Battery Cooling

[Iowa92x]

Why is an ICE radiator able to keep 1,200 exhaust temps in check, but the cooling system on a Tesla is unable to keep a 150 degree battery temp under control for one lap on the track?

Batteries get maybe 1/8 as hot as a gasoline engine, what technical barriers are there to keeping battery temps low enough for sustained high load runs.

 

[newtman]

Well for one thing the typical mass of a V8 ICE engine is ~500lbs while a Tesla battery weights 1200lbs; that's a lot of mass to cool. Secondly, the exhaust temp is quite a bit higher than that of the actual ICE engine, and it's being immediately vented out the exhaust system, and doesn't need to be dissipated by the cooling system.

 

[Iowa92x]

I wonder what the max battery temp is before the car goes to limp mode? 150 degrees? I wouldn't think it would be a complex problem to solve, but obviously isn't an obvious fix, or they would have obviously fixed by now.

 

[kptesl]

Why is an ICE radiator able to keep 1,200 exhaust temps in check, but the cooling system on a Tesla is unable to keep a 150 degree battery temp under control for one lap on the track?

Batteries get maybe 1/8 as hot as a gasoline engine, what technical barriers are there to keeping battery temps low enough for sustained high load runs.

It takes much more cooling to keep something below 150 degrees than it does to keep something below 1200 degrees. Engines and exhaust components are all metal and ceramic and can survive high temperatures. Most lithium ion batteries contain organic liquid (as lithium doesn't play with water) or polymer electrolytes that cannot withstand temperatures even close to that.

 

[brantse]

I haven't monitored it often, while driving, but on occasion have watched the battery coolant temps using TM-Spy. IMHO I really can't believe how good the thermal management system is. I don't believe I've ever seen the temperature spread beyond 2 degF and I believe the temperatures were normally in the low 80's.

That said, there's a big difference between trying to maintain temperatures in this range, compared to normal ICE coolant temperatures of 200'ish degF. Cooling capacity for any system is directly related to the temperature differential between the medium and it's heat sink; so the closer the operating temp is to ambient, the more difficult it is to cool.

 

[Iowa92x]

I haven't monitored it often, while driving, but on occasion have watched the battery coolant temps using TM-Spy. IMHO I really can't believe how good the thermal management system is. I don't believe I've ever seen the temperature spread beyond 2 degF and I believe the temperatures were normally in the low 80's.

That said, there's a big difference between trying to maintain temperatures in this range, compared to normal ICE coolant temperatures of 200'ish degF. Cooling capacity for any system is directly related to the temperature differential between the medium and it's heat sink; so the closer the operating temp is to ambient, the more difficult it is to cool.

Best reply yet, thanks!

 

[David29]

Would it be correct to say that it is somewhat easier to obtain the energy from an ICE engine to operate the cooling system (i.e., rotational motion to power a coolant pump, and possibly rotational motion for a cooling fan when needed)? I imagine it is "almost free," that is that the power load from a coolant pump and possibly a fan is a very small demand for the ICE. Whereas the Tesla battery requires A/C plus the pump and fan, all from the battery.

 

[Tennisballer]

The cooling system on an ICE car is for cooling the engine block not the exhaust only a boat cools the exhaust and that uses the lake water to cool it. The ICE now a days is kept around 225ish on purpose but it is a lot easier to cool that then a battery/electric motor doing strenuous work. When a thermostat sticks open the ICE will remain below 190 all the time in winter even colder it has a thermostat in order to get the engine that hot enough for operating range. The battery is not cooled in the winter most likely cooling occurs during charging mainly during the winter or during extreme acceleration. In order to put the amount of power that a SC puts in creates enormous heat much more that an engine block could produce. In racing applications an ICE runs on alcohol and requires no coolant at all, the fuel cools it.

 

[mgboyes]

Why is an ICE radiator able to keep 1,200 exhaust temps in check, but the cooling system on a Tesla is unable to keep a 150 degree battery temp under control for one lap on the track?

Batteries get maybe 1/8 as hot as a gasoline engine, what technical barriers are there to keeping battery temps low enough for sustained high load runs.

Because keeping something cooled to within 100 degrees of ambient is much harder than keeping something cooled to within 1000 degrees of ambient.

 

[Brass Guy]

Also note that since Tesla's battery tries to maintain 70-80F (guessing here), sometimes that's even cooler than ambient (see Arizona); therefore needs active cooling using a compressor. An ICE never needs that kind of cooling because ambient temps where we drive are never above 200F.

 

[apacheguy]

It is not the battery. It is the drive unit. There is no way you will heat up the battery from 30 C to 52 C just by doing one lap around the track. There is a huge amount of thermal inertia.

 

[apacheguy]

Also note that since Tesla's battery tries to maintain 70-80F (guessing here), sometimes that's even cooler than ambient (see Arizona); therefore needs active cooling using a compressor. An ICE never needs that kind of cooling because ambient temps where we drive are never above 200F.

Tesla batteries maintain a passive target of 30 C. This is 86 F.

 

[ERP]

Another small factor is that during braking on an ICE, the injectors shut off when the throttle closes. This stops new heat from being put into the engine for a short time. But on the Tesla, the motors become generators and convert mechanical energy back into electrical energy. Some heat is generated from the inefficiencies. I am curious if the Tesla would last a little longer around a track if the regen is set to low.

 

[Saghost]

Why is an ICE radiator able to keep 1,200 exhaust temps in check, but the cooling system on a Tesla is unable to keep a 150 degree battery temp under control for one lap on the track?

Batteries get maybe 1/8 as hot as a gasoline engine, what technical barriers are there to keeping battery temps low enough for sustained high load runs.

What makes you think it's the battery?

The best guesses I've seen have pointed to the battery pack main fuse being the limiting factor - and the folks with Ludicrous cars report that it is much, much harder to get them into limp mode with their fancy smart fuses...