Comments on: How much (electric) power is needed? http://blog.autospeed.com/2008/01/08/how-much-electric-power-is-needed/ AutoSpeed's Blog. Opinion and Auto News Comment Thu, 19 Jan 2012 10:07:00 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Ben http://blog.autospeed.com/2008/01/08/how-much-electric-power-is-needed/comment-page-1/#comment-95161 Ben Mon, 05 Oct 2009 22:50:38 +0000 http://blog.autospeed.com/2007/01/08/how-much-electric-power-is-needed/#comment-95161 that only applies if the peak speed of the motor is the same as the peak speed of the wheels (ie whatever wheel rpm equate to 130km/h). If it is higher or lower you get either less available power or a lower speed. Then you also have to realise that a motor capable of directly driving a wheel is going to be quite large and heavy (simply because of the sheer torque it has to generate). Smaller motors capable of higher rpm (but less torque) through a gearbox are a lighter solution. that only applies if the peak speed of the motor is the same as the peak speed of the wheels (ie whatever wheel rpm equate to 130km/h). If it is higher or lower you get either less available power or a lower speed.

Then you also have to realise that a motor capable of directly driving a wheel is going to be quite large and heavy (simply because of the sheer torque it has to generate). Smaller motors capable of higher rpm (but less torque) through a gearbox are a lighter solution.

]]> By: Eric http://blog.autospeed.com/2008/01/08/how-much-electric-power-is-needed/comment-page-1/#comment-93866 Eric Fri, 18 Sep 2009 16:49:48 +0000 http://blog.autospeed.com/2007/01/08/how-much-electric-power-is-needed/#comment-93866 Hi Julian. Mating electric motors to ICE transmissions is not a good idea. I believe the best way is get rid of the trans and hook the motor directly to the wheels. You would get better performance. A 30kw motor with a peak of 60Kw is adequate. Hi Julian. Mating electric motors to ICE transmissions is not a good idea. I believe the best way is get rid of the trans and hook the motor directly to the wheels. You would get better performance. A 30kw motor with a peak of 60Kw is adequate.

]]> By: Paul http://blog.autospeed.com/2008/01/08/how-much-electric-power-is-needed/comment-page-1/#comment-40715 Paul Thu, 30 Oct 2008 00:41:29 +0000 http://blog.autospeed.com/2007/01/08/how-much-electric-power-is-needed/#comment-40715 It's a pretty well known number really. 200wh/mi Most AC EVs use around 200wh/mi. (approx 125wh/km) That's the figure given for the GM Volt, Wrightspeed X1 and a numer of others. The tzero uses around 155wh/mi. So @ $0.10 per kw/hr you'll get 5km range. Comparing the per mi/km cost to an ICE gives you 1/20th and beyond. This doesn't apply to brushed DC as they do not have regen. What's even more mind blowing is how little power something like the Killacycle uses in a 1/4 mile run. It has 500hp, does an ET of 8 seconds and uses $0.07 worth of electricity per run including the burnout and the drive back to the pits. The truth is 8 seconds is only 1/450th of an hour so the faster it goes the less it costs (well.... almost) LOL It’s a pretty well known number really. 200wh/mi

Most AC EVs use around 200wh/mi. (approx 125wh/km) That’s the figure given for the GM Volt, Wrightspeed X1 and a numer of others. The tzero uses around 155wh/mi. So @ $0.10 per kw/hr you’ll get 5km range. Comparing the per mi/km cost to an ICE gives you 1/20th and beyond. This doesn’t apply to brushed DC as they do not have regen.

What’s even more mind blowing is how little power something like the Killacycle uses in a 1/4 mile run. It has 500hp, does an ET of 8 seconds and uses $0.07 worth of electricity per run including the burnout and the drive back to the pits. The truth is 8 seconds is only 1/450th of an hour so the faster it goes the less it costs (well…. almost) LOL

]]> By: Adam Dunstone http://blog.autospeed.com/2008/01/08/how-much-electric-power-is-needed/comment-page-1/#comment-31317 Adam Dunstone Thu, 17 Jul 2008 00:04:21 +0000 http://blog.autospeed.com/2007/01/08/how-much-electric-power-is-needed/#comment-31317 My opologie's Jake miss read your statement ! agree with your 0.2kwh/km statement assuming motor draws 20kw power! very sorry to tired to read properly need some sleep i think! My opologie’s Jake miss read your statement ! agree with your 0.2kwh/km statement assuming motor draws 20kw power! very sorry to tired to read properly need some sleep i think!

