Traction Battery Cooler Experiments

One approach might be to charge the battery early in the morning, just prior to driving it, when the ambient temperature is the coolest. If you drive it home late afternoon/early evening, then let it cool off for as long as possible until you charge it.

One thing you might note when you do the experiment is the air temperature going to the battery and the fan speed (if your app shows that). I think Hybrid Assistant shows both.

 

Yes. That is the air going to the battery.

 

My traction battery slowed down charging last time due to heat, since that day I ensure AC in my cabin is cool before I park the car back to the garage when I get home (based on forecast).

And of course "Get Ready to react" with the 5 seconds pop up to enable AC during charging after power off. So far I haven't seen that message when my cabin was cool/freezing

My daily charging schedule is usually 3-4 hours cooled down before it kicks in around 7:45pm (when electricity is the cheapest). I usually leave at 6am to work so I have allowed it to cool down a bit after the charging schedule is completed. So far I am ok with that schedule.

My area temperature with humidex is about 47C/117F today so I will be ready when I get home to meet that pop up

 

Cool experiment. I have seen the battery cooler pop-up message only once in last two years, but looking at the temperate data from Hybrid Assistant, the trigger temp must be higher than 90F. Yesterday at the end of my afternoon commute, the battery temp was shown to be above 90F, but I did not see the pop-up. See graph below.

Since I don't usually look at the screen of Hybrid Assistant App while I am driving, I am not sure if the real time data is displayed on the screen of the App, but the report generated shows data for "Battery Inhaling Temperature". This temperature is different from "Room Temperature". Yesterday, I had car parked in sun, so the inside room temp was very high initially compared to cool outside ambient temp. Strangely the battery inhaling temp is much lower than room temp initially but higher than ambient temp as shown in the graph below. I think if the ambient temp is lower than cabin temp, the battery fan somehow intakes air from outside.

 

That was my thought. When I run Hybrid Assistant I rarely look at the screen display. The reports have the real data that you can study at your leisure.

I don't think this is the case. The air intakes are at the back seat side, and this may just be a cooler location in the car or the sensor might be down inside the air intake tube nearer the battery, which would be under the seat or under the rear deck.

This is a good post. It's screaming hot here today, so I may make a recycling run and see what Hybrid Assistant shows, even on that short run.

The last three days after driving 11 miles home after the car sat in the sun at 95F +, I did get the infinitesimally quick battery traction cooler question and answered yes. I don't know if it changed anything, as the car was always at full charge at 0620 the next morning as I had programmed it.

 

You might be right. Now looking at the graph again, it is strange to see the data showing initially higher room temp vs lower inhaling temp reversed during my trip around 16:09:11, becoming higher inhaling temp than room temp. If the sensor for the inhaling temp is located near the battery as you suggested, it does explain why the inhaling temp get hotter as the battery works longer while the room temp is getting cooler.

 

Since our temp rarely gets high, I almost never see the battery cooler pop-up message at the end of a trip. Even if I see the message on some unusually hot day, I am likely to ignore the message for I do the charge over night just like you. Our night temp is always below 70F, and car being outside on my driveway, it is very unlikely there is any need for the battery cooler to operate before or during nightly charging session.

 

You might get one of those cheap thermionic coolers that plug into the rear12v outlet to blow air into the front of the cooling fan under the rear seat. Since the 12v rear outlet does not stay on when the car is turned off, it will not drain the 12volt.

12V 6A Thermoelectric Peltier Refrigeration Cooling System Kit Cooler Fan DIY US | eBay

 

I don't think this will improve anything. The air directly out of the cooler might be a bit cooler than the cabin temperature, but the waste heat from the cooler goes into the cabin, so you are just adding the electrical energy input to the cooler as overall cabin heat. If the car runs the HVAC system during charging, the waste heat is rejected outside the cabin, which results in net cooling of the cabin.

 

It would be nice if Toyota can add all this type of information into our existing dash panel. Lots of space for that

 

I usually ride with my windows down. I do 48 on the highway on a 55 mile an hour Zone. The reason I leave the windows sounds so I can feel the nice breeze coming into the car which directly will go into the two vents in the back . The air is not hot if it was that we roll up the windows and use the AC. But it doesn't matter if I ride with the AC on or if I ride with the windows down. It's a guessing game when it will ask me about cooling the traction battery when I turn off the car. Sometimes I can ride with the AC on and then drive home and it was say ask me to use the AC to cool the traction battery. Other times when I ride home with the windows open similar temperature inside the car and it doesn't in for me to use the AC it's cool the traction battery.. what I can say is it hit or miss on the temperature of the battery and how much air is circulating and traveling through that battery vent.

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Last Friday when I got home, my cabin temperature was ICY/AC cool and outside temperature before power off was 31C/88F (habit to get ready to flip and push) finally the pop up display showed up. Looks like it is an outside temperature sensor thing?

I agree with windows down and let the air comes in will circulate the back vents better even with AC on (longer battery life). But the pop up display to cool the traction battery during charging could be an outside temperature thing and very inconsistent. Toyota needs to fix this flaw to allow us to choose in the menu and not to guess when to turbo our mind/finger game

L2 is better and more convenience in every ways but isn't fast charging usually degrades the battery faster compare to slow charging?

 

Since I don't have access to pack temps currently do you mind if I ask you for some help determining the diff between L1 and L2 charge temps?
I understand if you don't want to waste 4 or 10 extra hours to do the comparisons (10 extra hours if the charge setting is changes to 8 amps on the MID) just for me or anyone else interested in pack longevity if only to get your take on the difference in L1 and L2 temps in hot charging situations. I only ask as I'm very interested in pack longevity and to get at least one baseline comparison, if you have the time and interest as I do. thanks.
I get the windows open message in the MID a lot too.