Engine running on EV mode

To help warm the cabin, my guess

 

Heat pump systems (of all kinds) typically shut down below a certain temperature due to lack of efficiency. The engine then will take over the heating of the car. I think the cutoff is around +17.

 

agree with all above, what do you have the heat set to?

i went 9 miles this morning at 10 degrees with the heat off, all ev.

 

It was 11° here today and I noticed the same thing. The engine ran intermittently during a 15 mile trip and the return trip two hours later, even when the battery was fully charged. I was using heat, but not Front Defrost. I've never seen that happen before, but 11°F is the coldest we've had since I bought the car. I generally keep the heat set at 64°F.

Two other observations:
1. Running the Front Defrost when the weather is at all cold (about 40°F or below) will start the engine, which will keep running even after Defrost is turned off.
2. Using the Remote Climate control in Entune for 10 minutes with Max Heat and Front Defrost (followed by about 20 minutes of charging) generally uses less than 1 kWh of electricity, but helps extend range and efficiency in cold weather. However, if I accidentally turn on Front Defrost while driving, the engine comes on and stays on as above.

I think this behavior is intended to maximize electric range at the expense of using some gasoline. By starting the engine proactively, the waste heat can be used to warm the car while it runs in hybrid mode. After it warms up, less electricity is needed to run the heat pump so it becomes more efficient to shut the engine down and use residual heat. But after then engine partly cools down, the control system restarts it again. I noticed two or three cycles of this on each half of my trip today.

 

It's been cold in the northeast recently under the said 14 deg F cutoff, and I have noticed that EV mode is hit or miss when it is that cold, even if there is battery charge left. I figured there was something in the owner's manual that mentioned it, but hadn't gotten around to looking back to it until i saw it posted here. I had the climate set to around 68, of course didn't lower it / turn it off because it's pretty darn cold in the cabin otherwise

I was actually parked at the mall the other day and had disconnected the charging when I had about 70% battery and noticed that when the in-dash temperature reached somewhere around 12 deg F the ICE started, at the previously mentioned climate setting. It switched on/off sporadically in the ride back home.

 

At these temps don’t let your gas tank get low, small tank, hungry ice.

This forum is almost impossible to post to with an iPad, the forum just keeps eating the page and changing it, bad forum bad dog

 

I've found two things that can greatly improve EV mileage and help avoid having the engine run in cold (12F to 13F) weather. The first is to use Remote Climate to preheat the car before driving it. With the car on the charger, I run one ten-minute cycle at Max Heat plus Front Defrost (followed by about a recharge taking about 15 to 20 minutes), which seems to be enough to prevent the windshield from fogging. Two preheat cycles might be needed in extremely cold weather, but my goal is to achieve about 40F to 50F inside the car. Since driving doesn't require much physical work, that is a comfortable temperature with my winter coat and gloves.

To prevent the engine from starting during the trip, I simply turn off the AC by setting the Fan to OFF. To keep my hands warm, I run the steering wheel heater at least part time. (If you don't have the steering wheel heater, using the seat heater and wearing gloves might also work.)

For comparison, I made two trips to my local grocery store (6.9 miles) on separate days. In each case, it was the first trip of the day, and started after preheating the car as described above and then topping up the charge. The first trip was at about 13F and using the AC set to 64F for heat during the trip. On that trip, AC load was 28% and miles/kWh was 2.6. Perhaps surprisingly, the gasoline engine did not come on during the trip.

Today the temperature was 12F, and I went to the grocery store again, but with AC turned off and using only the steering wheel heater for heat. This time the AC load was 2% (presumably due to the the steering wheel heater), and miles/kWh was 3.4 (about a 30% improvement). The only other time I have seen AC load as low as 2%, the outside temperature was 67F!

I don't have comparison data for 12-13F without preheating, but so far I've found that preheating almost always eliminates the need to run the front defroster while driving, and thus helps avoid running the gasoline engine at winter temperatures. (It is probably not worth running the rear defroster during preheat unless there is snow or ice on the hatch.)

Tentative conclusions: At least in very cold weather, electric resistance heat can be more efficient than heat from the heat pump, thus extending electric range and avoiding gasoline use. Preheating is also helpful because it avoids having to use battery charge or gasoline to achieve the initial desired cabin temperature. If your goal is to use EV mode as much as possible, these techniques will help, especially on short trips.

 

I love that list from Toyota... they could have left the entire list out and just left it at: when the system determines the gasoline engine needs to be started. Doesn't that sentence fill all of the above conditions? And the follow on sentence (the gasoline engine may also operate in circumstances other than those listed above)... really? like it may start when the system doesn't think it needs to be started? What's left, a random number generator?

Back on topic, do a search, there's been lots of discussion about things that cause the ice to kick on (like going downhill with a full battery on ev), cruise control under certain circumstances, etc.

EV mode should really be: We'll *try* to keep you in EV mode, but we may just switch out randomly for our own reasons and not tell you why so that the chat groups have something to talk about.