Re: [EVDL] EV driver's ed: accelerating for max. range vs. best time
Hello Darin,
Here is a formula that you can find what the mph is at the rpm of a motor at
different overall ratios (transmission ratios times axle ratio) using
different Wheel circumference (WC).
To find the WC, put at mark on the wheel and floor and rotate the wheel one
turn and then measure between the marks. This is normally call the rolling
distance.
RPM x WC
MPH = -----------
RATIO x 1056
or converted to
MPH x RATIO x 1056
RPM = ------------------
WC
By experimentation and testing it takes about 600 wt/hr of energy to move
100 lbs of weight at about 3000 rpm with a overall ratio of 1:1. As the
weight increases, the wt/hr increases as the ratio increases the wt/hr
decreases.
According to NetGain, A 9 inch motor has the best efficiency and torque at
about 3000 rpm. A 11 inch motor is best at 1800 rpm at the same torque
which is call the sweet spot of a motor.
To find out the best rpm in each gear, drive the EV in that one gear and
record rpm, mph, battery ampere, battery voltage and if you can the motor
ampere and motor voltage. Repeat this test in each gear.
There will be certain rpm that the ampere will stable or even drop.
I am now running a temporary Warp 9 while my 11 is maintenance and being
modified. My 9 has to run at a higher rpm then the 11 for the same torque
which the sweet spot is at about 3000 rpm. The motor ampere lowers about 50
amps at 3000 rpm as compare to the 11 at 1800 rpm while I am in a first gear
overall ration of 19.496:1 which is twice the ratios over the standard.
Roland
----- Original Message -----
From: "Darin at- forkenswift.com" <[email protected]>
To: <[email protected]>
Sent: Monday, October 15, 2007 8:42 AM
Subject: [EVDL] EV driver's ed: accelerating for max. range vs. best time
>
> I'm not too proud to admit I don't know what I don't know. With that in
> mind, I'd appreciate any pointers about general EV-specific driving
> techniques. Starting with the basics of acceleration, please let me know
> if
> I've got this wrong:
>
> Acceleration (for absolute max. efficiency/range):
>
> - keep battery amps as low as possible (ie. proverbial egg under the foot)
> - use all the gears (ie. 1st to 2nd to 3rd)
> - permit the motor to rev up high in each gear before upshifting (ie.
> 3000-5000 RPM)
>
> Acceleration (for quickest rate thereof):
>
> - maximize amp draw, but ensure voltage stays above 1.75v per cell
> - upshift when amps start dropping in each gear (ie. upshift *sooner* than
> in efficiency mode)
> - possibly start out in 2nd, vs. shifting 1st to 2nd?
>
> Once at speed, I assume the best choice is to go for most efficiency - ie.
> choose a gear that permits the motor to spin in the neighbourhood of
> 3000-5000 RPM.
>
> Keep in mind this is a 48vdc car (e.g. 5000 RPM is more or less
> unattainable
> except going downhill). I'm not sure if techniques differ depending on
> power availability (ie. staying in one gear in a high-powered EV with a
> free-revving motor).
>
> thanks for any feedback -
> Darin
> --
> View this message in context:
> http://www.nabble.com/EV-driver%27s-ed%3A-accelerating-for-max.-range-vs.-best-time-tf4627983s25542.html#a13214218
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Hello Darin,
Here is a formula that you can find what the mph is at the rpm of a motor at
different overall ratios (transmission ratios times axle ratio) using
different Wheel circumference (WC).
To find the WC, put at mark on the wheel and floor and rotate the wheel one
turn and then measure between the marks. This is normally call the rolling
distance.
RPM x WC
MPH = -----------
RATIO x 1056
or converted to
MPH x RATIO x 1056
RPM = ------------------
WC
By experimentation and testing it takes about 600 wt/hr of energy to move
100 lbs of weight at about 3000 rpm with a overall ratio of 1:1. As the
weight increases, the wt/hr increases as the ratio increases the wt/hr
decreases.
According to NetGain, A 9 inch motor has the best efficiency and torque at
about 3000 rpm. A 11 inch motor is best at 1800 rpm at the same torque
which is call the sweet spot of a motor.
To find out the best rpm in each gear, drive the EV in that one gear and
record rpm, mph, battery ampere, battery voltage and if you can the motor
ampere and motor voltage. Repeat this test in each gear.
There will be certain rpm that the ampere will stable or even drop.
I am now running a temporary Warp 9 while my 11 is maintenance and being
modified. My 9 has to run at a higher rpm then the 11 for the same torque
which the sweet spot is at about 3000 rpm. The motor ampere lowers about 50
amps at 3000 rpm as compare to the 11 at 1800 rpm while I am in a first gear
overall ration of 19.496:1 which is twice the ratios over the standard.
Roland
----- Original Message -----
From: "Darin at- forkenswift.com" <[email protected]>
To: <[email protected]>
Sent: Monday, October 15, 2007 8:42 AM
Subject: [EVDL] EV driver's ed: accelerating for max. range vs. best time
>
> I'm not too proud to admit I don't know what I don't know. With that in
> mind, I'd appreciate any pointers about general EV-specific driving
> techniques. Starting with the basics of acceleration, please let me know
> if
> I've got this wrong:
>
> Acceleration (for absolute max. efficiency/range):
>
> - keep battery amps as low as possible (ie. proverbial egg under the foot)
> - use all the gears (ie. 1st to 2nd to 3rd)
> - permit the motor to rev up high in each gear before upshifting (ie.
> 3000-5000 RPM)
>
> Acceleration (for quickest rate thereof):
>
> - maximize amp draw, but ensure voltage stays above 1.75v per cell
> - upshift when amps start dropping in each gear (ie. upshift *sooner* than
> in efficiency mode)
> - possibly start out in 2nd, vs. shifting 1st to 2nd?
>
> Once at speed, I assume the best choice is to go for most efficiency - ie.
> choose a gear that permits the motor to spin in the neighbourhood of
> 3000-5000 RPM.
>
> Keep in mind this is a 48vdc car (e.g. 5000 RPM is more or less
> unattainable
> except going downhill). I'm not sure if techniques differ depending on
> power availability (ie. staying in one gear in a high-powered EV with a
> free-revving motor).
>
> thanks for any feedback -
> Darin
> --
> View this message in context:
> http://www.nabble.com/EV-driver%27s-ed%3A-accelerating-for-max.-range-vs.-best-time-tf4627983s25542.html#a13214218
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev