Battery temp continued to rise after car turned off

The cooling fan won't run with the power off, the pack is influenced by the cabin temps (you said you parked in the sun; what was the inside temp?) and there might have been some residual heat in the pack from driving.

I haven't experienced this but it doesn't seem that surprising to me.

 

Just like your coolant temperature will rise after you turn your car off. Uncirculated coolant starts to increase in temperature because it's transferring stored heat in the engine block. When you turn the car off, you are turning off the cooling fan. Residual heat in the battery causes the temperature reading to rise slightly due to lack of circulation.

 

Pretty good info. A little drawn out but informative. https://www.youtube.com/watch?v=tf0FMoY3Cs&feature=share

 

I don't have any first-hand knowledge about these folks (in Worcester - they run hybrid repair training and certification classes), but they turned up in my own searches for a Philly area hybrid mechanic: Auto Careers Development Center - Hybrid And Electric Vehicle Repair Training . Craig Van Batenburg responded quickly to an email I sent him. I'd suggest getting in touch with them; they also have a shop finder on their site that lists Tosti's Service Center in Framingham (and a few others, but further from you). If anyone has experience with shops in Boston area, please chime in!

 

Yes this is true about the temp increase.
This why you shouldn't park in hot sun with HV Battery totally charged up...at least for Gen2.

IIRC, one of the national labs had a unique issue, I think it was with Gen2 Prius owners some years ago. The workers, coming to work, go down a huge mountain and their HV batteries get totally charged up (in the top green for us Gen2 owners). Then they would park in the hot sun. The batteries on some the Prii did not hold up to this.

The solutions was to try not to park in heat when you are totally charged up. You can for example put the A/C on to drain the battery down a few bars. I do not know if Gen3 and Gen4 computer logic helps to prevent this issue or not.

 

Your temp rise after the car was off was not because it was parked in the sun. It was because the energy released (heat) was trapped inside the battery and it takes time to leak out. Remember, the sensors don't measure the temperature of the whole battery, just the temp. where they are located. So the temp they see will rise after shutoff. Also, remember, the battery cooling fan is not perfect. In fact, it is very imperfect. Air is a very poor fluid to transport energy. It takes a long time for air to cool the battery, even longer when the battery cooling fan is not running (for example, when the car was off). In fact, in houses, we use air to -insulate- the house!

The loss of battery power when hot was the system protecting the battery, reducing the power the system can use to avoid heating the battery too much further.

Running the battery fan when the car is off could help, but we just don't have the power capacity in our wimpy 12V battery! Using a liquid cooling system for the traction battery would help more, but would add weight and complexity.

I think what you saw is very interesting, but normal.

 

Hi Roger T,

Try to remember you are driving a Hybrid. Basically, you are driving a motorized computer system. Within the computer system is pre-installed back up system software to assist and keep it running as best as possible. Hot weather really puts the computer to work. For me, I have noticed that short distances (stop, go to CVS pharmacy, pick up over the age of 50 drugs, go, stop by the grocery store to pick up "hunny-do" items, go, stop and go back to CVS pharmacy to pick up........you get my drift), short distances really make the battery work hard. In really hot weather, I go from full bars to 2 bars really fast when doing start/stop/shut-off driving. Once I thought I was going to have to go to the dealer. But, after letting the car sit for 5 hours, I went to my car and mysteriously my bars were 3/4 full at start up. The Prius is really a smart car. Smarter than the driver when it comes to maintaining itself. Give it some time. See if the patterns stay the same. I did, and the patterns seem to stick. Hybrids are just different cars. You will hear buzz sounds, beeps, tones, clicks..........etc. LoL!

 

Having a Prius almost prepared me for my new HE washing machine. Now that's a whole different experience!

 

I noticed a big dropdown to no Regen amperage during hot days after the recall update.

 

Roger, I have a scangauge on my CMax Energi and although it may have different battery chemistry I can confirm similar observations with heat. Ford shuts down the EV party @ 113f and makes the car revert to hybrid operation until the pack temp drops lower. Even though I live in a hot area (101f yesterday), I've never experienced this mode. I try to park in the shade during the day; especially the afternoons.