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Discussion Starter #1
Hi everyone.

I have an Australian 2019 Camry Ascent Sport Hybrid and it's overall a great car for its intended purpose.

I've made some observations after owning it for a year and seek feedback and comments.

When the hybrid battery reaches 35c, the car will not recharge it beyond 6 (of 8) bars on the dashboard. The Hybrid Assistant Android app confirms it, mechanical brakes are used instead of regeneration.

When the hybrid battery reaches 39 degrees, it is barely used for braking or acceleration and the petrol engine is almost always running and is used the moment you touch the accelerator.

The hybrid battery fan starts at 34 degrees and turns off at 33 degrees. It only spins at the lowest speed until about 38 degrees. In my opinion, this calibration of the battery cooling fan is grossly inadequate. It takes the fan between 4-8 minutes to drop the battery by 1c depending on cabin temperature. One stop from 100km/h will increase the battery temperature by 2c so driving in the hills creates a lot of heat in the battery and the hybrid system gives up very fast.

Furthermore, when you park the car for an hour if the hybrid battery is warm, it often continues to warm up another 5-6c as the heat from within the battery cells equializes the whole battery pack assembly temperature. I've often returned to the car after an hour and the battery pack is in the low 40c's.

High temperatures are damaging and shorten the lifespan of the battery pack. The car should continue running the battery fan on low while the cabin temperature is lower than the battery temperature for 10 or 20 minutes after the car is parked.

Has anyone experienced similar behaviour from their Hybrid Camry or have any comments?

Thanks
 

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Have you had the car to the dealer for warranty?
Dumb question.....are you riding around with the windows down, or windows up with the A/C on? Some people tolerate heat differently...and actually enjoy it. Battery gets cool air from inside car to cool battery.

Describe how this problem changes as the seasons change. I realize that your Winter is warm/hot and Summer is cool/cold.

Just some links to provide ideas...no personal experience with overheating....

For us on the °F here in the USA 35C is 95°F, 39C is 102.2°F, 33C is 91.4°F, 34C is 93.2°F, 40C is 104°F
 

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Hi everyone.

I have an Australian 2019 Camry Ascent Sport Hybrid and it's overall a great car for its intended purpose.

I've made some observations after owning it for a year and seek feedback and comments.

When the hybrid battery reaches 35c, the car will not recharge it beyond 6 (of 8) bars on the dashboard. The Hybrid Assistant Android app confirms it, mechanical brakes are used instead of regeneration.

When the hybrid battery reaches 39 degrees, it is barely used for braking or acceleration and the petrol engine is almost always running and is used the moment you touch the accelerator.

The hybrid battery fan starts at 34 degrees and turns off at 33 degrees. It only spins at the lowest speed until about 38 degrees. In my opinion, this calibration of the battery cooling fan is grossly inadequate. It takes the fan between 4-8 minutes to drop the battery by 1c depending on cabin temperature. One stop from 100km/h will increase the battery temperature by 2c so driving in the hills creates a lot of heat in the battery and the hybrid system gives up very fast.

Furthermore, when you park the car for an hour if the hybrid battery is warm, it often continues to warm up another 5-6c as the heat from within the battery cells equializes the whole battery pack assembly temperature. I've often returned to the car after an hour and the battery pack is in the low 40c's.

High temperatures are damaging and shorten the lifespan of the battery pack. The car should continue running the battery fan on low while the cabin temperature is lower than the battery temperature for 10 or 20 minutes after the car is parked.

Has anyone experienced similar behaviour from their Hybrid Camry or have any comments?

Thanks
Is this a Camry hybrid SE? Does it use the nickel metal hydride battery?
 

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Discussion Starter #4
Have you had the car to the dealer for warranty?
Dumb question.....are you riding around with the windows down, or windows up with the A/C on? Some people tolerate heat differently...and actually enjoy it. Battery gets cool air from inside car to cool battery.

Describe how this problem changes as the seasons change. I realize that your Winter is warm/hot and Summer is cool/cold.

Just some links to provide ideas...no personal experience with overheating....

For us on the °F here in the USA 35C is 95°F, 39C is 102.2°F, 33C is 91.4°F, 34C is 93.2°F, 40C is 104°F
The links were useful, thank you for sharing them. It appears many people have the same problems. I'll share some more of my thoughts. For some background, I frequently drive rural roads through hilly terrain so speeds are 60-100km/h (approx 35-60mph).

I've been monitoring the various temperatures of the HV battery, inverter, MG1, MG2, coolant, engine etc and all are in a good range. By nature of its chemistry, it's expected that the battery will warm up in use because NiMH's 90% coulombic efficiency is significantly inferior to Lithium Ion's 99% (Coulombic efficiency is how much energy is stored and returned - a lower efficiency generally means more heat is generated at charge and/or discharge. For example, if a NiMH battery captures 100wh, it can only return 90wh because the rest has been converted into heat, while a lithium based battery can return 99wh).

My only real issue with the car is what I believe to be very poor calibration of the battery cooling fan. I believe it should be calibrated to turn on low when the battery is 28-30c so long as the interior temperature of the cabin is less. This would keep the temperature of the batteries much lower, increasing both their lifespan and endurance for the current drive. I also understand that there are many other things Toyota engineers will have considered such as the battery fan drawing out air conditioned or heated air from the cabin which requires more load from the engine for cabin climate control. They may also keep the fan off for the maximum amount of time to reduce noise in the cabin. However I don't think there's any excuse for not running the fan for at least 10 minutes after the car has been shut down, if the battery is over 32-34c.

The different seasons only impact how quickly the battery hits the temperature where performance is reduced due to thermal limits. For example, if the car hasn't been driven for over 5 hours in cold weather, it may take 15 minutes of driving through hilly terrain before the battery reaches 35c. In hot weather it may only take a few minutes. In my experience, it doesn't make a difference if the climate control is on or off, windows up or down. Driving with the air conditioning on a hot day helps return the battery to a lower temperature faster, however on any drive at any temperature, once the battery hits 34c and the battery fan turns on, the battery will never go below 33c again for the rest of that drive because the software turns off the battery fan at that temperature. Once the battery is at 33c, two stops from 60kmh in a few minutes will heat the battery to over 35c, putting the hybrid system into its reduced performance mode to protect the battery until it cools down.

If the battery fan were to start when the battery pack was at 30c and turn off at 28c, it would significantly increase the efficiency of the car by keeping the battery at a lower temperature, enabling cooling of the battery below 33c when demands on it are low, enabling more energy to be captured and returned before the battery rises to a temperature forcing thermal throttling again.

I'm goal is to share my experience, discuss and hear from other owners before bringing my concerns to the dealership.

Thanks for reading.

Is this a Camry hybrid SE? Does it use the nickel metal hydride battery?
To my knowledge, all Australian Toyota hybrids are NiMH.

Mine is the mid-range model in Australia. Our hybrid models are
  • Ascent - Low end - small LCD panel, low end front and rear bumper and lights
  • Ascent Sport - Mid range - Large LCD panels, better looking bodykit and lights, a few more features
  • SL - High end - Sunroof, all the electric features
Until reading on here, I didn't know some models had Lithium batteries. I'll read up on the North American models over the next few days to learn about the differences.

Regards.
 
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