High Temperatures, effect on batteries?

Toyota limits the HV battery usage if its temperature is too high. You better use the A/C to help cool the battery in such hot weather. Good luck!

 

use the mfd (screen) to set your a/c fans on medium. turn recirculate off. you want cabin pressure.

slow & steady on the accelerations.

(stay away from neutral... off topic, i know.)

 

Heat is an enemy of battery life, so as 2009Prius suggests, the car takes protective steps when the battery gets hot, including reducing its usage. So in hot weather, especially if state of charge is low, the car will feel sluggish and you'll need more ICE power than usual for a given amount of acceleration and cruising speed.

I can and do monitor my battery temperature. The more hot weather I experience with the car, the more convinced I am that running the AC makes little difference. We've had a spell of unusually hot weather (for Virginia) the last few days, with daytime highs approaching or exceeding 100F. To save fuel, I don't usually run the AC, but I've been running it this week on my afternoon commutes. On a good day, battery temperatures still start in the 90s and often rise to well over 100, even with the AC running -- or perhaps in part because of it. Using the battery heats it, and the AC runs off the battery. On a long highway run the battery eventually cools to below 100, but it's a large thermal mass and it takes its time.

I've offered this advice in the past, but I believe even more strongly in it now than before: Take all reasonable steps to keep the battery from getting hot in the first place. First and foremost, I always try to park in a shady spot. I have tinted windows and I use a windshield sunshade. I crack the windows, with WeatherTech deflectors to prevent the undesirable effects on the car's interior of a sudden storm.

 

The humidity in this area is so high that simply rolling down the windows just means you'll have a heat stroke, so I'm glad that running the AC does help the batteries to some degree. I also use a sunshade on the windshield and try to park in the shade, hopefully I'll have a chance to get my windows tinted soon... it seems like everywhere I call is booked for weeks!

 

I run the AC constantly, set for 75 degrees F, and my indicated mpg is in the high 40's. If you enjoy being in the car without AC when the temp is in the 90's that's your business - but if your motivation is merely to improve mpg you may find that AC use does not have much adverse mpg impact.

In general batteries do not like excessively high temps so you can expect a shorter service life will result from constant exposure to such temps. If you wish to mitigate the effect of high temp, then the obvious solution is to run your AC so that moderate cabin temps result. Good luck.

 

You need to run your ac!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Not just battery life but also fuel economy. When the battery control system gets too hot it has to throttle itself, as 2009P mentioned above. If you're too hot then the battery is too hot, so do yourself a double favor and run the A/C.

 

Remember the battery works best when the temperature is between 70 & 80 degrees.

 

With all respect to the quite knowledgeable and always-helpful Patrick, it might seem obvious but it's not. Again, my direct observation of battery temperature suggests the AC's effect is negligible at best on short to moderate-length trips. On one of my afternoon commutes (12 miles) this week with AC running the whole way the battery started at 100F and rose to 107F by the time I got home.

On the other hand, it seems logical that the control system that Richard mentions would respond more quickly to a cool cabin.

Still, I generally avoid AC (except when we approach triple digits or humidity becomes unbearable) and my summer commuting fuel economy averages around 80 MPG. It drops considerably when I turn the AC on, mainly from the the significant current draw on the battery in my suburban driving environment.

 

80mpg!! What do you drive like 25mph. I am admittedly a newbie at this but using the techniques of the Prius knowledgeable I seem to be right at 50mpg ...with A/C on. If could improve it by that much I would consider losing the A/C on the more bearable days.

As for the battery temp I wouldn't think the cabin temp would have a huge impact on the battery ....but I guess with that vented area it can help some.

 

The battery is pretty heavy (99 lb) so once it heats up, the flow of air over the modules will have limited cooling impact especially on a short trip. The air doesn't get to circulate between the modules which are sandwiched together.

My preference is to give the battery a break by making cool air available. 75 degree F air seems better than 100 degree F air from a cooling perspective.

The battery vent fan draws air from the vent next to the right-side rear passenger seating position, and exhausts the air at the right rear of the car (outlet vent is hidden by the rear bumper cover).

Since the OP noticed an improvement in vehicle responsiveness once he started to provide cooler air to the battery, that provides evidence that battery performance can be impaired at higher temps.

 

Sure does seem that way. I didn't realize the vent by the driver pulled cabin air in and vented out the back as you note. This car really is smart engineering in every aspect. Frankly until the OP I didn't give the battery temp much thought. Thanks to all for input ...I run my air at 74 most times and things have been ok thus far. It has been humid and in the mid 90's here the last week so it's being tested for sure.

 

So does anyone know which if any of the climate control settings effect the battery air flow?

Meaning if I have it on foot vent only, does some go back to the batteries? Or is it always going to the battery area as long as the fan is on some speed?

 

Pretty close. See this for more on my morning commute. Posts 9 & 14 provide a quick list of how I get these results. One thing the list doesn't include: I avoid AC at these speeds when I can tolerate it, which is easily done at 6 am.

 

It seems to me that inevitable HV battery temperature rise should be
combat-able by driver choose-able HV battery cooling fan operation.

Is there a published hack/work around/DIY on this?

It seems pretty straight forward that being able to push air through the
HV battery at ambient temps below 100 degF, well before the HSD calls
for the fan and reduced HV battery availability, would at least delay, if
not prevent, HV battery overheating. (I'm thinking of temps rising while
driving, not from a hot soak in a uncovered parking lot, etc.)

You wouldn't necessarily need a ScanGauge or equivalent to use this
tactic effectively. Except in really cold OAT, overuse of the HV battery
cooling fan would be a small inefficiency, but not damaging.

 

The climate control settings have no direct impact on battery air flow. In fact the climate control system does not need to be turned on.

The relevant issue is the temperature of the air near the rear passenger seat, since the vent at the right rear passenger position is the inlet for the battery vent. You may have noticed the battery fan running at different speeds as the battery heats up. If you hear the fan running at a high speed, that is an indication that the battery is under stress.

The Classic Prius has a turtle warning light that shows when the battery needs to rest. This light was eliminated for 2G. Instead your warning is hearing the battery fan speed up.

 

In Miami, even if I garage the car during the day, the temperature issue is a nightmare. Even if the entire night is 81oF, the battery is a minimum of 90oF first thing in the morning. 15 minutes of running with or without AC and the battery is already 102 or so.

It the car is left in the sun for a quick run in to a store, the damned battery is over 114oF and forced EV mode is prohibited. Running the AC does nothing at all to bring the battery temperature down.

I've seen my HV get up to 126.

I hate the darned heat.

2007 Prius.

 

I think I'd move north.

 

looks like that heat finally took its toll.