A lot of tech­nol­ogy goes into elec­tric cars

Winnipeg Free Press - Section E - - AUTOS -

WHILE most of us have a gen­eral sense of what a hy­brid/elec­tric ve­hi­cle is and how it gets power ei­ther from an in­ter­nal com­bus­tion engine or elec­tric mo­tors and a bat­tery pack, there’s a lot more tech­nol­ogy that con­trib­utes to the op­er­a­tion of a hy­brid ve­hi­cle.

Let’s see what it re­ally takes to make a hy­brid ve­hi­cle op­er­ate.

It starts with the bat­tery pack — no pun in­tended. Cur­rent state-of-the-art tech­nol­ogy uses lithium ion cells to pro­duce the elec­tri­cal cur­rent. They are smaller, more ef­fi­cient and can be pack­aged in bet­ter shapes than the nickel metal hy­dride bat­ter­ies used pre­vi­ously. Lithium ion bat­ter­ies are also used in lap­tops, cell­phones and some por­ta­ble power tools, but these are dif­fer­ent than the bat­ter­ies used in au­to­mo­biles.

There are hun­dreds of for­mu­las for con­struct­ing a lithium ion cell, and the bat­ter­ies built for au­to­mo­biles have to with­stand wide tem­per­a­ture vari­a­tions, se­vere im­pacts and vi­bra­tion, be safe un­der all con­di­tions and still have a long life. This is one area we will see huge im­prove­ments in the fu­ture.

To have a long bat­tery life, the state of charge must be care­fully con­trolled. Com­put­ers mon­i­tor the bat­tery volt­age, cur­rent and tem­per­a­ture. Fans can be turned on to cool the bat­tery and some use engine coolant or elec­tric heaters to warm the bat­tery in cold weather. Bat­tery charge is typ­i­cally main­tained be­tween 20 and 80 per cent. Try­ing to charge the bat­tery more than about 80 per cent gen­er­ates more heat, which short­ens bat­tery life.

Aux­il­iary sys­tems, such as steer­ing, cli­mate con­trol and brakes, are dif­fer­ent on hy­brid ve­hi­cles. The hy­brid sys­tem will turn off the in­ter­nal com­bus­tion en- gine un­der spe­cific con­di­tions to save fuel. Sys­tems nor­mally driven by the engine, such as power-steer­ing pumps, would no longer be ef­fec­tive, so elec­tric sys­tems are used in­stead. Elec­tric power steer­ing is used on many con­ven­tional ve­hi­cles now, too, for its fu­el­sav­ing ca­pa­bil­ity.

Au­to­matic trans­mis­sions need oil pres­sure to stay in gear when the engine is stopped. Con­ven­tional au­to­mat­ics use an engine-driven oil pump. Hy­brids may add an elec­tric pump that turns on when the engine stops. Some hy­brids use an elec­tric CVT trans­mis­sion.

To pre­vent the ve­hi­cle from rolling back­ward on a hill when the driver re­leases the brake pedal, the brake sys­tems may have a “hill hold” fea­ture that keeps the brakes ap­plied for a cou­ple of sec­onds as the driver moves their foot to the ac­cel­er­a­tor pedal. For reg­u­lar driv­ing, some sys­tems use an elec­tric vac­uum pump to pro­vide vac­uum for power brake-sys­tem op­er­a­tion, while other man­u­fac­tur­ers use elec­tric/hy­draulic sys­tems to pro­vide power brake op­er­a­tion.

We like our air con­di­tion­ing, so the A/C com­pres­sor, which was pre­vi­ously belt-driven, now is pow­ered by an in­ter­nal elec­tric mo­tor. Some, such as Honda, use a com­bi­na­tion drive, ei­ther belt-driven or elec­tric-driv- en, de­pend­ing on oper­at­ing con­di­tions.

With all these “aux­il­iary” sys­tems us­ing elec­tric­ity, there needs to be a con­troller that can man­age them. The hy­brid sys­tem com­puter will also op­er­ate an in­verter, which changes volt­ages from al­ter­nat­ing cur­rent (AC) to di­rect cur­rent (DC) and back again. The elec­tric mo­tors that drive the ve­hi­cle may op­er­ate on 280 to 600 volts AC. Other sys­tems can op­er­ate on 42 volts and the lights, gauges and en­ter­tain­ment sys­tems will typ­i­cally still op­er­ate on 12 volts DC.

The in­verter cre­ates a lot of heat, so some sys­tems use coolant to keep the tem­per­a­tures un­der con­trol. Elec­tric pumps, a sep­a­rate ra­di­a­tor, over­flow tank and hoses are of­ten used to pro­vide cool­ing for the in­verter.

Plug-in hy­brids are de­signed to op­er­ate more on elec­tric power, so they have a big­ger bat­tery ca­pac­ity and longer range on bat­tery power alone be­fore the in­ter­nal com­bus­tion engine starts up. Elec­tric ve­hi­cles are also plugged in and have a range lim­ited by the bat­tery ca­pac­ity. While these ve­hi­cles do use an ex­ter­nal “charg­ing sta­tion,” they also have an in­ter­nal charger that con­verts the AC power from your home wiring to DC power to charge the ve­hi­cle’s bat­tery.

One more item you may not have thought about is a heater. Elec­tric ve­hi­cles may use elec­tric heaters for pas­sen­ger com­fort, and so may some plug-in hy­brids. Us­ing the in­ter­nal com­bus­tion engine to pro­duce pas­sen­ger com­part­ment heat is the eas­i­est way, so look for more ex­haust sys­tem-to-engine coolant heat-ex­chang­ers to warm both the engine and the pas­sen­ger com­part­ment up quickly when you ini­tially start the ve­hi­cle. Jim Kerr is an ex­pe­ri­enced me­chanic, in­struc­tor of au­to­mo­tive tech­nol­ogy, free­lance jour­nal­ist and mem­ber of

the Au­to­mo­bile Jour­nal­ists’ As­so­ci­a­tion of Canada.

A mockup of Ford’s front-wheel-drive hy­brid trans­mis

sion is dis­played at a Michi­gan plant.

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