("The Ultimate EV Charger")
HFXC-5000
High Frequency Transformer
Onboard Battery Charger
for Electric Vehicles
The Ultimate EV Charger
Electric Vehicle News, April '97
by Bob Wing
Last month I drove west of Santa Rosa, California on Sebastopol Road looking for the Coherent Power shop. I had last been on this section of the road 50 years ago to rent a house for my first job at Pacific Bell after completing my Graduate Business School degree at Stanford. This part of the road looks no different now except there are fewer cars, no trucks, and the railroad no longer operates as the tracks are up for a bicycle trail. The freeway is one-half mile away, leaving the original farm houses much as they were when built.
Les Piper, business manager, met me and showed me around the shop. CEO Volker Scholze then came in to discuss the technical details. I had met Volker the previous year when he came to my EV Show in Point Reyes Station. And I met Ellen James, the CFO/chief designer. The Coherent HFXC-5000 charger is the result of a successful five year R & D plan leading to production.
The Coherent charger is 5 kW and it's just what I have been waiting for. It is mounted in a metal box 7" high x 12" x 17" and weighs 33 pounds, and is isolated from the AC line by a high frequency transformer. It has the best power factor correction I have seen on any charger, PF of 99.9+%, and 3-5% current THD (Total Harmonic Distortion) over the entire range of power from 500 to 5000 watts, well below the limits proposed by the IEEE 519 and the more stringent requirements of the Electric Vehicle Association of the Americas. Output voltage is for most usual nominal battery pack voltages between 120 VDC and 312 VDC, the highest at the present time. [Nominal voltages as high as 528 VDC are now being produced utilizing Coherent Power technology.]
The charger works on 95-145 VAC at 1800 watts and 195-265 VAC at 5000 watts. There is an optional version that operates for all of the above including 195-265 VAC 3-phase.
The charging cycle is automatically regulated, for wet or sealed batteries, for current control, temperature compensation, gassing and equalization. Output voltage thresholds, two upper and one lower, are adjustable. This means that my Optimas can have a top setting for daily use and every two weeks have an automatic three-hour equalization charge, all through my Rudman regulators. Output current is programmable for adjustment for each of up to nine sequential steps. [The latest version of the charger provides a separate voltage threshold adjustment for each of the nine steps of the algorithm.]
Thirty HFXC chargers are available for beta testing. Of these five have been delivered as of this writing. At $5,000 per unit, the charger is pricey for home conversions, but it should be a good candidate for vehicle integrators and manufacturers. Having seen the extreme care taken in design and fabrication and the clean power factor, I would not be surprised to see the HFXC capture a good share of that part of the market not limited by the "Not Invented Here" factor.
(Contact: Les Piper, 768 Brittain Lane, Santa Rosa, CA 95407; tel 707-523-0335, fax 707-546-4538, e-mail piper@coherentpower.com)
[Bob Wing is West Coast Correspondent for EV News and an EV consultant. He can be reached at POB 277, Inverness, CA 94937-0277; tel 415-669-7402, fax 415-669-7407, e-mail bobwing@nbn.com]
[Copyright © 1997 Bob Wing & Electric Vehicle News. All Rights Reserved.]
HFXC-5000 Product Reviews: