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Bench Talk for Design Engineers

Bench Talk

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Bench Talk for Design Engineers | The Official Blog of Mouser Electronics


Power Management the Hux Way Caroline Storm Westenhover

Since processors are following Moore’s Law and batteries are not, people have to look at the other side of the equation, the load, to increase battery runtime. It can be the user’s choice, like ultra low power modes available on new smartphones. Or it can be an old process that is optimized, like migrating from Bluetooth to BLE. Optimizing old processes is possible because of power management options made available by powerful and efficient processors. Processors can be put into low power modes without sacrificing response time and can be run on a fraction of the energy required of already efficient systems. For example, LEDs are already low power, but their power consumption can be further lowered by dimming it with a PWM signal. This is practical because power demands of processors are a fraction of the LEDs.

 

Today I would like to highlight a bit more complicated power management routines being applied to plug-in hybrid electric vehicles (PHEVs). For the most part, in commercially available vehicles, batteries and ultracapacitors are managed in real time. Accelerating? Draw power from the ultracapacitors. Braking? Charge the batteries. Cruising along: charge the ultracapacitors from the batteries. Starting in 2008 there has been research that uses GPS, traffic and geographical information systems (GISs) to optimize the power management system.

 

PHEVs maximize the amount of money saved when they end a trip with the battery pack completely discharged, usually somewhere around 30% state of charge (SOC). For some time after PHEVs came out the way this was achieved was to almost solely use the battery until it reached 30% SOC. Then switch to gas and began regenerative charging of the batteries. There was no optimization. Batteries are more efficient when discharged at a more constant rate, whereas gasoline consumption can handle stop and go action with a proportionally smaller drop in efficiency. Furthermore, before a driver hits city lights or stop-and-go traffic, the batteries should be at a low enough SOC to be charged by the brakes. To implement these ideas researchers at the University of Wisconsin employed traffic data to figure out what was the optimal use of the battery, using the battery when it would most reduce the fuel consumption, and arriving at the destination fully discharged. Using this method they found that they could get a 52.8% improvement in fuel consumption. To be clear, this was for SUVs and only researched fuel consumption, not total cost. This research was done in 2008 and has been cited by 213 other papers, thereby continuing the forward progress. Traveling from point A to point B will always require a certain amount of force. But a long time ago, in a galaxy far away, The First Order got something like 99.99999999% efficiency on the Starkiller Base. I mean, they had to, otherwise the charging weapon would have cooked everyone inside. Therefore, based on Sci-Fi’s long history of accurate representations of technological capability, people of the future should be able to get 99% efficient travel. At least.

 



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My name is Caroline Storm Westenhover. I am a Senior Electrical Engineering student at the University of Texas at Arlington. I am the third of seven children. I enjoy collecting ideas and theories and most enjoy when they come together to present a bigger picture as a whole. Perhaps that is why I like physics and engineering.  My biggest dream is to become an astronaut.


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