Active cooling your leaf battery

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RNM said:
Mineral oil is a good idea except that it would need 100~200 liters, since there's so much free space inside the pack
Err - are you sure about that? If true, yowsa, that's a lot!
https://chargedevs.com/wp-content/uploads/2015/12/NIssan-Leaf-Battery-Pack.jpg

I saw on a mineral oil cooled PC site that STEOil makes "tech-ready" (Electronics safe) mineral oil, and sell it in rather large quantities.

"Crystal Plus Tech Grade Mineral Oil 70T - 5 gal"
http://store.steoil.com/
http://www.steoil.com/msds-tech-data
http://store.steoil.com/categories/Crystal-Plus-Tech-Grade/CP70T/?sort=featured

I was hoping one or two would do the trick. If it'd really take 10 of those, then ouch - that's nearly $1000 in mineral oil!

I see they offer it by the 55 gallon drum, though, and you have to call in for a quote. I just did, but it still came in over $500 before shipping. :lol: I have a feeling that if anywhere near 200 litres is required, it's going to make more sense to just save up for a new battery pack. (They'll drop in price within a few years, once Tesla is mass producing lithium ion batteries.)

Does anyone know how well the battery packs are sealed? It appears that if filling it up fully, a lot of oil would be in touch with the seal, and be located above it. Just wondering whether this idea would turn into a huge mess.

And to fill it up, the cover itself would have to be modded to include a sealable opening on top?
 
FYI , electrical transformers have been filled with oil , for decades . I am sure it aids in cooling .

http://www.geindustrial.com/products/transformers/liquid-filled

Weight is probably not an issue with stationary transformers .

However , the added weight for an EV would be a consideration .

God bless
Wyr
 
WyrTwister said:
FYI , electrical transformers have been filled with oil , for decades . I am sure it aids in cooling .

http://www.geindustrial.com/products/transformers/liquid-filled
Awesome! Sounds like it's an idea on the right track. :D

WyrTwister said:
Weight is probably not an issue with stationary transformers .

However , the added weight for an EV would be a consideration .

God bless
Wyr
Apparently 1 litre of mineral oil is somewhere around 2 pounds? Not sure exactly how much is required, but it probably would be like having another person or two in the vehicle.

Edit:
Mineral oil varies in specific gravity from 0.818 to about 0.920, depending on how refined it is.
So one US gallon weighs between 6.83Lbs to 7.68 Lbs...
From the midpoint:
5 gallons = ~19 litres.
19 litres = ~36.25 lbs.
100 litres = ~190.8 lbs.
 
RNM said:
Mineral oil is a good idea except that it would need 100~200 liters, since there's so much free space inside the pack

My theory would be to have it dribble over each cell with a few gallons at the bottom.

For whatever reason I never get notified of anything on this forum.
 
Or maybe some sort of rotating sprayer network (think lawn sprinkler) that would get some on each cell.
Probably easier to get a 1/4" or so piece of vinyl tube to the top of each cell. Pump in bottom of battery pack that heads to heat exchanger in the grill, then back in to the pack and distributed via above mentioned tubes.
Just a thought to keep system weight down in the 25 lb range.
 
Active systems are more prone to failure, and possibly too energy intense depending on the flow required. The most obvious solution is to redesign the battery compartment to contain less airspace, then fill it to the brim, but I'm not an expert on moulding plastic, so that's not currently one that I could tackle.

I'm curious how much weight you would add by filling up the stock container completely?

-Kramy
 
Adding a reasonable solution (as an engineer):
make one (or two) holes (IP68).
Insert tubes (air in and air out).
Connect hose "air in" to climate control air output side (after temperature treatment) to "center vent" channel.
Hose must be pretty big, diameter at least 25mm (1").
Inside the battery divide "air in" in two (left and right side, vehicle front). Best to divide both sides in two: up and down.
So all together 4 air in holes.
In the back of the pack (behind the bigger stack) two hoses left and right connect together and
make one "air out" hose, same diameter. Add "one way valve". Air out must be purged inside
the vehicle, best near trunk air out vents.


Worst that can happen is that if vehicle will get in a flooded region (40+cm), it might ruin the battery (like iMiev).
But that is not really a reason, both ways vehicle will be scrapped.
Condensation should not be a problem, AC air is dry.

Air can be pushed harder if center vents closed/half closed.
Air will be heated in winter (not needed for hot regions, but also not bad).
 
I maintained electrical switch gear from the industrial revolution (built just prior to WWI) when I was head of maintenance for a number of woodworking plants in New England and those used PolyChlorinatedBiPhenols in a bath. Inside the bath there would be no insulated wires just bare metal bus bars so filling a case full of plastic parts, insulated wires, etc along with batteries that swell and burst when they fail may not be the best idea in the world. Imagine servicing a formerly 400 lb battery case full of oil contaminated with the lithium compound from the batteries that now weighs closer to 600 lbs or dealing with a fire from a lithium polymer battery soaked in oil.

The batteries in the Leaf are also like Gremlins in that you can have catastrophic failure if you get them wet so making more openings under the chassis to allow greater air flow would also increase the potential for water intrusion into the battery case causing a premature failure.

I was reading a warning that these cars needed to have the carpets and upholstery vacuumed more often than those with internal combustion engines, especially if you have pets that you transport, since cabin air vents through the battery case to cool it in the summer when the AC is running leading to the potential for the battery cooling vents from the cabin to get restricted or clogged by pet hair/dander if the car is not kept well cleaned. I have not confirmed the accuracy of this but that is what one "Leaf Expert" advised.
 
