Battery cooling experiment

So I've been toying with a/c ing the garage. Fairly well air sealed and 2 walls+ceiling are conditioned house.

We have been sitting mid 70s in the evening and the garage usually stays about 80. When I connected a single 8 inch duct to the garage, I got the temp down to mid 70s. Not impressive, not cooler than outside. The battery liked it but only by a few degrees. I have the duct pointed under the car. It is a 3 car garage with 14 ft ceilings and 3 west windows (low e).

So I've envisioned a car cooler. A blanket over the car, a box that you drive onto etc.

So for proof of concept, I had some extra 6 inch insulated duct. I cut it into 4 pieces and surrounded the battery on the undercarriage. I opened a little section and shoved my 8 inch duct into that. Ran the a/c and did pretty well

5am - battery 78 degrees. 6:30 - battery 70 degrees (range 67-73 or a little wide). Ambient temp in garage 78. Outside 74. By my calculations, this costs about 2 cents an hour.

I'm leaving town for a few days and that was my impetus for doing this temp test. The car is 75% SOC and I usually get down below 50 when I am leaving town. So I wanted to chill it.

My more stable plan is to use 1x6s in a box configuration of 4ft x6ft and drive onto it every night. I have some solid rectangular duct to connect the box too. This won't seal as well as the current system but it might do pretty well to maintain 60 degrees below the car.

My anticipated cost is $6 a month and I plan to run that for June-Sept or $24 a year. My goal is to drop the average battery temp 10 degrees over the summer which probably takes getting it 15 degrees below ambient garage but given what I got in 1.5 hours, I think that is pretty reasonable.

I have a Seer 16 a/c and pay $.05 off peak which is why my costs are so low. It is a 4 ton unit and I estimate this 8 inch duct is using about 10% of the air flow. It takes 3.5 kw to run at full speed, so 350wh to the car or $.02 an hour. Monthly estimate based on 10 hours of run time (which is way overkill) - I usually prechill overnight for 5 hours.

All EV garage BTW. Will post temps when I get back. I plan to run the a/c overnight some for dehumidification anyway - but yes, I'll run it more than I would have without the car.

With the little knowledge I have, and what I have I contribute to what I've learned from this forum;
is that the most harm done to the longevity of the battery pack is a result of charging while it's hot. Whether it's a hot environment or heat from going to full charge.
So what you're doing here is to prevent the element of heat from breaking down/reducing the longevity of the battery pack right?

Heat kills batteries. The Leaf battery is particularly susceptible. So reducing the average battery temp of the battery seems to be the answer to premature degradation. Charging heats up a battery a lot and heat is the issue - so you can't really separate charging and the heat it generates when it comes to degradation.

All other things being equal, an average battery temp of 70 will last twice as long as an average battery temp of 80 in regards to calendar degradation. Calendar degradation dominates with the Leaf battery.

Thanks for that info.
Good Luck with this!

I tried parking mine on top of a sprinkler where the batteries are located... Maybe this was dumb idea, as I just assumed a well weatherized watertight battery compartment...

Nada movement with the LEAF onboard bars... Now that I have a Spy Pro might see if a sprinkler actually helps. Have to water the lawn sometimes...

But for some reason I don't think to coolness of the water and heat of the battery have a good thermal conduct (and if one is parked on hot fry an egg asphalt, that that is a good thing I suppose)...

JimSouCal said:

But for some reason I don't think to coolness of the water and heat of the battery have a good thermal conduct (and if one is parked on hot fry an egg asphalt, that that is a good thing I suppose)...

Click to expand...

The battery has a fiberous cover under it, so you can't spray the battery directly. http://www.mynissanleaf.com/viewtopic.php?f=38&t=3896" onclick="window.open(this.href);return false;

Not to mention, battery cars are too coarse to tell anything for sure.

If I were to try cooling my Leaf, I'd first try a couple of high-power floor fans directed into the cooling exhaust vents in the rear, followed by air conditioning the garage and then doing the same if that wasn't enough.

I've installed Leaf Batteries in my converted MG. I'm planning to install a a sealed box with blowing Cooled Air. I'm expecting that battery life will be extended with cooled (below 75) Batteries.

gives me the idea that there could be an AGBCU (auxiliary ground based cooling unit)--something incredibly simple such as a water hose attachment with an in and out... At first I was kidding around but then realized it would actually work if properly engineered. Water your lawn and cool your battery...

ahah! Brilliant!

davidcary said: "All other things being equal, an average battery temp of 70 will last twice as long as an average battery temp of 80 in regards to calendar degradation. Calendar degradation dominates with the Leaf battery."

