If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #4274
Joined: Mon Dec 19 2011, 03:10AM
Location:
Posts: 47
I am in the process of designing an electric go-kart and I am running into a few problems. I probably won't end up building this due to costs, but I would like to figure out those costs before I decide I can't do this project.
I plan on using the MARS ME0909 Min-E-Tek Motor, which puts out 4hp continuous, 12.8hp peak. I have found this motor to be more than adequate for my needs as far as propulsion go. The cart will be theoretically capable of going from 0-30mph in 2.75 seconds. 6" diameter wheels, which need to rotate at 1522 RPM to go the 30mph The cart will be under 150 pounds (To go 0-30 in 2.75 seconds) Acceleration of 16ft/sec^2
My Calculations for Torque: F=MA F= 150 pounds x 16 ft/sec^2 (these numbers were converted to metric for the actual calculation) F=331.82 Newtons
Torque (nm) = Force (newtons) x Radius (meters) T=331.82 x 0.0762 (3") T=25.3 newton meters (224 inch-pounds)
The Min-E-Tek motor puts out .102nm/amp, so I need a theoretical 211A for this to work. The motor runs at 100A continuous, but peaks out at 300A for 30 minutes. I don't plan on flooring this very often or for very long, so this will be just fine.
The motor weighs 24 pounds, I weigh about 130, so now we're four pounds over. Oh well, the motor can put out 5.3 nm more than I need for 150 pounds, so I am good so far.
The real problem comes with the batteries. For weight, I will have to end up using Lithium Iron Phosphate batteries, which are expensive, light, and powerful. The motor chugs power at 4.8kw cont, or 15kw for 30 seconds, so I can't hold back on battery power. Also, the motor runs on 48v. One Thunder Sky 3.2v 90AH LiFePO4 cell is $135, and I would need 15 to achieve 3.2v. That's $2025 in batteries, not to mention that's 100 pounds. Now you see my problem.
I have been interested (not practically of course) in Braille Battery. They sell super light weight racing batteries. A 16v 60AH lithium battery weighs 7.5 pounds, and I would only need 3. Oh, wait, they're $2200 each.
I am wondering if there is any practical way to achieve my goal of this go-kart. Different layout? Different motor? Different source of batteries? Something I did wrong in my calculations? Anything to help would be awesome.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
First of all I think you should recheck your calculations, as I don't see any sign of a gear ratio. You calculate the gear ratio from the wheel RPM at your desired top speed, the motor's Kv and the battery voltage. The gear ratio then affects torque: say you step down the RPM by a factor of 3, you step the torque up by a factor of 3.
But assuming your calculations were right: If you want to achieve your 0-30 time, you just need a bigger motor. For the sake of a quick worked example, let's say you use one twice as big. Or maybe two of the original motor, one driving each rear wheel. The details don't matter right now.
Then you have twice the torque at the wheels, so the kart can be 300lbs and still meet your 0-30 spec. That leaves 150lbs for the battery pack, so you can use the Thunder Sky cells easily.
You could also settle for a lower top speed, or slower acceleration. Both would save you money of course.
Or like most vehicle makers, you could save even more money by going back to a gasoline engine.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Electric Go Kart
