Step on it! Have some fun.

There is a misconception in various posts lately regarding rapid acceleration in EV mode. The commonly held belief that it significantly reduces your EV range is incorrect. Feel free to step on it, and accelerate to your heart's content. Your range will not be significantly reduced, and could, in fact, end up being greater than using a technique of very slow acceleration. Here's why:

• Electric motors experience very little change in efficiency as torque increases from roughly 25% to near maximum, in fact most maximize efficiency near 50%. I could not find any specific information about the Prius motor/generators (gurus please chime in if you have any), but note the flat efficiency curves on these two examples of vehicle motors:

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Note the inefficiency below roughly 25% - a range one might consider avoiding if one wishes to get the most power out of each amp supplied by the battery.​

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• What about the falloff of amp-hours at higher discharge rates? Don't worry about it. It is not a factor with Lithium Ion batteries. That concern died with the use of Lead-Acid batteries to power EVs, shown as "AGM" in this chart:

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I live in a community of 35,000, with 10,000 registered electric vehicles (that's right - 1 for every 3.5 residents), and a legacy of using them on a daily basis to get around town for the past 53 years. I am immersed in an EV culture. Part of that culture has been to avoid extremely slow acceleration in order to maximize range, so this is not a new idea - just one that needs to make its way from the cart paths to the streets.

Of course your range will suffer at high speeds, but is affected very little by how quickly you accelerate to get there. Step on it, and go have some fun.

 

As terrain and winds affect speed, I would be more interested in learning what the most efficient power level would be, and how we mere mortals might be able to discern such from the HSI in EV mode. While the efficiency curve is nearly flat, it is not completely flat. There is a peak efficiency power point, but without a graph of the PiP's actual efficiency curve, and some information from Toyota (or one of our well-connected gurus) as to how this peak correlates with our HSI display, we are flying blind.

Making a newb's sucker assumption of 1 for 1 correlation, I currently avoid the the bottom 25% of the display completely and use 75-90% of HSI displayed power for accelerating to the speed limit, then generally use the cruise control to maintain it. The cruise control does a magnificent job of managing energy in EV mode, by the way. It allows the speed to fall off a bit during a steep climb in order to prevent the ICE from kicking on, and I have never seen it exceed max regen on descents.

Some doubters, which is understandable. We've lived most of our lives driving vehicles that spit out more waste than power when we've stomped on the "Go" button. It is difficult to change our way of thinking.

I have a 10.7 mile closed loop errand route that I have repeated many, many times (gotta start and end any test scenario at the same place in order to cancel out the effect of winds and terrain). I do it with the air conditioning and audio system blasting at the same level, so total loads are essentially the same. Driving the loop conservatively and agressively and getting back to the garage within .3 miles of range remaining at either extreme prompted me into researching this post in the first place. Try it yourself to prove it to yourself. Just be fair, and make it a closed loop, replicating air conditioning and other power draws.

 

John,

The last thing I want to accomplish on this forum is to disrespect a guru-level gentleman that I have learned immensely from, so please do not treat the following as a challenge to your wisdom. Nor do I wish to disagree with you, as you are absolutely correct, but for reasons of which you might not be aware.

This post deals with operation of the PiP in EV mode only. In other words, as solely an electric vehicle, a golf cart, a Leaf. I'm talking about only the rarified air of sweet EV performance. It is a range of potential electrical power that exceeds that of the Gen III "regular model" by a factor of roughly 20. My invitation for PiP owners to submit data points extends to those that can complete closed-loop courses of less than 11 miles (or 12 miles with the air conditioning off) using EV only (ICE off for the entire loop) at speeds up to 62mph, not to "regular model" owners that can accomplish the same up to something less than a mile at parking lot speeds. The brisk acceleration of which I speak is recommended to be carried out in EV mode only (ICE off), as opposed to the brisk HV mode acceleration (ICE on and operating at its most effiicient output level) that your previous and immensely informative posts have been utilized by all of us to improve the effeciency of our magnificent Prii in HV mode.

To borrow the words of a cunning linguist... "No disrespect"

 

I cannot credibly recommend any power level without examining Toyota's efficiency curves and getting some reliable intel on mapping of those curves to the HSI display.

As I revealed in a previous post, I'm a dumb-nice person newb and assume a 1:1 mapping of the efficiency curve, and further reveal my ignorance by assuming a 1:1 mapping of that curve to the HSI display. Utilizing both faulty assumptions, I accelerate at 75%-90% of the HSI - more out of fear of triggering the ICE than seeking the most efficient acceleration profile.

 

Too true. In this case it was my misconception reguarding your post. Glad to see we are on the same page.