. And the rainy season is long.
2012 Leaf SL Red (Totaled)
2014 Leaf SL Red

TexasLeaf
Posts: 22
Joined: Wed Mar 21, 2018 5:37 am
Delivery Date: 21 Mar 2018
Leaf Number: 303111

Re: Using speed to control battery temperature

Tue Jun 05, 2018 3:08 am

I performed a test last weekend, the goal of the test was to see how much CHAdeMO charging increased battery temperature. I still don't have LeafSpy so I had to depend on the Leaf battery temperature gauge. This was a short test and I only drove about 230 miles but I found it quite informative.

I went through two full charge sessions driving at 60 mph the whole time without running the air conditioner or heat pump. I started the drive portions of the test with approximately 80% charge and I drove until the battery was near the 20% level. I then charged the battery back up to the 80% level.

At the beginning of the first drive leg the battery temperature gauge was reading 6 bars and it was 77 degrees F outside. At the end of the first drive leg the battery gauge had hit 7 bars but I did pick up a couple of very short charge sessions. At the end of first charging session the session the gauge was reading 9 bars.

At the end of the second drive leg the battery gauge was still reading 9 bars. At the end of the second charging station the battery gauge was reading 11 bars and it was 95 degrees F outside. After the second charging session I drove about 30 miles home, with the air conditioner on, and the battery temperature gauge had dropped to 10 bars.

When I got home it took two and a half hours for the battery temperature gauge to drop from 10 bars to 9 bars. So the answer to my main question was that CHAdeMO charging raised the battery temperature 2 bars. Driving 60 mph did not raise the battery temperature and actually allowed the battery to cool a little bit when the battery got real hot.

I wondered what the relationship was between battery gauge bar readings and charging speed was so a kept track of the charging speed while the battery charged and heated up. At 6 bars the car was charging at 32 kW, at 7 bars it was charging from 29 to 31 kW, at 8 bars it was charging from 25 to 29 kW, at 9 bars it was charging from 18 to 25 kW, at 10 bars it was charging from 14 to 18 kW and at 11 bars it was charging from 14 kW. All of these charges were from eVgo CHAdeMO chargers manufactured by ABB.

So it's obvious that it's fast charging that causes the battery to heat up. Driving doesn't appear to contribute to the battery overheating and actually helps cool the battery when the battery reaches higher temperatures. Right now I'm assuming that 14 kW is the minimum charging speed and that there is enough cooling due to the high battery temperature at this charge rate, even at extreme outdoor temperatures, to keep from having to reduce charge rate even future.

60 mph is an optimal speed if you keep driving a very long distance with a high battery temperature and can only charge at 14 kW. At 60 mph the traction motor consumes about 14kW. If you travel at 60 mph it will take an hour to charge for every hour you drive but if you drive faster than 60 mph, charging will slow you down and if you travel slower than 60 mph, speed will slow you down.

But there may still be advantages to driving even slower. At 45 mpg the traction motor only consumes about 8.2 kW. With a 20%/80% capacity of around 24 kWh on the 40 kWh battery, you only have a range about 100 miles traveling at 60 mph but you will have a range of about 130 miles traveling at 45 mph.

So a 20%/80% drive at 60 mph would last about 1 hour and 40 minutes but a , 20%/80% drive at 45 mph, because the speed is lower and because there is more range, would last about 2 hours and 55 minutes. So, not only is driving at a lower speed not drawing as much current creating less heat in the battery, driving slow is also giving more time for the battery to cool off before the next charge.

So driving at a lower speed and allowing the battery to cool off would allow you to charge at a higher rate. I still want to perform something like a 24 hr continuous driving test and I still want LeafSpy so I can get more accurate information. But I hop that you will find the information I have already gathered useful.

LeftieBiker
Posts: 8779
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 31 May 2013
Location: Upstate New York, US

Re: Using speed to control battery temperature

Tue Jun 05, 2018 3:25 am

Driving doesn't appear to contribute to the battery overheating and actually helps cool the battery when the battery reaches higher temperatures.


This has been clear for quite a while, beginning with the 24kwh pack. In fact, I posited a while back that the accelerated degradation that users of Leaf to Home were experiencing was specifically because the cars weren't being air cooled by driving them while the packs were being drained. Driving can warm the pack, but that requires either a cold pack and hot ambient air, or extremely hard driving combined with warm or hot air temps. The rest of your test is very useful.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

kovadam
Posts: 1
Joined: Wed Jun 06, 2018 12:07 am
Delivery Date: 28 Sep 2018

Re: Using speed to control battery temperature

Wed Jun 06, 2018 12:18 am

Hi!

You can try to run the A/C unit during DCQC, but not cooling the cabin, but turn on maximal heating of the cabin.
I explain why:

Somebody wrote here, that when you turn on the A/C, outside fans will blow. That is correct, big fans will start to "cool" or "heat" the external heat exchanger of the A/C heat pump. This will blow air towards the battery.

However if you turn on A/C with cabin cooling, the heat pump will produce cold liquid on the cabin side of the heat exchanger, and hot liquid on the outside heat exchanger, and the outside fans will try to cool down the heat exchanger, so the heat pump can work with a better efficiency. But unfortunately this air is then "heated" and blown towards the battery, which will cause the battery to heat even more.

But if you turn on cabin heating with maximum capacity, the reverse would happen, the outside heat exchanger will be cold and the inside will be hot, the outside fans would try to heat (warm) up the heat exchanger, and so would blow cold air towards the battery, which might help cool the battery during QC (or at least would prevent a fast and massive heat buildup).

It's just a theory, somebody already experimented with this, but instead of heating he was trying with cooling the cabin, and he managed to raise his battery temperature. Since new Leaf has a heat pump, somebody having a new Leaf should try if it is working heating the cabin to cool the battery.

Another thing I discovered when having a closer look at the bottom covers of the vehicle was the holes on the bottom cover right before the battery. It has some holes which I think actually prevent the air flow to reach the battery, or at least a significant amount cannot reach the battery, air flow is simply lead outside under the car, making a better cooling of the battery while moving impossible. Would be interesting to cover these holes with power tape or something to see if directing more airflow towards the battery can achieve a higher cooldown of the battery while driving.

Regards

kovadam

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