Introduction
	Conductive Connectors Well Established
	Factors and Features of Charging Systems
	Some Perspectives
	Final Comments

 

 

Introduction ~

The electric utility grid is ubiquitous. In the US and Europe it reaches almost everywhere people live, work, and congregate - and it is growing steadily. It provides the most convenient and useful power for stationary devices, and also is a great energy source for cars if the cars can tap into it easily at many locations. Tapping in means conveying electricity from the grid into the car via some connector, as part of a charging system that, either on-board or off-board, converts the AC from the grid to the appropriate DC voltage that charges the battery.

I have taken a broad look at the connector system options, both the successful inductive and conductive methodologies, and concluded that, considering all tradeoffs, there are compelling logic and evidence showing conductive connectors to be clearly the preferred technology – the technology that will most benefit the public.

The conductive connector subject for EVs is still in a state of flux and will be for some time. In order to meet near-term production deadlines, different vehicle manufacturers had to commit to specific solutions before a single standard was visible on the horizon. Configuration changes for chargers and vehicles are costly, especially once there is significant installed infrastructure, and so each company would prefer its connector configuration become the industry-wide standard. There will therefore be some discomfort as all this sorts out – and perhaps an interim business opportunity for whoever can provide a plug adapter that converts a non-standard plug into functioning as the emerging standard.

The success of the EV field depends on the wide availability of charging that can accommodate all vehicles. A manufacturer's discomfort in switching to the industry standard connector will certainly be less than that arising from trying to create its own exclusive charging infrastructure instead of using the industry's.

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Conductive Connectors Well Established ~

Conductive connectors for EVs are based on well-established technology. This technology has been the dominant low-cost global solution for accessing grid electricity ever since grid electricity became available.

• The standard 120 volt plugs and sockets of your home connect to your lamps, TV, heaters, battery chargers for drills, etc.
  
  
• Your washer and dryer at home may be on a 240 volt circuit (up to 40 Amps) but still use the conventional plug. (It can handle Level 2 EV charging, at say 9 kilowatts.) 3-Phase plugs have different standard pin shapes and locations, but operate just like their single phase cousins.
  
  
• For small vehicles, such as golf carts, the Bombardier EVs displayed at this event, and various indoor transporter carts, charging is through conductive connectors.
  
  
• For heavy off-road vehicles, such as fork lifts and airport ground service equipment, the charging connectors are conductive (handling high currents, often over 500 amps, but low voltages).
  
  
• Conductive connectors are also used for some mobile connections, such as trolleys and 3rd rail subways. Historically, slip rings have also served as power conductors.
  
  
• Most EVs , cars and buses, use conductive charging. The OEMs committed to this method include (alphabetically): BMW, Daimler Chrysler, Ford, Honda, Mazda, Peugeot, Renault, Solectria, and VW.
  
  
• The plugs presently in use for these vehicles are safe for the user and vehicle as evidenced by exhaustive testing, meeting SAE standards, and featuring UL approval. I can even envision safe conductive connector systems that can be operated by a driver without leaving the vehicle.
  
  

For slow, medium, and high charge rates of EVs (Level 1, under 1.5 kw; Level 2, under 14.4 kw; Level 3, under 240 kw) it has been demonstrated that one conductive connector standard can suffice. For extremely high currents, as with fork lifts, a higher current plug is needed (and is becoming available), but the basic electronics and redundant safety techniques are the same as for cars and buses.

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Factors and Features of Charging Systems ~

Safety
Any connector system must be safe. Both inductive and conductive connector systems are. This refers not just to the plug, but to the total system with its communication logic.

Open Architecture
To avoid unnecessary barriers inhibiting wide use, the interface (the connector) between grid and car must be standardized and available to all. This requires "open architecture" - any group can supply and use the apparatus. The charging devices need to fit the pertinent SAE documents (specs, or recommended practices) such as J-1772, J-1850, and J-2293 that relate to the mechanical connection and the redundant safeguards and communication logic between charger and battery management system. At present, the only open architecture is conductive, but there is still need within the conductive adopters to converge upon an implementation of these standards.

