Electric Vehicle Reality Check

Lexus RX-400H Electric Hybrid SUV Overview

Lexus RX-400H: Recovering Wasted Energy

the Lexus 400H is a good example of an advanced electric vehicle

So we're cruising in 'Lexi' at about 100 kmh (60 mph) along the Parkway from Banff to Golden, and I'm seeing about 10,000 watts showing on the dashboard gauge.

That's probably the first thing you'll notice when you first sit in the cockpit of a Lexus hybrid vehicle. Instead of a tachometer, you get a watt meter that measures the overall power output of the Lexus hybrid drive system.

The Power to Push

When it comes to cars, we're used to knowing what the engine horsepower (hp) is, but watts are a unit of power as well (more often associated with electric devices). In fact, there is a direct conversion ratio:

1,000 watts (w) = 1.34 horsepower (hp)

the watt meter replaces the tachometer The Lexus 400H has a gauge that reads up to 200 kw - that's 200,000 watts, equivalent to 268 hp. But it also reads lower than zero, into the negative region, because it can regain what would normally be lost power from braking and coasting downhill, storing that normally wasted energy in the 288 volt NiMh battery that sits under the rear seat.

Everyone knows what a 100 watt light bulb looks like (although that's changing too due to the advent of LEDs), and I thought it was interesting that it takes 10,000 watts (100 light bulbs @ 100W each) of power to push this SUV along the highway at 100 kmh.

Lexi has a drag co-efficient (a measure of wind resistance) of 0.34, which is pretty streamlined for an SUV. Older brother Prius is much better at 0.26, so you certainly give up some aerodynamic efficiency for having an SUV.

The Starter Doesn't Work!

The very next thing you'll probably notice is that the starter doesn't work. When you insert the key, the first thing that happens is the steering wheel moves back into position, having moved out of the way for easy access the last time you shut her down.

At this point you can also press the L1 button on the door, which will restore the seat and mirror positions if someone else has been driving it (L2 settings). We like this feature a lot as Jenni and I have very different driving positions.

Then when you turn the key to start it as you would normally do in any other vehicle, nothing happens, except a READY light comes on in the power gauge.

My first impulse was to panic a little, thinking that I have a major problem already, but then I learn that nothing actually needs to happen! You simply put the gear lever in D and start off in great silence, running purely on battery power. This is a very eerie feeling at first, but you soon learn to like it a lot.

It is also a very different experience when you hear the gas engine shut off at a traffic light, but think of the fuel you're saving and particularly the emissions that aren't coming out of your exhaust pipe.

The Lexus 'Synergy' System

the Lexus 400H energy management systemSometimes when you start off, you will hear the gas engine start up, although it is very, very quiet. The decision to do this is made by the Lexus Synergy system, a powerful computer that controls all aspects of the energy transfer from the 4 motors. I call it 'The Decider'.

No self-respecting energy management system would be without proper instrumentation, and the Lexus system is no exception.

It has an excellent animated display that you can call up on the touch screen (assuming you have the navigation option). There is a simplified version that appears on the bottom of the speedometer, if you don't have the navigation option.

This screen is constantly changing, revealing how the Synergy system is moving energy between the 3 electric motor/generators and the gas engine, transferring power to the wheels and back to the main high voltage battery. This is very helpful for learning how to drive it to get the best gas mileage, and it's very entertaining if you are a gadget guy like me!

A second screen called the 'Consumption Monitor' analyses your overall consumption and efficiency, so that you can track your usage and maximize efficiency.

the Lexus 400H energy monitoring system These displays provide excellent, easy to understand instrumentation, considering the complexity of what is going on (the display will be in metric units on a Canadian vehicle).

If you're not into precision monitoring and just want to drive the damn thing, then relax, because it really does almost drive itself. These systems work quite flawlessly and you can barely tell when it starts and stops the gas engine.

Just turn off the display, adjust the driver's side air conditioning, put on some music to enjoy with the 11 speaker sound system, and set the cruise control for your highway speed - it will take care of itself very nicely.

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