Nonsense. Leaf battery is not in any way connected with cabin carpets.
iMiEV has AC air cooled pack. Nothing happens with those vehicles (except Katrina Hurricane etc).
 
any one considered helium?,approx. the same thermal conductivity as mineral oil,very safe inert gas,used as a fire retardant and purge gas and cheap,small weight saving,i presume the battery pack has a vent somewhere which would need a work around.
 
Nissan could put a hose connection on the car. Arriving home with a hot battery, attach the garden hose and turn on the water to cool the battery. We have 55 deg. well water that would cool the battery down. Sorry for the strange idea...
 
Marty said:
Nissan could put a hose connection on the car. Arriving home with a hot battery, attach the garden hose and turn on the water to cool the battery. We have 55 deg. well water that would cool the battery down. Sorry for the strange idea...

It might be worth trying this: spray the rear underside of the car with cold water for 5 minutes or so when the pack temp is high, and see if it drops noticeably. I'm considering trying a portable air conditioner blowing through the cooling tunnel if the new car won't fit in my garage.
 
^^^ I''m guessing the bottom will be all plastic(or a plastic shroud like on my '13) so spraying water wouldn't really help as the plastic shroud would be a pretty good thermal insulator :(
Your portable A/C unit would be a better choice if you could get the cool air to blow through the battery, might be kind of a hassle and wouldn't really help on the road, but would be an option.
Too bad Nissan doesn't have a fan that blows air through the battery when charging(at least QC'ing) like on at least one other EV they sell.....as TomT is fond of saying, we don't need no stinkin' TMS on our Leafs :?
 
jjeff said:
^^^ I''m guessing the bottom will be all plastic(or a plastic shroud like on my '13) so spraying water wouldn't really help as the plastic shroud would be a pretty good thermal insulator :(
Your portable A/C unit would be a better choice if you could get the cool air to blow through the battery, might be kind of a hassle and wouldn't really help on the road, but would be an option.
Too bad Nissan doesn't have a fan that blows air through the battery when charging(at least QC'ing) like on at least one other EV they sell.....as TomT is fond of saying, we don't need no stinkin' TMS on our Leafs :?

I should have been more specific. There is (was?) an opening in the rear diffuser that one could use to spray water or air into the cooling channel. Can someone tell us if it is still there?
 
Rashi said:
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/de4pveli1p783nk/resistance.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/vjszrcwj1kpzx0k/ev%20100.JPG?dl=0

Peltier has about 60% efficiency

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!

That’s useful info thanks. The 2kw vs .768kw figure difference could be due to amps at full acceleration being much greater than amps at quick charge.

I’ve tried using Peltier cells to cool smaller lithium batteries. Using heat conductive pads for intimate contact, they were reasonably successful keeping at least the surface of the battery a few degrees cooler than ambient, but it wasn’t clear whether the temperature gradient between the battery surface and the battery internal was within acceptable limits that would help limit battery degradation. This could be why Tesla’s cooling system works so well — they run fluid around many small cells.

Last week I saw an online classified ad for a used 2013 Leaf in Malaysia; 83% SOC at 3 bar dash readout & 53km guess-o-meter range, asking price about USD15k. A new 24kwh battery here costs about USD17k including labour. Local Nissan dealer staff verbally said they need the old battery back, and will re-use the existing weatherproof casing. This sort of prevents further off-vehicle cooling experiments on the old battery pack, if we choose to get a new battery.

The 2013 Leaf battery warranty here is 3 years or 100k km; less generous than in the US.
 
I have an MS in Physics and PhD in Materials Engineering. Parking over a puddle won't work because the water is cooling but not the air above it. However, you don't have to drill holes in the battery pack as long as you have a heat conducting path like metal, plastic or even an air pocket. Still air is a good insulator but above about a half inch gap air conducts heat by convection. That's how triple pane windows work. You can't just make a double pane window as thick as a triple pane and expect the same result.

Here's an idea - place water in a pan, put a jack in the water, and raise it until it touches your battery - it just needs to touch, you don't have to jack up the car. I'm looking to buy a leaf but when I do I'll have to get a leafspy and see how effective this is.

I live in Phoenix, AZ where 100+ temperatures are common so I'm investigating this issue.

Sincerely Yours,

Jim Sizemore
 
hoppingbuffalo said:
Here's an idea - place water in a pan, put a jack in the water, and raise it until it touches your battery - it just needs to touch, you don't have to jack up the car. I'm looking to buy a leaf but when I do I'll have to get a leafspy and see how effective this is.

Interesting, setting up a heat sink / heat spreader. Unfortunately I don't think the battery area is directly exposed to the ground. Maybe a heat pipe solution?
 
I think that most people are underestimating the amount of cooling needed by as little as "a lot" and as much as an order of magnitude. Pans of water, chests of ice, these might stand a chance only if every bit of cooling possible was achieved, leaving no water left over at all.
 
LeftieBiker said:
I think that most people are underestimating the amount of cooling needed by as little as "a lot" and as much as an order of magnitude. Pans of water, chests of ice, these might stand a chance only if every bit of cooling possible was achieved, leaving no water left over at all.

Cold tap water with misting action happening (regular water pressure from hose is not enough, more like a third of pressure washer and a good nozzle(s) will do) ON the battery will have excellent result without LOTS of water wasted. I would say 0,5-1 liter per minute.
That water will cool down the air and will also make the battery case soaking wet. Pans don't work. nor does small fan outside the battery.
 
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