Battery issues

I wouldn't buy that explanation. It isn't finicky, mode changes happen for a reason.

There are some things that will cause the ICE to come on - defrost mode, cold temperatures (less than approx 14F) with the heat on, etc. From your owner manual:

■Gasoline engine operation in EV/EV auto mode

Even if there is a sufficient amount of electricity remaining in the hybrid battery (traction battery) and EV driving range (P. 199, 215, 222, 239) is being displayed on the multi-information display etc., EV driving (driving using only the electric motor) may be canceled and both gasoline engine and electric motor are used depending on the situation (EV driving will be returned to automatically after EV driving becomes possible again).

EV driving may be canceled automatically in the following circumstances:

●When vehicle speed is more than approximately 84 mph (135 km/h).
●When power is needed temporarily, for example when the accelerator pedal is depressed firmly or when accelerating suddenly.*
●When the temperature of the hybrid system is high. The vehicle has been left in the sun, driven on a hill, driven at high speeds,
etc.
●When the temperature of the hybrid system is low.
●When the heater is switched on when the outside temperature is below about 14°F (-10°C).
●When the windshield defogger switch is pressed. (P. 492, 502)
●When the system determines that the gasoline engine needs to be started.

The gasoline engine may also operate in circumstances other than those listed above, depending on conditions.
*: When traveling in the EV auto mode only
■Conditions in which the gasoline engine may not stop
The gasoline engine starts and stops automatically. However, it may not stop automatically in the following conditions*:
●During gasoline engine warm-up
●During hybrid battery (traction battery) charging
●When the temperature of the hybrid battery (traction battery) is high or low
●When the windshield defogger switch is pressed. (P. 492, 502)
*: Depending on the circumstances, the gasoline engine may also not stop automatically in situations other than those above.​

 

Fire that dealer and find another. They clearly know little to nothing of the Prius, let alone the Prime.

 

welcome!
i would expect electric mode to 'kick on and off' in ev auto, no?

 

I don't think that is good advice at all.
Given the quote provided from the manual, I think most owners would find "finicky" a good description of it's normal operation.

 

A good dealer would have noted what jb posted from the manual and tried to help figure out what caused it. A bad dealer calls it finicky.

 

Those seem like pretty EV-friendly temperatures to me. But if you're accelerating a lot, braking a lot, or going up and down lots of hills, the battery or inverter can get pretty warm. The only time I had an "issue" like that was going down the north side of Grand Mesa in Colorado. It was a chilly day -- heavy jacket temps at the top and long sleeves at the bottom. The slope charged my battery from 10% at the top to 98% near the bottom when the engine came on. By the time it finished its warm up cycle, the EV system was cool enough for me to drive in EV till I switched to HV at about 10% charge while making the climb up the Colorado River.

If it's like that from the start, I'd be concerned, but if it's taking a while to warn up and show those characteristics, I'd call it normal.

 

Yup @bisco is correct.

In EV auto, you'll drop in and out of EV/HV. That's why I NEVER use it and manually swap between the two. You'll make much more efficient use of your battery charge.

Oh and if your dealer knows anything about the Prime that should have been the first thing mentioned. Usually the mechanics would know, but the sales people are usually less.. um .. knowledgeable.

 

Canyons usually mean long steep hills, and that can definitely force the engine to come on. It's most likely on the downhill if you're braking (or using B mode) a lot. But it can happen on the uphill too.

Since you're in Utah, I think I-80 from Park City to Salt Lake or either of the Cottonwood canyons would be long and steep enough to turn on the engine sometimes. I haven't driven my Prime there yet, but they seem similar to Boulder canyon or some of the mountain passes in Colorado.

 

On my car, I noticed that when I'm climbing a steep grade in EV mode, sometimes the engine will kick on. Maybe it's due to the amount of charge in the battery I have left, but I don't think so. The engine is supposed to kick on in EV Auto mode when you need more power, like passing or accelerating to get on the freeway.