Drive at night to control battery temperature

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TexasLeaf

Well-known member
Joined
Mar 21, 2018
Messages
115
Location
Texas
I have read and heard of many people commenting about charging in the shade to control battery temperature and reduce slow charging issues on the 2018 Leaf. I thought to myself, charging in the shade doesn't make any sense because the battery pack is underneath the car and can't get directly heated up by the sun. Then I realized that what people were talking about was charging while your car was sitting right on top of pavement that had been heated by the sun.

The pavement heated by the sun can be 20 degrees F or more hotter than the air temperature. So the air coming right off the pavement to cool the battery pack while charging a Leaf in the shade is a lot cooler than air coming off a non-shade charging area. Good advice, but how do you make use of this advice when there are so few fast charging stations in shady spots?

Simple, travel at night when it's shady everywhere. It's typically 25 degrees F at night cooler than in the heat of the day so, not only is there no heat coming off the pavement at the charging spots and on the highway, the surrounding air temperature is lower at night. The air cooling the battery pack could be 50 degrees or more cooler at night than in the heat of the day.

So to take advantages of nighttime battery pack cooling on very long trips with multiple fast charging stops you should plan your trip so that you do most of your charging late at night after the pavement cools off and in the early morning before the sun has a chance to heat things up. Other temperature controlling techniques in conjunction with nighttime driving, such as driving for range not speed, should further reduce battery pack heating and slow charging issues. I have not had much opportunity to test the nighttime driving to control battery temperature theory but the theory appears sound.

If have any experience travelling long distances with multiple fast charges at night please share your experience related to how nighttime charging speeds compare to daytime charging speeds.
 
I'm finding that using a cooled garage is very effective, even when you drive in the daytime, because the pack is cool to start with. That wouldn't apply as much to multiple fast charges on hot days, though.
 
TexasLeaf said:
If have any experience travelling long distances with multiple fast charges at night please share your experience related to how nighttime charging speeds compare to daytime charging speeds.

Do clouds count? I've taken a long trip in both the USA and Canada with a 2014 Leaf in winter. That locally means clouds and temperatures near 40F/5C. Liquid cooling from the sky. A wet EV, as usual. I planned the trip to be mostly 100 km/h, or 55 MPH or 60 MPH.

Battery temperature at the start of every charge session was 5 bars or less. 27C or 81F.

Is 20C over ambient about what you see with the 2018?
 
WetEV said:
Is 20C over ambient about what you see with the 2018?

When driving at 100 kph (60 mph) my 2018 pack seems to spend most of it's time around 30C (86F). This holds true for ambient temperatures from 10C (50F) to nearly 30C (86F). At or above 30C (86F) I'm seeing around 35C (95F) in the pack. Below 10C (50F) ambient I usually see about 20C (68F) pack temperature. I don't have access to L3 charging so these are all starting with a relatively cool pack about 2-3C above ambient.
 
I’ve been meaning to ask about this. Do people just use Leaf Spy to see their battery temperature? The temperature gauge is awful. Does anyone know what it means? I’ve rarely seen it go above half, but we’ve been having a freak heatwave recently and it’s been one notch above the middle almost every day. Any idea what that means?
 
jonathanfields4ever said:
I’ve been meaning to ask about this. Do people just use Leaf Spy to see their battery temperature? The temperature gauge is awful. Does anyone know what it means? I’ve rarely seen it go above half, but we’ve been having a freak heatwave recently and it’s been one notch above the middle almost every day. Any idea what that means?

Supposedly it's the same number of bars, but with no more borders to let us count them. So I read it in approximate % increments like 40%, 50%, 55%, etc. As for how hot is Hot, I've been keeping my car in a cooled garage during the heatwaves, and it stays at roughly 30-40%. The hottest I've seen was one 29 minute QC on a warm night in which it got to about 60%.
 
jonathanfields4ever said:
I’ve been meaning to ask about this. Do people just use Leaf Spy to see their battery temperature? The temperature gauge is awful. Does anyone know what it means? I’ve rarely seen it go above half, but we’ve been having a freak heatwave recently and it’s been one notch above the middle almost every day. Any idea what that means?

Yes, one of the reasons to own Leafspy is battery temperature display.

