Design Article
Teardown Report: Chevy Volt's electronic secrets
Rick DeMeis
5/10/2012 3:00 AM EDT
Other electronics and teardown tales
If not connected with the hybrid drive system, the rest of the Volt's electronics are fairly conventional state-of-the-automotive-art. An air-cooled DC-DC converter (with PCBs from TDK and a Renesas MCU) takes the place of an alternator to provide 12V for running standard auto systems such as doors, lights, navigation, and audio, and to charge the auxiliary 12V battery.
Taking apart the center stack uncovered a communications module PCB by LG hosting a Freescale memory controller with Spansion flash. John Scott-Thomas highlights the sparseness of these infotainment boards, noting there is much space but not all that much processing power is needed to handle these systems, thus several functions are put on single chips. Plus adequate space between the resistive touch switches on the front of the panel helps avoid the driver pressing an incorrect function.
Conclusions
As shown by the teardown, the Volt is designed with quality and attention to detail while allowing for upgrades and improvements. So as customer experience is gained, it will be interesting to see how this plug-in hybrid platform evolves—and at what rate—in the coming years.
Sidebar: Logistics of doing an automotive teardown
Munro & Associates' Al Steier says that before he begins one of the company's automotive teardowns he reads all the information available on the car that he can get his hands on. For hybrid and electric vehicles a basic step is to locate the service disconnect that "safes" the high voltage lines when removed—and then secure that in his tool box.
Pictures of components are taken before and after removal from all possible angles for documentation and as part of the effort to fathom materials and manufacturing processes. Components and their makers are determined at the circuit-board level. "Decapping" ICs and ASICs then can show memory capacity, etc. if not available from such components' published data.
Sidebar: The battery that wouldn't die
Al Steier says that the Volt was delivered for the teardown just like any other purchased from a Chevy dealer—with a full tank of gas. The teardown team left systems on to drain down the Li-ion battery before taking the car apart, but the vehicle software started the gas engine to prevent deep discharge of the battery.
It was decided to drain the tank and then leave systems (lights and radio) on again. This drained the 12V battery, which was recharged from the high-voltage system overnight—but the system software did not allow the battery to completely discharge—only to a level where the car could go an indicated 35 miles.
Finally a company specializing in electric vehicles was called upon to drain the battery using a power resistor across the terminals.
Sidebar: Differences between the Volt and Prius
Having previously taken apart a Toyota Prius hybrid for a previous teardown in 2007, here are some of the differences, and similarities, Al Steier found between it and the Chevy Volt. Keep in mind, the Prius did not have plug-in recharging capability five years ago.
For further reading:
Innovation revelation: Engineering the Chevy Volt, Automotive Designline
This story was originally published in EDN.
If not connected with the hybrid drive system, the rest of the Volt's electronics are fairly conventional state-of-the-automotive-art. An air-cooled DC-DC converter (with PCBs from TDK and a Renesas MCU) takes the place of an alternator to provide 12V for running standard auto systems such as doors, lights, navigation, and audio, and to charge the auxiliary 12V battery.
Taking apart the center stack uncovered a communications module PCB by LG hosting a Freescale memory controller with Spansion flash. John Scott-Thomas highlights the sparseness of these infotainment boards, noting there is much space but not all that much processing power is needed to handle these systems, thus several functions are put on single chips. Plus adequate space between the resistive touch switches on the front of the panel helps avoid the driver pressing an incorrect function.
Of the 18 electronic units removed in the Volt teardown, roughly three-fourths are associated with hybrid power train functions. (Courtesy Munro & Associates)
Conclusions
As shown by the teardown, the Volt is designed with quality and attention to detail while allowing for upgrades and improvements. So as customer experience is gained, it will be interesting to see how this plug-in hybrid platform evolves—and at what rate—in the coming years.
Sidebar: Logistics of doing an automotive teardown
Munro & Associates' Al Steier says that before he begins one of the company's automotive teardowns he reads all the information available on the car that he can get his hands on. For hybrid and electric vehicles a basic step is to locate the service disconnect that "safes" the high voltage lines when removed—and then secure that in his tool box.
Pictures of components are taken before and after removal from all possible angles for documentation and as part of the effort to fathom materials and manufacturing processes. Components and their makers are determined at the circuit-board level. "Decapping" ICs and ASICs then can show memory capacity, etc. if not available from such components' published data.
Sidebar: The battery that wouldn't die
Al Steier says that the Volt was delivered for the teardown just like any other purchased from a Chevy dealer—with a full tank of gas. The teardown team left systems on to drain down the Li-ion battery before taking the car apart, but the vehicle software started the gas engine to prevent deep discharge of the battery.
It was decided to drain the tank and then leave systems (lights and radio) on again. This drained the 12V battery, which was recharged from the high-voltage system overnight—but the system software did not allow the battery to completely discharge—only to a level where the car could go an indicated 35 miles.
Finally a company specializing in electric vehicles was called upon to drain the battery using a power resistor across the terminals.
Sidebar: Differences between the Volt and Prius
Having previously taken apart a Toyota Prius hybrid for a previous teardown in 2007, here are some of the differences, and similarities, Al Steier found between it and the Chevy Volt. Keep in mind, the Prius did not have plug-in recharging capability five years ago.
- Being a plug-in, the Volt has an extra AC to DC module for charging.
- The Volt battery is Li-ion and the Prius had a Ni-MH one.
- For hybrid thermal management the plug-in Volt uses liquid cooling while the Prius featured air cooling.
- In supplying the electronic components, the Volt seems to have a more diverse supplier base spread out over many more companies and their technology expertise. The Prius used mainly Toyota technology.
- High-voltage safety features of wiring and disconnects are comparable in both vehicles.
For further reading:
Innovation revelation: Engineering the Chevy Volt, Automotive Designline
This story was originally published in EDN.
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Dr DSP
5/11/2012 2:42 PM EDT
Seems like the need to only use the 'middle, of the battery is a real issue. You carry around 375lbs and only 'need' 1/2 of it? Like an extra passenger in the car all the time. What can be done to improve battery characteristics?
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Rick DeMeis
5/15/2012 12:26 AM EDT
Perhaps after experience is gained, a software update could allow wider use of battery capacity for longer EV range and better hybrid performance.
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blundar
5/23/2012 11:07 AM EDT
There is no mystery here - the charge/discharge/lifespan characteristics of LiIon batteries are pretty well known at this point. GM is doing this to try to preserve the life of the battery over time rather than go for range. The testers were unable to do so during their brief testing but I would be almost certain that the algorithm for battery usage would shift as the battery ages in order to shield the consumer from being aware of battery capacity decrease.
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