Long Distance Travel Battery Thermal Concerns

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JoeS

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As we drive, the battery temperature increases.
When we slow charge, the battery temperature increases.
When we Quick Charge, the battery temperature really increases.

Thus, as we travel long distances, stopping only to charge the batteries, the battery temperature does nothing but increase continuously.

When I took my Christmas Day 200-mile trip last year, the battery temperature was IIRC over 30degC (86degF) on the final climb into the Sierra foothills, despite the ambient temperature at zero degC (32degF). :eek:

From a different thread,
Malm said:
rkarl89203 said:
…246 miles!… Yowza!…I love my Imiev!
Have you any idea what where the temperatures in the battery in the end? The i-MiEV wasn´t made to do such long trips. Yes we can do it, but we will pay a price, specially if we drive it fast, in long trips, without letting the battery temperatures going back down. When you drive they are getting hot, when you are charging they are getting hot, so if we are using it, day by day, without letting the temperatures going down, we will loss more then 10% in an year. But yes, some of us have some solutions to that, and we can even make temperatures going down when driving, with the cold air of the air conditioner going to the battery, losing something like 10% in range (that´s my choice in this summer days, don´t want to see more then 30º C in my battery no more - OK, they can be there, but not for several hours).
I have been mulling this issue ever since I took my first long-distance CHAdeMO trip last Christmas. The i-MiEV does not have a battery temperature readout, and thus the only way to get that temperature is with CaniOn (and OVMS?).

This may be the most significant reason that may keep us from making long-distance trips with the i-MiEV. Does anyone have any long-distance CaniOn readings they can share?

The good news is that the motor, controller, and charger are liquid-cooled, with a nice radiator out front.
 
I did 81 miles with Bear today, mostly highway with two hours of level 2, and my cells were between 30 and 34 C with temp sensor #64 at 36 C. Outside temperature was 75-80 F with near 100% humidity.

Having AC blow into the pack is the only way to cool it unless outside air is below 70 F. During my trip to Morgantown, my battery was 35 C and up (~95 F+), and wouldn't cool down with 80 F ambient air blowing in at max speed during a level 2 charge.
 
"Does anyone have any long-distance CaniOn readings they can share?"

If they are taken in a day of 30º C outside, they will be between 40º C to 50º C, for sure. And at this temperatures, degradation goes what? Three times faster then at 25º C? That wouldn't surprise me.
 
I have been excited about going on a Road Trip
ever since they installed a Fast Charger Corridor
from Montreal to Quebec city,

This weekend I made it happen.

In brief review
The temperature at departure 7C (45 F)
mid day 23C (73 F)
That night on return 15C (59 F)

625 km (388 miles) total - edited after re confirming trip meter
Departure at 6:30 am return at 9:30 pm

9 Fast Charging sessions in 15 hours
2 short sessions and 2 sessions to 90%

mostly charge & run
1/2 hour lunch down time
1 hour down time in Quebec City

This was probably pretty hard on the battery.
Bluey performed flawlessly

I wish I had the knowledge and equipment to
share the battery temperature statistics with all of you here

I'll start another post with more detailed
at a later time.
 
Wow. What a distance for one day!

Did you notice the AC running when quick charging? I'm sure the fans were running, but if the battery temperature gets above 30 C I believe, the AC will turn on. Correct me if I'm wrong. I figure this would be the easiest way to estimate battery temperature.
 
On my 246 mile one day trip to Milwaukee and Madison during QC in Madison the AC came on to cool the battery big time.

If battery temps cause such degradation, why are we not hearing more stories about it?
I am planning a 3000 mile trip so I am curious.
 
rkarl89203 said:
As for the battery temp, that is not a problem here in the upper Midwest.
It looks like you're rethinking this??

Continuous driving interspersed with QC sessions can cause battery temperature problems even if the outside temps are quite cold. The battery heats up when you charge it and then it heats even more when you're driving the car, especially if you're driving at high speeds

You can do it, but there's no question it will take a toll on the battery

Don
 
The CMU temperature has to reach a high temp limit of 60 C before it throws a trouble code.

With an eight or ten year warranty why worry--just drive the hell out of it and see if you can wear it out or cause it to fail. The factory obviously has a high level of confidence in their systems to put such an awesome warranty on the pack. These are just cars that are made to be driven, not parked in an air conditioned garage (really?).

It's your duty as the consumer to drive it as fast and far as you can, charge it as much as necessary to reach your destination, and get the greatest and best use of the product as you consume the battery energy. Rinse and repeat.
 