Suggestion to Nissan (and GM/Ford/Honda/Toyota/...), put in a real temperature readout.
 
LeftieBiker said:
jonathanfields4ever said:
I’ve been meaning to ask about this. Do people just use Leaf Spy to see their battery temperature? The temperature gauge is awful. Does anyone know what it means? I’ve rarely seen it go above half, but we’ve been having a freak heatwave recently and it’s been one notch above the middle almost every day. Any idea what that means?

Supposedly it's the same number of bars, but with no more borders to let us count them. So I read it in approximate % increments like 40%, 50%, 55%, etc. As for how hot is Hot, I've been keeping my car in a cooled garage during the heatwaves, and it stays at roughly 30-40%. The hottest I've seen was one 29 minute QC on a warm night in which it got to about 60%.
As an FYI, the old pre-'18 temp gauge was crap. It had huge overlapping ranges: http://www.electricvehiclewiki.com/Battery#Battery_Temperature_Gauge. I can't speak to the behavior and ranges for the '18. And yes, use Leaf Spy to read the actual pack temp sensor values.
 
Charging speeds start to get limited at about 90 degrees F, which is about seven bars on the battery temperature gauge. Anything above 7 bars and you should expect slower charging speeds. If you’re fast charging starting starting at 7 bars, the gauge will jump up to 9 bars.
 
I understand the motivation, but thread titles like this are what makes normies scoff at the idea of electric cars.
 
Agreed! Why would anyone buy from an EV manufacturer who makes you go through such shenanigans! It is beyond silly and simply unacceptable today!

Nubo said:
I understand the motivation, but thread titles like this are what makes normies scoff at the idea of electric cars.
 
Nubo said:
I understand the motivation, but thread titles like this are what makes normies scoff at the idea of electric cars.

There is a lot of very negative press on the 2018 Leaf because of the battery overheating issue but there is very little dedicated to understanding the issue or how to manage battery temperature. Forums like this are intended to help people with the issues they have with their vehicles. This thread not only offers Leaf owners and prospective owners one technique to manage battery temperature but identifies that the issue doesn’t have to be as bad as indicated in press.
 
TomT said:
Agreed! Why would anyone buy from an EV manufacturer who makes you go through such shenanigans! It is beyond silly and simply unacceptable today!

Makes you? How so? Unless you road trip in the car often in the heat, you don't care. The Leaf is a lower cost around town and commuting BEV. Use it that way, and you will likely love the car. If you want a frequent road trip car for trips beyond one QC, buy something else.

Hammers make horrid screwdrivers.
 
TexasLeaf said:
Nubo said:
I understand the motivation, but thread titles like this are what makes normies scoff at the idea of electric cars.

There is a lot of very negative press on the 2018 Leaf because of the battery overheating issue but there is very little dedicated to understanding the issue or how to manage battery temperature. Forums like this are intended to help people with the issues they have with their vehicles. This thread not only offers Leaf owners and prospective owners one technique to manage battery temperature but identifies that the issue doesn’t have to be as bad as indicated in press.

I didn't mean to suggest the thread shouldn't exist or even that it's unhelpful. I'm just saying that in larger terms it's unfortunate that 8 years into LEAF production we're still talking about austere methods of coping with battery deficiencies.
 
Some actual experience:
My Leaf is kept essentially every night in a detached garage. It has been a predictably hot summer in Houston, TX (90 -95 degree afternoons - 100's today :twisted: ). Most charging is done overnight, with 3.3 kw power and 80% limit. LeafSpy temps in the morning are in the high 80's to low 90's. The garage floor temp is around 88 degrees (IR gun). Driveway temps in afternoon sun (concrete) are 125 degrees+.

I park in a garage at work and the usual temps when I get back home are in the mid to high 90's. Never hit 100 yet. I put about 6000 miles per year on the car and use it almost every day. This "cycle" has been documented for a couple of weeks now. I'm interested in what happens this winter - will keep taking the readings.

The surprise to me is that the heat capacitance (in my situation) seems to keep the battery at fairly constant temps - and it seems to cool fairly well at night even with LII charging. I'd bet that some QC's and/or parking in full sun (on black tar) would fairly rapidly elevate these temperature ranges. The temp bars have stayed at 6 - never moved since start of summer.
 
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