]]> By: Adam Dunstone http://blog.autospeed.com/2008/01/08/how-much-electric-power-is-needed/comment-page-1/#comment-31316 Adam Dunstone Thu, 17 Jul 2008 00:00:55 +0000 http://blog.autospeed.com/2007/01/08/how-much-electric-power-is-needed/#comment-31316 Sorry to say, jake you got you got it backwards mate! 20kw for an hour is 20kw/h not 0.2 kw/h big difference, power divided by time not speed gives watt hours! Also If Motor is suplying 20kw actual output power, it will use more electrical energy than this prob in the order of 23kw! Sorry to say, jake you got you got it backwards mate! 20kw for an hour is 20kw/h not 0.2 kw/h big difference, power divided by time not speed gives watt hours! Also If Motor is suplying 20kw actual output power, it will use more electrical energy than this prob in the order of 23kw!

]]> By: jake c http://blog.autospeed.com/2008/01/08/how-much-electric-power-is-needed/comment-page-1/#comment-31221 jake c Tue, 15 Jul 2008 06:22:02 +0000 http://blog.autospeed.com/2007/01/08/how-much-electric-power-is-needed/#comment-31221 fred, assuming your motor is supplying 20kw of power at 100kph, for one hour, then it is simply 20/100 = 0.2kWh/km fred, assuming your motor is supplying 20kw of power at 100kph, for one hour, then it is simply 20/100 = 0.2kWh/km

]]> By: Adam Dunstone http://blog.autospeed.com/2008/01/08/how-much-electric-power-is-needed/comment-page-1/#comment-31218 Adam Dunstone Tue, 15 Jul 2008 05:21:45 +0000 http://blog.autospeed.com/2007/01/08/how-much-electric-power-is-needed/#comment-31218 Hello Fred! The 27kw/tonne figure is a good one for power output of the motor for your car but the size of your solar array will have little to do with this figure in the real world. The things you need to know are how far are you planning on going in your electric car on a regular basis and how much energy will it need for that! Things you will need to know include (if your car isn't off the shelf n have the figures handy! ha ha ) Average distance your going to travel, average speeds, power consumption at those speeds, battery effeciency at those current draws etc etc lots to work out! If your looking for a figure of some sort to guestimate stuff a VN commadore sedan uses about 12kw to cruse at 100km/h on level ground on a windless day! A different car (different wind resistance n rolling resistance ) will use more or less . So you would say 12 kw for an hour at 100km/h right would get you 100km right? sorry wrong you have to factor in your losses charging the battery for a start then losses as you use the power driving the car from large current draw etc if you assume 80% loss at both ends (very conservative) you loose alot before you even worry about hills n stuff! You will need a huge solar array or a very small car ! Look up the solar taxi that went through Aus recently for an idea of the size of array for even a very effecient (small) car. Hello Fred! The 27kw/tonne figure is a good one for power output of the motor for your car but the size of your solar array will have little to do with this figure in the real world.

The things you need to know are how far are you planning on going in your electric car on a regular basis and how much energy will it need for that!

Things you will need to know include (if your car isn’t off the shelf n have the figures handy! ha ha ) Average distance your going to travel, average speeds, power consumption at those speeds, battery effeciency at those current draws etc etc lots to work out!

If your looking for a figure of some sort to guestimate stuff a VN commadore sedan uses about 12kw to cruse at 100km/h on level ground on a windless day! A different car (different wind resistance n rolling resistance ) will use more or less . So you would say 12 kw for an hour at 100km/h right would get you 100km right? sorry wrong you have to factor in your losses charging the battery for a start then losses as you use the power driving the car from large current draw etc if you assume 80% loss at both ends (very conservative) you loose alot before you even worry about hills n stuff!

You will need a huge solar array or a very small car ! Look up the solar taxi that went through Aus recently for an idea of the size of array for even a very effecient (small) car.

