range vs. "jackrabbit starts"

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Nubo

Well-known member
Joined
May 28, 2010
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Location
Vallejo, CA
In terms of EV driving efficiency, is there a serious penalty to quick acceleration? For an ICE, jackrabbit starts are a classic way to waste gas. But that's due to the physical nature of the engine. There's nothing inefficient about acceleration per-se. Will an EV experience significant range loss if you accelerate briskly?
 
Accelerate faster for a shorter time, in theory, except for losses, is basically the same energy.

Being at a higher speed longer would use a little more energy, due to things like aerodynamic losses.

However, the bigger issue involves drawing higher currents from the battery cells. Since there is a cell "resistance" (manifested as a lowered cell voltage when current is drawn from the cell), one gets less energy from the cell when drawing at higher currents.

In drawing 100 amp-hours at low currents, the "average" cell voltage might be "3.5" (providing 350 watt-hours of energy), but at higher currents, the voltage might be only "2.5" (providing only 250 watt-hours of energy).

So, yes, depending upon battery cell chemistry, temperature, etc., there IS a penalty for fast acceleration in a typical EV.
 
Gary is right, there is a big penalty, simply because of the high drain you put on the batteries. Drive quickly, accelerating quickly every time you can is a sure-fire way to drain the batteries quicker. Drive like a lunatic and you can halve the range of an electric car - in just the same way as you can halve the fuel economy of a regular gas car by hard driving.
 
I ride a Vectrix EV Maxi-Scooter. It is capable of a range of about 60 miles. That is with minimal stops&starts and staying under 45 mph. When driving quicker and faster, that range goes down to about 20 miles, a very notable decrease. It uses NiMH batteries.
 
In my lithium powered bike, the batteries stay cool and can dish out much more than the motor and controller can take so they aren't the limiting factor the way a lead-acid battery would be.

In my case, jackrabbit starts generates a LOT more heat in the motor and controller - I suspect that's where the hard-driving losses will appear in a modern vehicle using relatively low resistance batteries.
 
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