Friday, July 25, 2008

Performance data for a GWiz in London

This article is by Kele Baker and David MacKay, based on data collected by Kele

The performance of the G-Wiz varies with driving conditions and the weather. The G-Wiz can be driven on 'high' or 'low' power. The lights may be on or off. And the efficiency of the battery appears to depend on the temperature. The graph shows data for 19 charging events: the distance travelled in miles is on the horizontal axis and the energy required from the grid to recharge the battery (measured at the socket with a Maplin meter) is on the vertical axis.

The best performance was 16 kWh per 100 km. The worst was 33 kWh per 100 km. The average was 21 kWh per 100 km. This number is roughly four times better than the energy consumption of an average petrol car doing 33 miles per gallon, which uses 80 kWh per 100 km. In money terms, the electricity cost of the G-Wiz is 2.1 pence per km (assuming 10 p per kWh).


Ray Lightning said...

The key problem of electric cars is not energy efficiency (where they are the king ) but high capital costs, non-availability of recharge stations and low peak power.

I hope the car manufacturers tackle these problems soon. An obvious step forward would be the use of Lithium ion polymer batteries (in replacable blocks for easy swapping).

I am an Indian, and ofcourse, I would like Rewa-GWiz to do well in these areas :)

Unknown said...

According to the GWiz specs, it has equivalent of 63 g/km emissions, assuming the standard power station mix of generation types in UK. Various small cars are now down to circa 100 g/km, and these are not limited to 50 mph and round-town range. With current fuel prices, small cars will (i predict) get quite rapidly better, with diesel hybrid technology etc. I'll stick with a conventional car plus bike and public transport as much as possible!

AshleyMills said...
This comment has been removed by the author.
AshleyMills said...

The electric car scene is very interesing. The main problems are:

i) Range
ii) Battery lifetime
iii) Sex Appeal

The range and battery lifetime limitations are due to the battery technology. At the forefront of development (as in something that is actually available in the near future, rather than some pipe dream like supercapacitors) appears to be Altairnano's Nanosafe battery. They claim 25000 degredation free cycles compared to traditional li-ion batteries. (

They also claim a 70kwh capacity pack with a charge time of 10 minutes (which would need a serious charger) and a range of 250kmh (depends on car obviously).

This technology is touted to be part of the Lightning electric car ( along with the amazing Hi-Pa Drive motors (

The sex appeal of cars like the Gwiz leaves a lot to be desired for. Irrespective of what illusions of benevolence most people might have, this kind of design won't sell to the mass market. From this perspective there are some very interesting cars under development and existing already:

Lets start with The Tesla Roadster by Tesla motors (, check out these vitals:

0-60mph in 3.9 seconds
220 miles per charge
less than 2cents per mile
Sleek looks

Sound good? The problem here is the price. $98,000. Its a sports car only for the elite. Also its not very practical for most people.

One of the most promising cars appears to be the Think! OX ( which is just a concept at the moment. The company have also produced a vehicle called the Think City which is similar to the Gwiz.

Another notable coming soon car is the Mitsubishi MiEV (, this also looks like a normal car and will appeal to the masses.

Lets not forget the GM EV1 (, and the Toyota RAV4 EV (; practical electric cars that were, seemingly deliberately, discontinued and relentlessly destroyed (Although some of the RAV4 EVs managed to survive due to campaigners). These cars were both good looking and practically sized. They were somewhat range limited (approx 120 miles max), and the battery technology meant frequent replacements.

Of course, new cars are "stuff" and hence cost CO2 to produce and this must be taken into account.

AlexTangoFuego said...

Thanks David, for bringing the hard numbers and hard facts to "light". Pun intended.

NOW I know why I should have paid more attention (and made better grades) in my math & physics classes.

I look forward to more...

Unknown said...

Fancy doing a comparative test for something like the MEGA City?



David MacKay FRS said...

I'd definitely like to receive data from a MEGA city user or a TH!NK user. My guess is that the GWiz has not been optimized for efficient charging, and other electric cars might be better. It would be great to test and know.