Categories
Automotive Electric Vehicles

EV Charging Ports – Update

Figure 3: J1772 EV Charge Port Connector

Back in January I posted the blog, which discussed the two competing standards for EV charging ports. This is the “Beta vs VHS” debate in the EV world that will determine compatibility between vehicles and charging stations. In just the short time since I originally wrote that blog, there has been a fair amount of activity.

There are two basic levels available today for charging EVs today. The first is the SAE J1772 standard which provides for “Level 1” or “Level 2” charging. This essentially refers to 120V AC household current (Level 1) and 240V AC (Level 2, household or otherwise), which provides at-home, overnight charging or “opportunity” charging at public stations. The second is DC fast charging, which allows vehicles to be fully recharged in less than an hour, and where this debate centers.

The two competing styles are the CHAdeMO and SAE J1772 “Combo:”

EV Charging Ports 3
Figure 1: Nissan LEAF CHAdeMO DC Fast Charge Port (left) and J1772 Level 2 AC (right)
EV Charging Ports 2
Figure 2: J1772 “Combo” Connector (both Level 2 AC and DC Fast Charging)

The competing standards are being pushed by both auto manufacturers as well as companies that are rolling out the public charging infrastructure (charging stations). Japanese automakers Nissan, Toyota, and Mitsubishi have been using the CHAdeMO standard for several years now, on a variety of cars. In North America, only the Nissan LEAF and Mitsubishi i-MiEV are equipped with this port currently. Even with only two vehicles sold with this port today, it still has the lions share of the current market- since the SAE “Combo” standard is still not being sold anywhere. With respect to available charging stations, more than 150 CHAdeMO stations are in use today, provided by Blink, Aerovironment, EATON, and other existing suppliers of stations and charging equipment. This is by far the dominant standard.

The SAE “Combo” standard is an up-and-comer, though. While not currently sold on any vehicles or available at any charging stations today, manufacturers such as GM, Ford, BMW, and Volkswagen have announced that they will be supporting this standard in 2014 and later models. Additionally, Car Charging Group, one of the largest charging networks suppliers in North America, has announced that are endorsing the standard. While this is just one of many suppliers, it is one, and it is first. More are likely to follow.

To further muddy the issue, perhaps the most visible EV company, Tesla, has decided not to support either standard (not directly, at least). Their “Supercharger” stations, which provide for DC fast charging, use a proprietary setup. They have, however, announced that they will be providing an adapter to allow their vehicles to use the SAE “Combo” standard. Consider this at least a tip-of-the-hat towards the SAE standard.

This is far from over and I am sure will continue to evolve rapidly. If new vehicles like the 2014 Chevy Spark EV, which uses the SAE “Combo” standard, take off, it could be a game changer. Much like the Betamax vs VHS debate, it will only take one or a handful of early adopters to cause one standard to take off and the other to languish.

Categories
Automotive Electric Vehicles

EV Charging Ports

Those unfamiliar with the design or use of EVs may be interested to discover there is a heated debate going on about EV charging. As everyone is probably well aware, EVs’ Achilles heel is their range, which is a direct function of their battery capacity and thus their ability to charge quickly.

There are two basic schemes available today for charging EVs today. The most popular one (based on vehicles sold) is the SAE J1772 standard “charging station” that operates off of single-phase AC household current. The charging station manages the link from household

EV Charging Ports 1
Figure 1: J1772 Charge Plug and Port

power to the vehicle much like an automated disconnect or GFCI does. The vehicle then has an intelligent, on-board AC/DC converter that rectifies the provided household current and steps up (or down) the AC voltage to a voltage that allows for charging the on-board DC battery pack. The original standard was written to provide for 80-A charging at 240V, although most implementations are 30A or less. “Level 1” indicates 120VAC charging (usually less than 16A), “Level 2” indicates 240VAC charging (less than 32A). Actual current usage is defined by the AC/DC in the vehicle. Most EVs and plug-in hybrid sold today are provided with some form of portable J1772 (Level 1) charging station that the operator can plug into the wall. Open-source DIY kits have even sprung up for these chargers due to their popularity and simplicity (essentially a contactor w/processor to communicate with the vehicle to negotiate the connection).