Checked up on my trip meter this morning with a clear head and made a correction on the distance traveled. Sorry I was a little road buzzed,
The correct distance traveled was 625 km (388 Miles)

On the second to last Fast charge We charged up to 90% and were on the highway traveling 85-95 kmph, (55 -60 mph) for a distance of 70 km (43.5 miles)
I guess the battery was pretty warm since when i started the Fast charging the ac kicked in immediately and the fans were running for most of the charging session.
 
kiev said:
With an eight or ten year warranty why worry--just drive the hell out of it and see if you can wear it out or cause it to fail. The factory obviously has a high level of confidence in their systems to put such an awesome warranty on the pack.
My worry would be . . . . that it doesn't 'fail' but I wind up with only 50 or 60% battery capacity left when the warranty ends. Malm has some pretty scary statistics on capacity loss and he believes much of it is due to higher battery temps. The warranty doesn't cover capacity loss - So long as it recharges to 16 bars, the battery is 'good' so far as the warranty goes, even if those 16 bars are now only 50% of their original capacity

Don
 
So...even though we have the best battery warranty and the least expensive car to operate we shouldn't use it?
If so, what's the point of owning an EV?
I didn't buy my i-Miev to look at it in my driveway.
 
Use it, but like anything else, take good care of it so it will last.

You wouldn't drive a gas car 50,000 miles without ever changing/checking the oil, would you? Why abuse the battery and hope it fails?

This morning, I had cool air (just vents as it was 65 F this morning) flowing through the pack to try to cool it from 82 F. I'll probably push AC through it on the way home.
 
This is another reason I like the pusher trailer. With the pusher engine set to 'charge sustaining mode', which matches power to the load of cruising at 65 mph on flat highway, a long trip can be accomplished without a single fast-charging session, reducing that stress on the battery. EVen with the repeated high-amp regen and discharge employed when pushing up and down highway hills, the battery doesn't warm as much as it does during continuous discharge on the highway plus DC fast charges.
HowEVer, the battery heating and cycling issue is another reason to add remote throttle control to my pusher, so I can coast downhill rather than having to regen hard to scrub off speed when pushing downhill, and push harder when going uphill. This finer level of control should improve both fuel economy and Wh/mile as well as reducing the effective number of cycles that the battery sees.
 
JoeS said:
As we drive, the battery temperature increases.
When we slow charge, the battery temperature increases.
When we Quick Charge, the battery temperature really increases.
My recent Canion readings suggest that driving can increase the battery temperature more than DC Quick Charging.

I took a trip yesterday, Father's Day, and was able to use a new DC Quick Charger located at a Nissan dealer that now gives me easy access to Philadelphia. Here's a summary of the battery temperature:

Drove 31 miles mostly 50-55mph with AC on: Battery temperature increased 6.48ºF (87.26ºF to 93.74ºF)
DC Quick Charged 10 minutes (gained 30% charge): Battery temperature increased 1.44ºF (93.74ºF to 95.18ºF)
Drove 29 miles mostly 50-55mph with AC on: Battery temperature increased 4.32ºF (95.18ºF to 99.50ºF)

Driving was responsible for the majority of the temperature increase.

To cool, our batteries must transfer their heat to the surrounding air in the battery pack. Heat transfer from a solid (our batteries) to air is directly related to the surface area of our batteries (LEV50-8's and LEV50-4's). Since our batteries are a solid mass and do not have a heat sink, there will only be a limited amount of heat transfer to the surrounding air in the battery pack no matter how much cold air we blow through the pack. By blowing cold air through the pack, we cool the 66 external temperature sensors more than we cool the actual batteries. With minimal surface area, our batteries require significant time to transfer their heat to the surrounding air. Battery temperature increase is directly related to the current flowing through the battery squared times the resistance of the battery times the time the current is flowing through the battery (I*I*R*t). Driving, I averaged around 40 amps for 40 minutes each way, while DC Quick Charging I averaged around 60 amps for 10 minutes. The Canion battery temperature readings support this hypothesis.

By DC Quick Charging (which I seldom need to do) we gain the ability to drive continuously and not let our batteries cool down. Any detrimental effect high temperature would have on our batteries is related to the number of hours our batteries discharge or charge at the higher temperatures. So we need to compare infrequent long drives using DC Quick Charging at higher battery temperatures (in my case two hours) to frequent short drives at lower battery temperatures (in my case hundreds of hours).

Here is the only data we have relating battery discharge capacity retention and temperature:
bmxoVSm.png

The graph compares charging and discharging at two constant temperatures 25ºC (77ºF) and 45ºC (113ºF). Most of my battery's life charging and discharging has been in the 77ºF range (lower in the winter), and I doubt my battery has never been at 113ºF.

In short, the limited data we have suggests that the temperature effects on our battery's capacity by occasionally taking a longer trip using DC Quick Charging are minimal.
 
While I can agree with that, how much effect is had by the AC blowing cold air into the pack while quick charging?

