drive system

AC Propulsion's Reductive™ Charger
Reducing Costs and Increasing Range
Integrated Charging for the Electric Vehicle
Media reports and market surveys repeatedly cite these three complaints among reasons people will not buy electric vehicles (EVs).

  • Cost - Too expensive!
  • Range - Not enough range!
  • Infrastructure - Nowhere to charge!

The first complaint is true, but it doesn't have to be. By using clever designs, proven technology, and currently-available batteries, EV costs can be cut by thousands or even tens of thousands of dollars.

The second complaint is understandable, but not necessarily true. EVs do not have the range of gasoline vehicles, and never will. It does beg the question though, how much range is enough? The third complaint is preposterous. Electricity is everywhere. What's needed is EVs that can use the existing infrastructure.

That's why AC Propulsion invented the Reductive charger.

The Reductive charger allows the easiest EV access to existing electric power infrastructure, and does so in a way that maximizes convenience for the EV user. With a Reductive charger, the EV user can plug into any existing outlet from a 110V/15A household socket to an existing EV conductive wall box, or even a 240V/80A commercial welding plug. At its maximum 18 kilowatt (kW) power rating, the Reductive charger can provide a full recharge to an AC Propulsion eBox in just two hours.

The Reductive charger effectively solves the infrastructure problem by opening the existing electric power network to the EV user. By solving the infrastructure problem, the Reductive charger, perhaps surprisingly, also reduces the range problem. EV users know that range and charging availability are two sides of the same coin. The easier they can charge, the less concern they have about range, and the more they can use their EV like a conventional car.

Driving an EV equipped with a Reductive charger means you can charge your vehicle several times during the course of a day, without ever returning home. Without the Reductive charger, once the battery starts to run low, returning home to charge or driving to a dedicated charge station (which you might find is already being used, or worse, is not working at all) becomes a necessity. With the Reductive charger even an EV with limited range becomes much more useful because the miles per day can be high, even if the miles per charge is low.

By reducing the range problem, the Reductive charger, again perhaps surprisingly, reduces the cost problem. With the Reductive charger, which allows fast and frequent charging, the range provided by smaller or lower-cost batteries is more likely to be acceptable.

Furthermore, the Reductive charger itself saves cost. It is integrated with the vehicle drive system, so parts, size, and weight are all reduced. Over and above the battery-cost savings, the Reductive charger can take thousands of dollars out of electric vehicle cost.

Reductive charging can reduce maintenance and warranty costs

Because the reductive charger is based on an inverter, rather than a rectifier as in most other charging systems, it is inherently capable of discharging a battery pack by feeding the energy back to the utility. This capability allows a Reductive-equipped EV to perform battery pack capacity tests overnight at the customer's location, without the need to bring the vehicle in to a service location. This can dramatically reduce warranty costs, and vehicle downtime, since all battery capacities will be known prior to bringing the vehicle in for service.


Here are some FAQ's about the Reductive Charger:

What exactly is a Reductive charger?

The Reductive charger is a patented technology developed by AC Propulsion Inc. that takes the drive system and the battery charger for an electric vehicle, and combines them into a single unit. An EV drive system requires a powerful motor and expensive transistors called IGBTs to convert battery current into power that drives the wheels. An EV charger also requires similar transistors, and heavy magnetics to convert alternating current (AC) from the power outlet to direct current (DC) for the battery.

The Reductive charger uses the motor and IGBTs from the drive system to serve as the power elements of the charger. When the EV is being driven, the drive system works normally. When the EV is being charged, the drive system is re-configured as a charger. In this way only one set of large, heavy, and expensive components is needed.

Since the Reductive charger is based on a powerful drive system, it can charge at higher power levels than standard chargers. The Reductive charger in the AC Propulsion's AC-150 EV Power System can charge at up to 18 kW compared to 4-7 kW for conventional chargers. An inherent feature of reductive charging is nearly silent operation when running at less than 10 kW, since the cooling blowers need only to run at a very low speed.

The cost savings of Reductive charging are remarkable. Only $300 worth of additional components are needed to make the drive system into a 18-kW charger. Conventional EV hargers cost $2000 or more, and high-power EV chargers cost $10,000 and up.

Is it conductive or inductive?

The Reductive Charger is conductive. It can use conventional plug and socket sets or dedicated EV-style conductive connectors.

Is it onboard or offboard?

The Reductive charger is onboard the vehicle, integrated into the drive system. It is not a separate unit so it requires little space and weighs less than 10 pounds. The Reductive charger is designed to work with both 50 and 60 Hz inputs, from 100V to 240V. With special modification, it can accept DC charge power from off-board conductive chargers too.

If integrated charging is such a good idea, why doesn't everyone use it?

Electric vehicle manufacturers supporting conductive charging are all moving towards integrating the charging and propulsion electronics. However, while integrating a charger into an EV drive system is straightforward in concept, it is difficult in execution. There are many non-obvious design details that need to be done properly for this type of system to work at all. To meet all user needs, an integrated charger requires compatibility with the electric power infrastructure, safety, and high efficiency.

The Reductive charger limits ground currents to less than 5 mA so it does not trip ground-fault-interrupt circuits (GFI). At the same time, the Reductive charger limits conducted noise in compliance with FCC standards in order to avoid disruption of electronic appliances when the charger is plugged in. It operates at unity power factor for maximum power capability and low line distortion.

The Reductive charger achieves a high level of user safety because the drive system is double-insulated from the vehicle chassis.

Finally, the Reductive charger operates efficiently throughout its power range. Whether operating at its full 18 kW capability, or at end-of-charge conditions, when charging power is 1 kW or less, the Reductive charger makes efficient and economic use of electricity.

The Reductive charger meets these difficult user requirements with patented and proprietary designs resulting from a six-year research and development program conducted at AC Propulsion. Since 1992, the compatibility, safety, and efficiency have been proven in hundreds of thousands of miles of daily real-world use. AC Propulsion's broad patent covers most topologies of integrated charging, and equally importantly, most of the details required to make it really work. Reductive charging is standard in AC Propulsion drivetrain products. It is also available for licensing, giving the licensee a multi-year jump start in implementing integrated charging.

Does Reductive charging work with advanced batteries?

Reductive charging can work with any kind of battery. Charging profiles are controlled by a battery pack management system through a simple interface. The Reductive charger accommodates adjustable limits for AC line current, battery current, and battery pack voltage.

Why do you call it reductive?

Because the Reductive charger reduces reasons not to buy an EV.

  • Vehicle cost is reduced - the charger has fewer parts and is smaller and lighter.
  • Charge time is reduced - the charger is more powerful.
  • Infrastructure costs are reduced - the charger is compatible with any outlet.
  • Battery cost is reduced - easy charging eliminates the need for expensive batteries.