The second (and much less popular) scheme is DC fast charging. In this case the charging station not only provides a connection to the vehicle but also rectifies and steps up the AC to DC and provides a DC source that can be directly connected to the vehicle.

EV Charging Ports 2
Figure 2: J1772 “Combo” Connector (both Level 2 AC and DC Fast Charging)

Direct DC charging has one primary advantage: the speed of charging. Every EV is designed to charge at slightly different rates, but when you consider the battery pack size (16kWh for the Volt, 24kWh for the LEAF, 85kWh for the upgraded Tesla Model S), it becomes readily apparent that with a maximum of 200A, 220V service at home, it takes a while to charge. If you need a charge in a hurry (especially crucial when on the road), high current and voltage is needed.

EV Charging Ports 3
Figure 3: Nissan LEAF J1772 Level 2 and CHAdeMO DC Fast Charge Ports

The primary detractor for DC fast charging is the requirement for a large and expensive power supply to provide the AC/DC conversion. This is not a DIY home project! Voltages greater than 400V and currents greater than 100A may be supplied to fast charge the vehicle (a depleted 24kWh LEAF battery can be recharged from nearly dead back to full in less than 30 minutes). These are not small systems and require a hefty electrical service from the local utility company to operate.

There is also a raging debate over the specification and connectors for DC fast charging, which has not been standardized yet. As of today, the two competing styles are the CHAdeMO and SAE J1772 “Combo.” CHAdeMO is a consortium of Japanese automakers that have specified a DC fast charge scheme and connector which has already been deployed on multiple vehicles (Nissan LEAF, Mitsubishi iMiEV, and others). The odd name is an abbreviation of “CHArge de MOve”, equivalent to “charge for moving,” also a pun for O cha demo ikaga desuka in Japanese, translating to “How about some tea?”.  This connector has the advantage of being the first put into production, as well as the flexibility of being deployed in conjunction with, or instead of, a Level 1 or 2 J1772 charge port.

The SAE J1772 “Combo” is, as the name implies, an extension of the original J1772 specification that combines DC fast charge contacts with the Level 1/Level 2 contacts in one connector and port. This simplifies the design, but the design is already at a disadvantage being second to show up to the party.

For certain this debate will rage on for at least a short while. Only time will tell which standard emerges as dominant.

Categories
Electrical

What Makes a Good Connector (or a Bad One?)

My father and I both joke about how putting up the Christmas tree (specifically, stringing lights) has to be the number one cause for divorce in the US. Each year it is about the most painful 4 hours of my life that I spend. It only takes about 2 to string all the lights on our 9 foot tree, but I inevitably dedicate another 2 hours to replacing burned-out bulbs and identifying dangerous strands or sockets (side note: the wife and I can’t stand the flicker associated with LED bulbs).

Which leads me to the reason for writing this: The Christmas tree light socket. It has to be

The Worst Connecter Ever

Figure 1 The Worst Connector Ever

the worst connector on earth. First, they are nearly impossible to remove. The bulb base fits almost flush into socket. No lip or feature to pull on; enter broken and bloodied fingernails. The retention has to be in the hundreds of pounds. I often find I need surgical tools to remove them. Second, they provide for ridiculously poor and unreliable contact. About a quarter of the bulbs that are out just make poor contact and removal/reinsertion fixes the issue. Third,

they are all just different enough that they aren’t interchangeable. I have a collection of Ziploc bags with different types. I inevitably have to swap bulbs between base types. That’s a plus- at least the bases are easy to swap.Watch movie online The Transporter Refueled (2015)

 

This got me to thinking… what makes a good connector? This may sound obvious, but do connector designers out there have a “bible” or best practices they go buy? I would recommend this:

  1. Electrical performance. This goes without saying. Most connectors do this well, matching the electrical properties for the application.
  2. Ease of assembly. Make the connector easy to assemble (by hand or automated) with minimal special tooling.
  3. Ease of disassembly. See #1 above. Usually neglected because, well, most connectors don’t have to be disassembled.
  4. Ease of connection/separation. Use simple locking features that make connections quick and easy.
  5. Reliability. Both electrical and mechanical… make sure it holds up to the environment.
  6. Compatibility. I realize there is a marketing component to this, but the more “open” and compatible a connector standard is… the better.