Fast Charging
Another important aspect of the connector standard is that it should easily support fast charge. Fast charge becomes convenient and a very cost effective "opportunity charging" (for buses and truck fleets that return routinely to a designated spot or service area). It is virtually equivalent to battery pack replacement, but much less cumbersome and labor intensive, and does not require multiple packs. At the high power rates of fast charge (well up into Level 3 charging) the simplicity and economy of conductive connector system compared to other methodology is very attractive. Multiple fast charges in one day puts priority on the battery management system that monitors the conditions of battery elements and controls the battery pack thermal management system and charging rates. Incidentally, growing evidence suggests that for lead acid batteries fast charge does not decrease battery cycle life. AeroVironment is not pushing conductive connectors because we created PosiCharge; rather, we created the PosiCharge conductive system because it looked like the most cost-effective approach to safe, convenient, easy-to-use charging at a 60 kw rate.

It is also worth noting that as battery packs for cars and light trucks grow in energy storage capability, faster charging becomes more needed. If the pack stores twice as much energy so as to power a heavier vehicle or achieve larger range, storage time doubles if the charge rate stays the same.

Total Systems Economy
As overall charging convenience improves, fast or slow, lesser energy storage may prove acceptable in some market niches – meaning cheaper or smaller battery packs

Versatility
Beyond the connector, there are many options for the associated software/logic of charging systems. Systems can be made compatible - such as Level 2 charging with a Level 3 charger. The same standard connector, with its versatile logic paths, can also handle wide system diversity such as on-board vs off-board charging, and various inputs from the battery management system.

In the long run, on-board charging with dual use of some of the vehicle's existing power electronics system seems especially attractive. However, if many vehicles are to feed regularly from the same electric "spigot", an off-board charging device may be the best compromise.

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Some Perspectives ~

In the pioneering stages of an important field one can expect pressures for different standards, for both sound technological and business reasons. From this starting point, as the field matures the evolution to a single standard that most benefits society is difficult. Vested interests, with embedded investments and inertias, have to deal with awkward compromises or conflicts. The situation is especially troublesome if proprietary standards prevent open architecture. The EV industry would certainly benefit from a quick, amicable resolution of the conductor standardization challenge so as to be free to focus on the more substantive challenges inherent in the EV field.

Unfortunately, there are many factors involved in standardization besides technical merit, economy, and putting customers at top priority. Society can lose, even though there are no villains.

The QWERTY keyboard story is a famous example of the cost to society from early adoption of a standard tailored to solving an initial problem, a standard that later was found to be inappropriate and troublesome as new technology solved the problem a better way. The early momentum quickly became too large to permit movement to a better solution, consequently this document is being typed by me on a computer using a QWERTY keyboard that was designed 120 years ago to slow down typing so as to keep mechanical typewriter keys from becoming entangled. Everyone knows of some more recent examples of problems associated with wide adoption of premature standards in information technology, a field moving so fast that it still has many pioneering aspects.

Getting people into EVs and therefore out of fossil fueled cars is a serious subject - not just a business opportunity. It directly decreases local urban pollution (NOx, volatile HC, CO, and particulates). There are other benefits from consuming less fossil fuel (less fuel is burned because much of the electricity on the grid comes from other sources such as hydro, nuclear, and wind, and because many modern EVs tend to require less energy per mile, because of the priority on vehicle efficiency aimed at ameliorating battery range limitations). The US balance of payment problem is helped by decreasing imports. The country gets less tangled up in the volatile politics and military adventures of the Mideast. And, less carbon dioxide gas is released, a gas that may be hastening significant global climate change.

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Final Comments ~

• The more there is standardization of charging connector systems, the more everyone wins. Neither suppliers, nor society, nor the individual user benefit from the splintering effect of multiple standards, changing standards, and incompatible hookups. (There are already some 3000 conductive charging stations for EVs in the U.S.)
  
  
• Standardization - with open architecture - facilitates increased purchases and uses of EVs. This helps manufacturers to make use of the economies of mass production. The lower prices attract more purchasers/users. Production increases and prices go down further. And so on with great positive feedback.
  
  
• Conductive connector systems for EV charging, built on a vast background of conductive connectors to operate fork lifts as well as our home appliances, feature the simplicity, economy, and thus a road to standardization that helps to spread the practical application of EVs.
  
  
• The standards now emerging handle a wide variety of charge rates and charger system details, and are likely to serve without fundamental change long into the future.
  
  
• Summary: There are important, difficult-to-solve challenges to achieving wide, consumer-driven purchases and utilization of EVs. The challenge of connecting the utility grid's electricity to the car's battery with suitable voltage and suitable safeguards, fitting one standard so that any EV can feed on the electricity at any charging site, is a tractable challenge. Considering economy, efficiency, simplicity, open architecture availability, and my expectation that a single, versatile standard can be created for the conductive connector for charging (and that one standard can be suitable for a long time), I find conductive connectors to be the preferred way to go.
  

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