I have just bought a 2017 Prius Prime and have a question about driving it in EV mode most efficiently. I have short enough commutes that I seldom use the hybrid mode - so range is not an issue. Being retired, speed to the destination is not critical either. It seems gradual acceleration and deceleration are ideal. When cruising steadiness in speed is important. However it is not clear what is the most efficient mph to travel when cruising. (Normally electric motors have some speed at which they operate most effficiently). Related to the above, is there a stiff penalty for cruising at 60 mph down the freeway? Thanks for your thoughts on these questions. (I hope didnt miss an earlier discussion of the above) Bill
welcome! i don't know for sure, but have been told in the past, the slower the better'. if your route is 60mph, what are the options?
Look for a delivery van or semi-trailer truck to follow using dynamic cruise control. Avoid dump trucks, garbage trucks, and hauling heavy equipment movers. What happens is following traffic will see you are 'stuck' and smoothly pass you and the truck without tailgating. Bob Wilson
I can drive slowly on the surface roads so no problem there. On our freeways, 60 is the upper speed limit. In town 40 is the lower speed limit. So no legal problems at 40 but all the ICE fly by. My old 2005 Prius Hydrid was supposed to be best at 40 so I thought the Prime might have a suggested speed too.
not sure about the old 40mph thing, there is an efficiency curve for engines, but if you're steady state, it doesn't really come into play, because the engine isn't remaining at one single rpm like a gasser. your best bet is to take the route that uses the least electrons, that would be the most efficient.
I haven't yet heard of an optimal speed for the Prime. I've been having success driving the Prime similar to how I drove my previous Prius. To whit: brisk acceleration, maintaining a constant speed with a light foot, long slow light-braking deceleration, and anticipatory driving. Pretty much, a lot of what I wrote about here: Tony Schaefer on Hypermiling » What Drives Us
I think your 40mph is a good target. I've noticed that if you're forced to stop and go a lot, even at slower speeds, you pay a penalty. I've found that driving 10mph faster and never stopping, if possible, yields better results. The big killer is having to drive up hills. For that reason, I always drive downhill! .
Actually under 42 mph and 38 mph worked best because above 42 mph, the engine has to run. In the Prius Prime, just keep the speed under 84 mph because above 84 mph, the engine has to run. A heads-up, turning on the front windshield defroster also turns on the engine at any speed. Bob Wilson
For 60mph, I would suggest HV mode unless your destination is within EV range and you can charge up at destination, or your round trip is within EV range. Those who have driven at highway speeds have seen the battery charge drop precipitously at those speeds and the overall efficiency may be better in HV mode. At 40mph, it's probably ok to stay with EV. I'd say smooth acceleration and anticipatory braking (or at least gliding as long as you can) goes a long way (pun intended) in extending the EV range.
Here is the first description of it: Prime may start ICE in EV mode if Windshield Defogger switched on | PriusChat I was surprised by this last winter. Bob Wilson
The manual says it does, but I've tried it several times and it never did. Must require certain environmental factors as well.
Thanks to the dogs running out the back door, I just tried it and got the same result. The A/C compressor came on but not the engine. The ambient was ~75F but the time it did was back in February and closer to 35-40F. Bob Wilson
Not surprising at all. When I had a Volt just starting the car when it was below about 35 degrees triggered the engine for a few minutes. There was a setting I could alter that lowered that threshold to about 15 degrees. I didn't mind that much because engine heat was much more efficient than the battery anyway.
