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Engineer shares how to build an electric vehicle from the ground up -- Part 1: Designchoices

Frustrated by fast-rising gasoline prices, John antini, vice president of engineering at !D" Power,

decided to turn his creativity and problem-solving s#ills toward developing his own electricvehicle$

By Steve Taranovich, Contributing editor -- EDN, July 6, 2011

Editor's note:In part 1 of this two-part series, we look at the core technology and design choices behind this electric

vehicle. In part 2, we will discuss some mechanical and structural challenges and solutions, the specifications, road testresults, and what will be next in improvements for this amazing !" effort.

Electric vehicles (EV) and hybrid electric vehicles (HEV) are advancing rapidly. We see a parade of solutions including the

Toyota Prius (the number-one-selling hybrid) !ord !usion "ith #$-mpg city mileage %hevy Volt "ith &'-mile stretches of

all-electric driving and the issan eaf as the first affordable mainstream all-electric five-passenger car.

o" let me introduce you to yet another EV---the $*++ Pontiac !iero ,donor car., in truth only the front suspension

and steering gear "ere used from the Pontiac donor car that has gro"n into /ohn / 0antini1s ground-up design.

0antini is the vice president of engineering at T23 Po"er in Hac4ettsto"n / a company that has been in the po"erconversion industry for more than '5 years and has been providing po"er e6uipment in mobile hybrid and electrical

vehicle applications for more than 7' years.

!rustrated by fast-rising gasoline prices 0antini decided to turn his creativity and problem-solving s4ills to"ard developing

his o"n EV.

!he goal

While 0antini1s original goal "as to build a plug-in hybrid vehicle the fast-falling cost of lithium-ion (i-ion) batteries spurred

the decision to"ard the end of the pro8ect to postpone the engine9generator and to add some "eight bac4 in as additional

lithium ion batteries. :s a result the current vehicle is all-electric although the space remains to add an engine-generator

in the future. 2oing so "ill increase the cruising range of the vehicle "ell beyond the *5-mile range of the current system.

The total vehicle "eight "ith batteries is no" 75'5 lbs.

!he pro%ect

The pro8ect is a light"eight t"o-seat commuter car. The frame is a space-frame design inspired by the ocost pro8ect cars

and similar construction vehicles. 0ome bac4ground; : ocost is an economical home built ,clubman, style sports car

based on the concept of the original otus

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!igure $; T231s Bercury battery charging converter. T"o are used in series "ith battery center-tap.

0o at #.&4W the !D" 'ercury battery chargersperform a typical bul4 charge in less than one hour and there is plenty of

time to soa4 up a full charge during the day. The original chargers "ere only $.74W Bercury units that charged at &5:.

%harging used to ta4e all day at "or4 as four hours "ere 8ust needed to 8ust ,top off, the battery.

0antini has also added a ne" circuit that detects battery current greater than C5: and turns the bra4e lights on. The

regenerative bra4ing is turned up pretty high so "hen you fully bac4 off the gas pedal the bra4ing is pretty strong. 0antini

rarely uses the hydraulic bra4e system so he has noticed some surprised drivers very close to his car1s rear endD

Plans are afoot to lo"er this to &5: so the t"in rear bra4e lights and rear "indo" bra4e lights go on under most all

regenerative bra4ing conditions---this is merely a modification of the threshold to an on-board comparator. He has also

converted his tail lights to E2 to be fast-acting brighter and to use less energy. 0ee !igure 7.

http://www.edn.com/common/jumplink.php?target=http%3A%2F%2Fwww.tdipower.com%2FPRODUCTS%2Facdcpowermodules.htmlhttp://www.edn.com/common/jumplink.php?target=http%3A%2F%2Fwww.tdipower.com%2FPRODUCTS%2Facdcpowermodules.html

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!igure 7; !ast-acting E2 bra4e lights are bright and energy efficient.

The mechanical bra4ing system in this car should last beyond $'5555 miles because they are mostly used "hen at a stop

sign or traffic light on an incline after regenerative bra4ing has ta4en effect to stop any rolling.

() motor

The :% motor from %urtis 3nstruments is rated at $+.< 4W almost as much po"er as the old E motor 0antini had in his

Electric %orvette design bac4 in $*

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() motor controller

The %urtis :% motor controller is a ne" model that "or4s "ell "ith a *CV nominal battery pac4. 3t has all the features

needed for a complete vehicle controller including regenerative bra4ing. 3t is rated at C5 4W (+5 hp) "ith this battery9motor

combination. The finned heat sin4 has ducted air through it from the body-side air inta4e in this all-air cooled vehicle. 0ee

!igure #.

!igure #; %urtis :% motor controller "hich gives +5 hp "ith the battery9motor combination.

Continue reading: Lead-acid vs lithium-ion batteries

*ead-acid vs lithium-ion batteries

The original batteries "ere lead acid "eighing in at +55 lbs. Ho"ever over the three-year span of the pro8ect the cost of i-ion batteriesdropped in half and their cycle life doubled. The ne" &'5-lb i-ion batteries are from Thunder 04y. Thirty 755:H cells form a $55V755:h pac4 (75 4Wh) "hich gives around *5 miles rangeD

0antini does not have a battery balancing circuit right no" but the cells stay in balance pretty "ell "hen ne". 0tay tuned for the ne@tsteps for further improvements. 0ee !igure '.

http://www.edn.com/article/518721-Engineer_shares_how_to_build_an_electric_vehicle_from_the_ground_up_Part_1_Lead_acid_vs_Lithium_ion_batteries.phphttp://www.edn.com/article/518721-Engineer_shares_how_to_build_an_electric_vehicle_from_the_ground_up_Part_1_Lead_acid_vs_Lithium_ion_batteries.php

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!igure C; ithium-ion battery advantages---lighter smaller high energy density. (%ourtesy of Bicro Po"er Electronics)

: lead-acid discharge curve is sho"n in !igure < and a lithium ion in !igure +.

!igure

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!igure +; ithium batteries have a fairly flat discharge curve "ith sharp shoulders. 0tate of charge (F-a@is) vs batteryvoltage (=-a@is). (%ourtesy of Ener2el)

+ow it drives

0antini allo"ed me drive the car so that 3 could convey to !/01s audience the feel of an EV and describe the differences from a gasolineengine vehicle.

When 3 started up the vehicle "ith the 4ey 3 e@pected to hear the engine ,cran4ing, noise as heard in a gasoline engine and starter butthere "as only silence. The dashboard lights came on and the panel meters came to life.

!inally "hen 3 put the vehicle in reverse to bac4 out of the par4ing space the ,!or"ard9>everse, stic4 "as on the center console as 3e@pected but 0antini e@plained that this "as only for familiarity to the driver. He originally had planned to put a toggle s"itch or similardevice on the dash board panel since that is all the :% motor controller needs to reverse the motor direction----no transmission in thisvehicleD

Gecause the vehicle is belt driven by an :% motor the only sound "hen driving is the "hine of the drive belt. This sound begins todissipate at high speeds. The top speed is