What is your source regarding the above statement? How was it measured, and what was the time frame? :?

derkraut said:

davidcary said: "All other things being equal, an average battery temp of 70 will last twice as long as an average battery temp of 80 in regards to calendar degradation. Calendar degradation dominates with the Leaf battery."

What is your source regarding the above statement? How was it measured, and what was the time frame? :?

Click to expand...

It's 10C/18F difference to double the rate of capacity loss, not 10F.

The formula comes from Arrhenius' equation is is a well established formula to estimate the rate of chemical reactions and the rate of capacity loss of lithium batteries at different temperatures.

Yes, that formula and method is accepted and verified for many chemical reactions. But it is based on a specific activation energy. Different reactions have different activation energies, so different rates of acceleration. For more information, see:
http://antoine.frostburg.edu/chem/senese/101/kinetics/faq/temperature-and-reaction-rate.shtml" onclick="window.open(this.href);return false;

Bob

Would love to see pics, including of how you ran the duct. I always wanted to run a duct to my garage, since my basement is so cold, but worried about fire/smoke hazard.

drees said:

derkraut said:

davidcary said: "All other things being equal, an average battery temp of 70 will last twice as long as an average battery temp of 80 in regards to calendar degradation. Calendar degradation dominates with the Leaf battery."

What is your source regarding the above statement? How was it measured, and what was the time frame? :?

Click to expand...

It's 10C/18F difference to double the rate of capacity loss, not 10F.

The formula comes from Arrhenius' equation is is a well established formula to estimate the rate of chemical reactions and the rate of capacity loss of lithium batteries at different temperatures.

Click to expand...

I do feel a little stupid since I did think it was 10F.

It is possible that I get average temp down 18 but unlikely not that a 50% reduction is mandatory. Now that we have a battery price, everything is easier to quantify. Certainly worth the electricity but maybe not worth the time/effort/supplies. My climate is dead on average so I'm probably able to make it 6 years and I was hoping cooling the battery would get me to 8. Then maybe with the lizard battery, I would get 8 normally and cooling get it to 10.

I already had a duct making a cut through the garage. So my effort is just to get the airflow under the car. Right now is a very temporary setup and I return home today and will check leafspy to see where I am at.

So the battery was at 63. Outside temp 94. Not too shabby...

My "relationship" with this site is pretty much a take only. Thank you...all for being so giving. I have a 2013 SL new less then 1500 miles, it's been in twice for charging issues. This last time they reinstalled the firmware. I swapped out my Boshe power max for a clipper creek level 2 charger. I am charging to 100% now. The service guy said that the car had a charging temp issue. When it reached around 130' it would stop and generate a charging error. I believe this computer issue was at fault but find this post very interesting. I live in south Texas, San Antonio to be precise. I charge in the garage at night. I will get a thermometer to find the actual temp. What should I be aiming for? Should I look into different air flow or circulation methods? Also I usually let the car sit for 1-6 hours before plugging it in. Thanks.

Sounds to me like you have a good thing going. It's a lot easier for you than uprooting everything and moving to Washington state. And your battery will now last as long as mine.

Remember that the battery has a top as well as a bottom. I noticed it was perceptibly warmer inside the car than out, so the interior is trying to shed heat as well. I have started leaving two of the windows down (one on each side). Looks like it helps, but no repeatable measurements yet. But, easy to do.

gbarry42 said:

Remember that the battery has a top as well as a bottom. I noticed it was perceptibly warmer inside the car than out, so the interior is trying to shed heat as well. I have started leaving two of the windows down (one on each side). Looks like it helps, but no repeatable measurements yet. But, easy to do.

Click to expand...

Great Tip

foolios said:

gbarry42 said:

Remember that the battery has a top as well as a bottom. I noticed it was perceptibly warmer inside the car than out, so the interior is trying to shed heat as well. I have started leaving two of the windows down (one on each side). Looks like it helps, but no repeatable measurements yet. But, easy to do.

Click to expand...

Great Tip

Click to expand...

I try to leave the windows open while my 2011 LEAF is parked in the garage. The traction battery cools at about 0.5F/hr overnight, but I cannot distinguish a difference in cooling rate with or without the windows open. However, I notice that it is a bit warmer in the LEAF if the windows are closed.