Active cooling your leaf battery

[GetOffYourGas]

I am SO glad that I don't have to concern myself with such considerations anymore! Now I just charge and drive without worrying about it.

Me too. I've never had to worry about my battery getting this hot. The worst I've had to do is to delay charging until overnight. I feel for you guys in hot climates.

This thread has been very interesting to me nonetheless. One of my pending projects is to upgrade the cooling on my CMax Energi's battery. Ford basically circulates cabin air around the battery via some bulky duct work. I am looking for ways to reduce the bulk (and thus increase my trunk space) while maintaining or improving cooling performance.

[Rashi]

I just wrote a reply for all the post for nearly an hour and when I try to preview it just disappeared

[Evoforce]

Yep, It happened to me too! Grrrrr......

[Rashi]

Summary of the lost reply. Thanks for all the comments. Great WIP Rob will keep an eye on your project.

according to my calculation when charging using 40 kW FC heat out put will be = 768 W (P = I^2 x R) (R from NREL document,2011 Nissan Leaf – VIN 0356 Adv anced Vehicle Testing – Beginning-of-Test Battery Testing Results)
https://www.dropbox.com/s/de4pveli1p783 ... e.JPG?dl=0

according to EERE (Thermal Management Requirements for EV) the thermal output is nearly 2 kW. So I'm not sure which is correct.
https://www.dropbox.com/s/vjszrcwj1kpzx ... 0.JPG?dl=0

Pelteier has about 60% efficiency that mean around 1.6 kW would have to be spent on cooling.

12v compressor is a interesting idea I'm trying to get a mini fridge for testing.

Temperature gradient within the battery pack have to be minimized.
https://www.dropbox.com/s/nkowo89ydamez ... p.JPG?dl=0

Didn't knew about Fluorinert before thanks for that information also.

Sad that Nissan did not try to use a simple cooling solution like in KIA. With proper sealed ducting and filtering it would work. But I'm afraid to mess with battery casing.

We don't have battery warranty from our local Nissan agent that's why all this struggle!

[Rashi]

Thought of starting simple for the battery cooling.
I found that there's two sheet metal bracket that used to hold the battery at the rear. Thinking of adding a 12 cm motor cycle cooling fan to create an airflow from front of the vehicle.
Problem is there's a narrow channel that the air can be sucked from the front.
That will be the passage that should be used if cool air is introduced from another source(peltier/air con).
I'm afraid to remove the entry between the chassis and the service plug because of safety reasons.
This is not effective as liquid cooling, but hey something is better than nothing!



Checked if there's space for 12 cm fan. There's little bit of obstruction from the handbrake lines.


Planning to get a sheet metal fabricated for the fan bracket also ordered a 12 cm delta fan.


Also found a hole where I can route wires to the rear boot space to add a external battery or a power supply to power the fan.


What do you guys think?

[Leafabout]

This will be the first summer I have had my Leaf. I will have to park it on the hot pavement in front of my home where there is no shade and I am concerned about the heat/battery issue. Would it do any good to take a water hose and water down both the pavement under the car and the bottom of the car where the battery pack is located?

[miscrms]

I could be wrong, but I suspect that airflow over the top of the battery case will do very little. None of the cells are in physical contact with the top case IIRC, and there is a gasket seal between the top and bottom case that will reduce the thermal path between the two. Even then only a small number of cells have a decent thermal path to the bottom case.

[GetOffYourGas]

This will be the first summer I have had my Leaf. I will have to park it on the hot pavement in front of my home where there is no shade and I am concerned about the heat/battery issue. Would it do any good to take a water hose and water down both the pavement under the car and the bottom of the car where the battery pack is located?

It certainly wouldn't hurt to hose down the pavement. That's a quick and effective way to reduce the amount of heat radiating on the bottom of your car.

BTW, not knowing your location, it's hard to know exactly how hot that pavement will get in the summer sun. Around here, it's hot but one can still typically walk on it in bare feet in all but a few days of the year. I wouldn't try that in Arizona though

[Kramy]

I have experience with mineral oil as a coolant, 0 issues with corrosion, 0 electrical issues overall it just works. Only issue is that the oil wicks through any multi strand cables that penetrate the oil/ air layer.

I don't know how much empty volume is in the pack, but density is around 7.5 lbs/ gallon.

Price for medical grad mineral oil is about $15/ gallon.

One thought would be a sump and a dribble over all of the batteries when returned from the radiator. I'm going to guess that a few gallons would be adequate.

Did anyone try the mineral oil cooling? Pure mineral oil is non-conductive, and transfers heat about 5x more efficiently than air. If you had the battery packs surrounded with the stuff, it would provide a large semi effective heatsink, keeping temperatures closer to ambient longer. If your trips are short and you park in the shade, that might be enough in many climates to provide significant improvements to battery longevity. If it takes 30 minutes longer for the battery to go from 40C to 65C, that makes a big difference to degradation speeds.

Lack of airflow is killer to electronics. I've seen embedded SoCs run at 80-90C. If you have a fan blowing air across them they'll drop to 60-70C. If you heatsink them and blow air across the heatsink fins, 40-50C.

[RNM]

Mineral oil is a good idea except that it would need 100~200 liters, since there's so much free space inside the pack