We’ve all had dealings with one in the past. Maybe it was at a previous job. Or a previous project. We’ve all used a connector at one point or another that made us think… “What the hell was that engineer thinking?!” What are some of your “worst connector ever” experiences, and what additional best practices do you think there should be?

Also, in case you are wondering, yes, I plan to be first in line on December 26th to finally buy a pre-lit tree. I’ll have an excuse to throw everything away and start over when a bulb or socket goes out.

Categories
Automotive Electric Vehicles

Noise in Electric and Hybrid Electric Vehicles

Noise in vehicles (of all types) is fairly well understood. Heavy inductive loads (and corresponding inductive noise) can be found, such as in a variety of motors used for everything from accessories, such as window motors, to high-speed motors or pumps used in antilock braking or electric power steering systems. Ignition systems in internal combustion vehicles are notorious for broadcasting the brief but powerful discharge of the ignition coil. Alternators by nature “alternate” and require filtering to make sure their AC is properly converted to DC and not delivering an AC waveform downstream. A lot has been done over the years to mitigate these issues in vehicles. Critical signals are shielded, inductive loads are properly suppressed with blocking diodes, and alternators are almost universally filtered now to make “alternator whine” filter kits a distant memory (ask a modern teenage car-audio aficionado if he knows what that is).

Enter the electric car.

A few things have happened with the introduction of the electric car. First… the electric motor. That in itself is not very revolutionary or even an issue in itself. This, though, combined with the lack of historical knowledge, is. Developers of EVs tend to be young by nature- new, innovative technology on new programs. New startup companies. New ideas. Unfortunately, all this “new” may push out some of the “old.” In addition to this, you have the introduction of vehicles engineered in China, originally powered by internal combustion, transplanted to the US for a conversion to electric (the Wheego and Coda come to mind).

EVs are subject to many of the same noise sources that other (internal combustion) vehicles are. Where items specific to internal combustion (ignition noise, alternator whine) are omitted, they are replaced by noise from the electric motor and motor controls. This technology has transitioned overwhelmingly to synchronous AC motors. DC motors have the same noise issues but to a much lesser extent, and they tend to be focused on a single PWM frequency in the tens of kilohertz. AC controls can vary much more widely and with load.

EV drive motor noise is relatively easy to combat; like many other noise sources, cable routing is key. We all know that every wire is an antenna… so keep your antenna routed away from the transmitter you don’t want to receive from! Routing unrelated circuits away from drive motor cables and power supply cables near the motor controller electronics is key. Sensitive or low-voltage/high-impedance circuits will need to be shielded. Software averaging of sensor signals, where possible, is also of great benefit.

My other, more abstract points about the loss of knowledge and importation of vehicles/chassis is based on the trend towards startups and building teams from scratch. Larger, well-funded companies like Tesla had the ability to hire seasoned veterans who brought a lot of knowledge with them. They also had a long development or incubation period to develop a lot of knowledge. On the other hand, many other smaller startups or some freshly minted teams at larger companies are starting with a deficit of the basic knowledge of vehicle systems and handling noise in vehicles. Similarly, vehicles are being brought over that were designed for internal combustion but fitted with an EV powertrain stateside. Included accessory wiring may not provide for necessary noise immunity when an EV powertrain is laid in where available space allows. This may also not show up until multiple vehicles are built and minor variances in those vehicles place cables just within reach for inductively coupled noise. These are all items that have to be considered for anyone working on one of these teams.

While the modern car audio nut may not have to be bothered with filters for the alternator whine like their fathers, they will still have to listen to stories about them (just as we had to listen to stories about multivibrators).