Cooling an electric vehicle battery. (2023 Update)

torsdag den 9. september 2021 kl. 10.08.09 UTC+2 skrev snipped-for-privacy@ieee.org:

Tesla batteries are liquid cooled (or heated when needed), there's a glykol filled flat tube that zig-zag between the cells

Here's a video of one that's been chopped apart:

I don't know what shape the cells in the CATL LFP batteries (used in Shanghai manufactured model 3 sold in Australia at present).

Tesla has a tube that runs thru the cells, the Chevy Bolt uses similar design to BMW where there's a coolant plate under the cells.

I own a discontinued Chevy Volt plug-in hybrid which has a third design where the coolant runs in channels through plates in-between the cells which I think may be a little more efficient thermally than the previous two but it's not a compact solution and constrains the size and geometry of the pack more I believe, it's down the centerline of the vehicle amd tall which compromises the interior space a bit.

It has three isolated coolant loops one for the engine, one for the power electronics, and one for the battery, and the engine loop is used to bring the battery loop and cabin air up to temp quickly on very cold days, as it's more efficient to burn a few drops of gas to do this than drain from the pack which is small by modern standards.

All the loops use DexOS 50/50 as coolant, deionized water/ethylene glycol.

Same for the Bolt, there are heat transfer plates between cells, with small pipes zz over the flat plate.

The Volt and Spark EV used that design, but I believe the Bolt is more similar to BMW there's a coolant plate under the cells, not in-between.

The other advantage of cooled bottom-plate is that it can be load-bearing and pull double-duty as the battery tray and provide rigidity to the frame.

The Tesla coolant loop design is probably the best from a cost/efficiency/reliability three-legged stool standpoint.

OK, but heat travel up, more than down, at least for the air flow. I am considering removing the top plate of my Leaf battery to cool it. The bottom plate is heavy and rigid enough. However, it will no longer be an air-tight submarine, and my next dive would total the battery.

I did drive the Leaf into a flooded ditch, up to the floor of the car.

The "safing" method for the Mitsubishi iMieV's battery if the pack is say damaged in an accident or something is you disconnect, pull a few ports open, and pick the whole car up with a forklift and place it in three-foot deep pool of water for 24 hours.

Not kidding, it's in the service manual lol

Don't quote on that depth, it might have been more like 18" of water, three feet a lotta water

My Leaf was floating in about 15" of water, but it won't sink any further. The carpet was wet, but no volume of water. It was in the water for couple of hours until someone pull it out with a pickup.

I think it would be safe as long as the bottom case is water-tight with the car frame. The battery can then be cooled with the passenger compartment A/C.

Recently, from Fresno to Bakersfield, after 5 consecutive Free Fast Charging, the battery reaches 120F. I ended up with long breaks just to cool it down. The HV shutdown port (only access to the battery) did not feel warm at all. The battery is too well insulated.

I can't say how much of the claimed 15% energy loss is dissipated during charging vs. discharging, but assuming they are even approximately even, the discharge has much higher heat generating potential because the highest power is during discharge. My car can generate 400 kW easily when I mash the pedal. Even though this energy is seldom continuous, it releases significant amounts of heat into the motor and battery. I normally drive relatively flat terrain, but in mountainous areas I expect such high numbers would be much more protracted. When towing it would be even worse. While most ICE vehicles are designed to dissipate such heat, EVs are typically not designed to dissipate such heat on a continuing basis.

??? Not sure why that design comes to mind. The Tesla batteries have coolant flowing through them. This eliminates the delta T required to push the coolant through the heat pipe and heat sink. The heat transfer is powered by a pump as on nearly every type of vehicle. I don't know a lot about many of the various EVs being designed today, but the Nissan Leaf does much less to control the temperature of the battery with the resultant shortening of the battery life.

Nobody does what exactly? It is hard to imagine an EV maker who isn't aware of the need to control the battery temperature. Nissan aside I expect going forward they all provide battery cooling. Are you suggesting your heat pipe idea is a better way to accomplish this?

Batteries are not made of air currents,and conduction is usually able to transfer more heat than convection anyways.

Sounds clever.

For older model Leaf, there are spacer bars between cells with a cooling air gap. So, forced air from the bottom should help.

Yes, embarrassingly clever to cool down. The area looks flat off the road, from a distance.

Is the spacing for cooling or expansion or explosion/fire mitigation? I haven't torn one apart to see myself. Are there blowers to move air through these channels?

Did you drive into a lake?

Yes, it's allowance for expansion.

Not currently, but i plan on adding blower pipe from the HV cutoff port (in the middle of the passenger compartment). Someone actually build a 3D model for an adapter for it. But it won't work too well without exhaust holes.

It was just an open area off the road. It looked like flat area for a quick stop, at least for the surface.

Here is the link:

All because he is too cheap to buy an EV that actually manages the battery temperature. This guy is the poster child of how not to drive an EV.