What Is A DC-DC CONVERTER

Hybrids And EV In America



Over 3,000,000 hybrids and 250,000 plug-in cars have been sold in the United States since December 1999. You will need to get ready to sell the parts off these high tech, gas / electric autos and SUVs. Maybe you have taken a hybrid class, maybe not, but one thing is for sure, hybrids and electric cars are here to stay. At ACDC (Automotive Career Development Center) we call them EMVs (that includes hybrids, plug-in hybrids and electric cars). Learning about EMVs is exciting stuff, instructing classes around the country and the world always leaves techs saying, “Wow that is really cool how those things work!” Two of my students recently bought a hybrid for themselves. These wonders of technology gas/electric vehicles are advancing the technology battle and that is good for the environment and the customer. Now diesel/hybrids are for sale overseas.

Some nomenclature: IMA (Integrated Motor Assist) is Honda’s name for its hybrid system, THS (Toyota Hybrid System) is code for the ’01 - ’03 Prius (pronounced Pree-us). Hybrid Synergy Drive is all the Toyota hybrid systems since 2004. 2 Mode is a General Motors (GM) hybrid and BAS is a 36-volt GM micro system. ICE equals internal combustion engine, MG equals electric motor, Ni-MH equals nickel metal hydride, as in high voltage battery and many more new words for a new world.

Let’s explain more about one of the new parts under the hood (or behind the back seat), the DC-DC converter. A word of caution - high voltage is contained in a DC-DC converter and proper safety procedures must be followed to avoid injury or death.

 

DC-DC Converters

When you shut down the ICE on a hybrid at every stop sign or red light how do you keep the alternator spinning? We still need a constant 12-volt source don’t we? That little 12-volt battery has a larger brother that helps out not only when the ICE is off, but anytime the big battery is hooked up to the DC-DC converter (converter for short). It is the high voltage (HV) battery pack that supplies the 12-volt system with power, but at a much lower voltage (lv). In between the HV and lv is a step down converter known as the DC-DC converter. The converter acts like the alternator in that it supplies the 12-volt system its power and charges the 12-volt battery. The traditional 12v alternator is not fitted to a hybrid. (One exception, maybe the only, is the first generation Mercedes-Benz S400 Hybrid). The converter gets its power from the HV battery pack. The HV battery pack is not always connected to the converter so there are times when the car is using the 12-volt battery such as when the key is in the accessory position. Converters can produce any dc voltage supply needed, but hybrid vehicles must have one that makes 14 volts.

In order to keep the tech safe the converter takes in HV DC and then inverts it to ac first and then the ac power in reduced in voltage through induction (much like an ignition coil in reverse) back to a much lower ac voltage. Then the lower ac voltage is inverted into DC power at the lower voltage. If something goes wrong there is no direct connection from HV to the lower voltage. That can be done with coils of wire that transfer electrical energy without a direct connection. Even though some inversion is done we call this device a DC-DC converter. Other than testing power, grounds, inputs and outputs, this will be serviced and replaced much as you do an ECU. Honda and Ford sell it separately but most Toyota and Lexus models sell it as part of a much larger assembly known as the inverter assembly.

 

What To Tell Your Customers

“Make sure the 12 volt battery is in great shape before installing a converter” is the quote. Way it as often as you need to or you will have comebacks. How are these DC-DC converters holding up? Think back to what you know about 12-volt batteries, starters and alternators. Remember that a bad 12-volt battery left in the car can cause a premature death to an alternator. Well guess what can kill a DC-DC converter? You guessed it, a defective 12-volt battery will put a strain on the converter and it may fail. I provide hybrid tech support as part of my job and I have seen a problem with air cooled converters that relate to older hybrids and chemically worn out 12-volt batteries. Some converters are liquid cooled and these seem to be holding up better.

One way to learn more about EMVs is to get training. ACDC offers books, live and recorded webinars, live, in-person training and trade shows. The EMVs that ACDC studies are Ford, GM, Chrysler, BMW, Mercedes-Benz, Volkswagen, Porsche, Toyota, Lexus, Honda, Acura, Audi, Hyundai, Kia, Tesla, Nissan, Infiniti and more. Call 800-939-7909, email Craig@fixhybrid.com or visit www.fixhybrid.com.

Craig Van Batenburg is the CEO of ACDC and a former repair shop owner. He is engaged full time in the understanding of the technology used in hybrid and electric cars. His 45 years of automotive experience serves him well. Driving a Nissan Leaf when he can and a Chevy Volt for longer trips these days, he also owns and drives HEVs from Ford, Honda and Toyota as well a Nissan and GM. With great passion, a keen wit and more experience that most, Craig can help you understand not only how but why these new electrified cars operate the way they do  Craig is in demand worldwide and travels often to help those seeking a simple explanation of a complicated subject.

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