For the next few days we are expecting high humidity and 100+F temps and since I don't have much covered parking my traction battery has been taking a thermal beating and so is my mpg's that's right I've been averaging around 35's and my car has done some funky things like not turning off the engine at a stop light, reduced regenerate, no EV mode, and rpm holding when decelerating (not in B) so ya prius don't work well in extreme heat.
I had not seen that until a June heat stretch. Leaving a shaded parking spot, the car would not go into "EV" mode to creep through the parking lot. Leaving early, the car did not have a full hour of shade with the windows cracked (rain guards.) Only 95-97F, I'd acclimated enough to drive windows down but the car would not go into hybrid mode. Ten miles later while facing the sun at a bank drive-through in "P" and the engine running, I raised the windows and turned on the AC. Might as well because the engine was not going to shutoff. By the time my banking was done, hybrid mode returned even with the AC on. Bob Wilson
The worse thing, which is usually hard to do, is to fully charge the HV batt and then park in the heat. But this happens in some rare cases when people have a big downhill before parking. In these cases, run your batt down a few bars before parking. A/C good way to drain it, or EV mode if you got one..
get window shades, leave the windows open an inch if possible, park at an angle that blocks the most sun, and get your windows tinted.
I have just recently been through several weeks of temps hovering around 100F with heat index close to 110. I park in an open asphalt parking lot. I just use the front window heat shield andcrack open the front windows (window shades). The HV Battery temps have been in the 105F range in the afternoon with cabin temps in the 115F range. I just open windows, turn on AC and drive until AC is blowing cold and cabin is cooled down. Close windows and just let the AC and fan blower controls work. I am fortunate that I hit the highway in about two miles and have a 20 mile drive to help cool things down before hitting city traffic.
When the outside driving temperature got very hot this summer - I have been running the air conditioner so that the Prius' air-cooled hybrid system is working at its optimum operating temperature. I also wanted to keep the High voltage batteries and inverter system from overheating to extends their lifespan. And while I'm not get 65 mpg - I have been getting +55 mpg while moseying along about 60 mph along the Washington DC Are beltway ( I-495 ) in the slow lane back and forth to the 2015 Virginia Brickfair .
Are you monitoring battery temps? I'm typically just relying on windows rolled down, leaving A/C off. Admittedly it's a more temperate climate here, but has been getting into the low thirties (centigrade). When I have run A/C I make a point of monitoring the battery temp (via Scangauge) and I 've yet to see any drop in temp after protracted A/C use. Battery temps run in the mid-thirties typically, even on a cool evening, when the car's been running a while.
The battery thermal mass is too great to be impacted by the AC in the time intervals observed. So I suspect it is the air inlet temperature that determines if the car works in hybrid mode. Bob Wilson
I monitor battery temps and with my 20 mile highway drive I will see the temps drop from say 110F to under 100F. In the city with start/ stop driving I typically see an increase in temps even with AC and fan blower running hard in hot weather.
Interesting. The only thing I'd question: if you did the same drive without AC would there be some amount of temp drop?
I have not tried without AC but have tried switching from recirculate to fresh air. The battery fan intake air temp will drop initially but then the hot outside air will cause the cabin temp to increase so all of the temps start to rise. It works best to leave the AC in full automatic and let the Climate Control System and HV Battery fan work as designed. No AC with 100F temps, I will let someone else try that on their car, not mine.
Update: So this week we had and unusual strong cold front came in drop our temp to the high 80's with low humidity and my mpg is up to 55.5 mpg using same fuel, and same air tire pressure, driving habits. Temperature play a great role in mpg as it really affects the battery performance. I only wish the next generation prius will have ac cooled battery for better mpg consistency.
Our lows drop down to low 50's even in the 45's in some area, so yeah it was time to bring out the coats this morning.
With 100 F outside temperature I've seen 165 F inverter temp. and TB temp. 47 C. I haven't had my 2013 Prius go to cool down survival mode yet. See attached picture of EngineLink HD showing 165 F inverter temp. Cheers!