]]> By: Fred http://blog.autospeed.com/2008/01/08/how-much-electric-power-is-needed/comment-page-1/#comment-31180 Fred Mon, 14 Jul 2008 17:57:52 +0000 http://blog.autospeed.com/2007/01/08/how-much-electric-power-is-needed/#comment-31180 I'm trying to figure out how many kw-hours a car uses in order to see if it makes sense for me to install solar collectors on my house to supply an electric car. The above discussion is mostly too technical for me. But, if we take the 27 kW/tonne figure as given, how would that translate into kw-hrs/kilometer? I’m trying to figure out how many kw-hours a car uses in order to see if it makes sense for me to install solar collectors on my house to supply an electric car. The above discussion is mostly too technical for me. But, if we take the 27 kW/tonne figure as given, how would that translate into kw-hrs/kilometer?

]]> By: hugo http://blog.autospeed.com/2008/01/08/how-much-electric-power-is-needed/comment-page-1/#comment-29375 hugo Thu, 05 Jun 2008 12:07:32 +0000 http://blog.autospeed.com/2007/01/08/how-much-electric-power-is-needed/#comment-29375 Julian Edgar, do you want to get rid of the 10 series Prius battery?? Hugo Julian Edgar, do you want to get rid of the 10 series Prius battery??
Hugo

]]> By: Adam Dunstone http://blog.autospeed.com/2008/01/08/how-much-electric-power-is-needed/comment-page-1/#comment-27315 Adam Dunstone Thu, 27 Mar 2008 19:44:35 +0000 http://blog.autospeed.com/2007/01/08/how-much-electric-power-is-needed/#comment-27315 Dennis motor manufactures may flaunt there 3-phase motor on their website's but you still cant get past the fact that any realworld comparison between our beloved motors comes out like this :- Permanant magnet brushless motor compared to an equaly rated continus power output induction motor of any description will result with these facts magnet:- Lower weight (by considerable amount aproximatly 50%) magnet:- higher effeciency magnet:- higher torque (given similar rotating diameter) magnet:- currently lower cost (granted will change to opostite with increase in supply of high frequency induction motors) magnet:- easy to setup regenrative braking (yes induction motor will to but more involved in electronics) Sorry to say but at the moment the only real benifit to a induction motor over a rare earth magnet brushless motor that I can see is as you point out, long life with limited loss of effeciency! Yes a rare earth magnet will loose magnetic strength over time (very quickly if over temped currenty anything over 120 deg) Permanent magnet brushless motors have taken off in many areas of the hobbie and industral world and have proven themsevels very reliable over the last 5 years in the hobbie world they are most often abused far beond their design limits (I have myself on regular occasions driven a now 4 year old motor past its rated limits by over 1000% to thermal shutdown with only modest reductions in effecency) and yes i've killed a few but all were driven far past their working limits. As far as I'm concerned the electric motor industry seems very keen on the permant magnet brushless motor also, alot of auto manufactures are using them and yes induction motors to ! So there must be benifits to both or they would all be using induction motors wouldn't they? Dennis motor manufactures may flaunt there 3-phase motor on their website’s but you still cant get past the fact that any realworld comparison between our beloved motors comes out like this

:- Permanant magnet brushless motor compared to an equaly rated continus power output induction motor of any description will result with these facts

magnet:- Lower weight (by considerable amount aproximatly 50%)
magnet:- higher effeciency
magnet:- higher torque (given similar rotating diameter)
magnet:- currently lower cost (granted will change to opostite with increase in supply of high frequency induction motors)
magnet:- easy to setup regenrative braking (yes induction motor will to but more involved in electronics)

Sorry to say but at the moment the only real benifit to a induction motor over a rare earth magnet brushless motor that I can see is as you point out, long life with limited loss of effeciency!

Yes a rare earth magnet will loose magnetic strength over time (very quickly if over temped currenty anything over 120 deg)

Permanent magnet brushless motors have taken off in many areas of the hobbie and industral world and have proven themsevels very reliable over the last 5 years in the hobbie world they are most often abused far beond their design limits (I have myself on regular occasions driven a now 4 year old motor past its rated limits by over 1000% to thermal shutdown with only modest reductions in effecency) and yes i’ve killed a few but all were driven far past their working limits.

As far as I’m concerned the electric motor industry seems very keen on the permant magnet brushless motor also, alot of auto manufactures are using them and yes induction motors to ! So there must be benifits to both or they would all be using induction motors wouldn’t they?

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