Mar 5, 2025 07:00 PM
We’re charging our cars wrong
https://spectrum.ieee.org/analog-ic-design
EXCERPTS: If there’s one thing we could do now to hasten the transition to electric vehicles, it’s this: Build a robust public EV-charging infrastructure. While the media has focused on vehicle performance and range, consumers have always been clear that they want electric cars to do essentially everything their old vehicles do—including long overnight trips.
To those who don’t yet own an EV, a robust infrastructure may seem unimportant. Studies, after all, show that in developed markets, as much as 90 percent of all charging takes place in the home. It turns out, however, that the remaining percentage of charging is critically important. Drivers of delivery trucks and taxis, residents of apartment buildings, students on their way to college, families on vacation, and countless others have learned that driving an EV can be a struggle where public charging is scarce or unreliable. A 2022 survey by Forbes, for example, indicated that 62 percent of EV owners were so anxious about EV range that they had at times curtailed their travel plans.
[...] When we’ve asked potential EV owners what’s limiting EV adoption, they often point to limited access to charging stations—especially to fast public charging. The operators who own these charging stations have said it as well, and they also cite the high cost of equipment—a DC fast-charging station with four ports can cost between US $470,000 and $725,000. If equipment costs were lower, they say, they would install more recharging stations. It could be a virtuous circle: The recharge businesses would do better, EV owners would benefit, and more people would consider buying an EV.
The question is, can EV charging be done more economically and efficiently? More specifically, is there a way to reduce recharge station complexity and bring down the high cost of fast-charge stations—and, in so doing, significantly boost EV penetration without sacrificing safety? The answer is yes, and here’s why.
[...] A key safety feature of existing EV chargers is an isolation link ... the charger must protect users from electric shock. ... This isolation link is very expensive. It accounts for roughly 60 percent of the cost of the power electronics in a typical EV, and it’s also responsible for about 50 percent of the charger’s power loss.
We estimate that the cost of the bill of materials and assembly of a galvanically isolated charging port is about $300 per kilowatt. So a single 300-kW port in a public charging station includes about $90,000 of power electronics, of which about $54,000 is for the isolation link.
Do the math: A charging station with four ports includes approximately $360,000 in power electronics, with more than $200,000 of that going for galvanic isolation. To get an idea of the total costs in a country, say the United States, multiply that 60 percent cost reduction of the power electronics per charger by the multiple ports at the more than 61,000 public EV-charging stations in the United States.
[...] These are among the main reasons why we propose to eliminate galvanic isolation. Billions of dollars of capital and energy expenses could be saved. Hardware reliability would improve...
[...] The requirements for eliminating the isolation link are not terribly complex or costly. Two issues in particular need to be addressed: the risk of electric shock and the compatibility between the utility and battery voltages.
[...] Eliminating the risk of electric shock isn’t the only issue that we must deal with if we are to get rid of galvanic isolation. There’s also the issue of voltage—specifically, the need to prevent mismatches between the utility’s AC line voltage and that of the EV battery.
[...] It’s time to simplify the EV recharging process and make it more cost effective. But that surely won’t happen without a discussion of galvanic isolation in the technical community. So let the discussion begin! We’re convinced that eliminating the isolation link should be the first step toward the robust charging infrastructure that the EV transition so desperately needs...(MORE - missing details)
https://spectrum.ieee.org/analog-ic-design
EXCERPTS: If there’s one thing we could do now to hasten the transition to electric vehicles, it’s this: Build a robust public EV-charging infrastructure. While the media has focused on vehicle performance and range, consumers have always been clear that they want electric cars to do essentially everything their old vehicles do—including long overnight trips.
To those who don’t yet own an EV, a robust infrastructure may seem unimportant. Studies, after all, show that in developed markets, as much as 90 percent of all charging takes place in the home. It turns out, however, that the remaining percentage of charging is critically important. Drivers of delivery trucks and taxis, residents of apartment buildings, students on their way to college, families on vacation, and countless others have learned that driving an EV can be a struggle where public charging is scarce or unreliable. A 2022 survey by Forbes, for example, indicated that 62 percent of EV owners were so anxious about EV range that they had at times curtailed their travel plans.
[...] When we’ve asked potential EV owners what’s limiting EV adoption, they often point to limited access to charging stations—especially to fast public charging. The operators who own these charging stations have said it as well, and they also cite the high cost of equipment—a DC fast-charging station with four ports can cost between US $470,000 and $725,000. If equipment costs were lower, they say, they would install more recharging stations. It could be a virtuous circle: The recharge businesses would do better, EV owners would benefit, and more people would consider buying an EV.
The question is, can EV charging be done more economically and efficiently? More specifically, is there a way to reduce recharge station complexity and bring down the high cost of fast-charge stations—and, in so doing, significantly boost EV penetration without sacrificing safety? The answer is yes, and here’s why.
[...] A key safety feature of existing EV chargers is an isolation link ... the charger must protect users from electric shock. ... This isolation link is very expensive. It accounts for roughly 60 percent of the cost of the power electronics in a typical EV, and it’s also responsible for about 50 percent of the charger’s power loss.
We estimate that the cost of the bill of materials and assembly of a galvanically isolated charging port is about $300 per kilowatt. So a single 300-kW port in a public charging station includes about $90,000 of power electronics, of which about $54,000 is for the isolation link.
Do the math: A charging station with four ports includes approximately $360,000 in power electronics, with more than $200,000 of that going for galvanic isolation. To get an idea of the total costs in a country, say the United States, multiply that 60 percent cost reduction of the power electronics per charger by the multiple ports at the more than 61,000 public EV-charging stations in the United States.
[...] These are among the main reasons why we propose to eliminate galvanic isolation. Billions of dollars of capital and energy expenses could be saved. Hardware reliability would improve...
[...] The requirements for eliminating the isolation link are not terribly complex or costly. Two issues in particular need to be addressed: the risk of electric shock and the compatibility between the utility and battery voltages.
[...] Eliminating the risk of electric shock isn’t the only issue that we must deal with if we are to get rid of galvanic isolation. There’s also the issue of voltage—specifically, the need to prevent mismatches between the utility’s AC line voltage and that of the EV battery.
[...] It’s time to simplify the EV recharging process and make it more cost effective. But that surely won’t happen without a discussion of galvanic isolation in the technical community. So let the discussion begin! We’re convinced that eliminating the isolation link should be the first step toward the robust charging infrastructure that the EV transition so desperately needs...(MORE - missing details)