While amperage plays a role in how much the cells warm, I think active time (charging or discharging) plays a major role. For example, my battery gets much warmer on a longer but slower level 1 charge than it does on level 2. Combine 7 hours of level 1 with 45 miles each way of driving around it, my battery has increased from 81 F to 97 F, with air 65 F and lower blowing into the pack for all driving time of 3 hours. When I got home, I just let Max AC flow full force into the pack to try to cool it. I doubt the pack would've hit 90 F with two hours of level 2 instead of 7 hours of level 1.

This is where I think the Volt and Tesla vehicles have it right with a liquid cooled pack. It's much easier and more effective to dump heat into a liquid than air.
 
Well, I am going to drive as I do...daily to work and back, less than 20 miles, 5 days a week.
On the weekends the occasional 100+ mile trips.
I have had the car for a 15 months, and only DCQC on longer trips where there is the occasional quick charger.
I have quick charged only 6 times in 15 months. I don't think that is excessive.
I have had all the recalls done, my one-year mark annual check showed NO degradation.
I religiously do checks on the car that aren't even required.
The suggestion I am 'driving the car hard so the batteries fail ' is absurd.
This car is reliable, peppy, and FUN.
Remember fun? I hypermile, go for maximum regenerative braking, and take care of this damn reliable car.
Enough said.
 
I believe I'm the one to blame about this discussion. But one very interesting discussion. If we let the battery, for one day, reach the 40/50 ºC, the effect will be so small, that it should not worry us. The problem is if they are always, day by day, at that values. If they are an entire month at that values, then there is a problem. And I think, in summer (real summers like the ones in Portugal, where 35 ºC outside happens sometimes), if we are driving the car for 200 km all days, and have to charge it twice a day, they will be, at least, clearly above 30 ºC. Before buying one, we should know this things and see if the use that we will make of it will subject the cars to this conditions frequently.

I believe cold air going inside battery pack is very effective. I do it since may of 2014. Someone said here that the sensors are being colder, but the cells not so much. I agree partially. I see some recovery of temperatures in the end of turning off the air conditioner, but will be significantly less hot then they where before receiving the cold air. On the first three years, without the procedure of cooling the batteries, I saw a significant loss of capacity. I believe that the last year I have reduced the rate of degradation by half (or even more). And I see the effect of the cold air for several hours.

So, my experience tells me that cooling the batteries with the air conditioner is effective and I will do it every time that my batteries are getting over 25ºC and I don't need 10% extra energy to reach the next charger. Doing it for the last 14 months and happy with the results, because in the last 14 months, for my perception, the rate of degradation went down significantly (at least, if in the past, my turtle simply vanished, now is there with 9,5% usable SoC in this 14 months, and I don´t see a loss of range in these last 14 months).
 
"This is where I think the Volt and Tesla vehicles have it right with a liquid cooled pack. It's much easier and more effective to dump heat into a liquid than air."

I love to be me to decide when is the time to cool the pack (if we have extra energy, sometimes for free, why not use it to cold the battery, even if they are at 27ºC?). And we can do it now with the i-MiEV with the help of Canion. I believe this is not possible to do with any other EV.
 
So, Malm and PV1, are you simply using the car's aircon or have you each modified that ducting flap to force cold air into the battery pack? Recall, there is no such battery cooling ducting for i-MiEV's without CHAdeMO.

Dumb question: is there an i-MiEV configuration with no CHAdeMO but which has battery heating/cooling package?

BTW, it was my intention when I started this thread to discuss concerns about using the i-MiEV for continuous long-distance travel and not the occasional CHAdeMO quick-charge zap.
 
I unplugged the servo controlling the damper, loosened the screws, and flipped the damper manually. Now, anytime I direct air to the floor, it automatically goes to the battery. I never use the floor vents unless it's really cold out. If outside air is cooler than the battery, I simply run the fan on high, but if I need AC for the cabin, then I'll share it with the battery...at least on these 85-90 F days.

Yes, the 2012 i-MiEVs that have the cold-weather package include battery warmer (the ductwork and servo) and heated mirrors. This was available on both the ES and SE (quick charge port was part of the premium SE, but cold weather was its own package).

I agree that the i-MiEV is easy to manually cool/heat the pack, but we do have to watch the temps more closely than a liquid cooled pack, though it evidently will engage battery cooling at some point. I believe the Volt normally only cools the pack when charging (account from the driver of the company Volt).

Yes, this thread should only concern longer travel. The thing is that most of us only have data on trips less than 150 miles. I'm starting to agree with Jray3 in that the least-stressful way to travel long distance is with an external motive force. The i-MiEV really wasn't designed for travelling more than 100 miles a day.
 
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