Electronic Design

Bob's Mailbox

Dear Bob:

Re: Your Electric Car Stuff column in the August 8 Issue.

From 1978 to 1986, I was involved in the "Electric Adventure," the U.S. Dept. of Energy's program to put Electric vehicles on the road and develop test data and experience in a real-world driving environment. For eight years, under contracts with the U.S. Dept. of Energy, my joint-venture partner (a new car dealer in Dallas) and I leased Electric cars to individuals and businesses in the Dallas, Texas area.

All of these cars were internal combustion engine (ICE) cars before conversion to Electric vehicles (EVs). They were, therefore, not the most optimum platforms to evaluate the limits of EV technology. They tended to be heavier than they needed to be because of all-steel construction, and extra bracing was needed to keep the U.S. Dept. of Transportation happy.

In all, we had about 20 cars on the road, including Ford Escorts, Ford full-size sedans, Pontiac compact sedans, Dodge Omnis, and even a Mercedes Benz 190. The performance of these cars was certainly adequate for any type of driving mission within the obvious limits imposed by battery capacity. Some typical characteristics of these cars is listed below:

¯   Top Speed----At least 70 mph (the MB 190 would do 80 mph).

¯   Range on Full Charge----45 to 55 miles (in the city or at highway speeds).

¯   Batteries Used----Lead-acid, 6-V, golf-cart batteries in a series string.

¯   Acceleration----Brisk up to 20 mph, about 0.1 G after that.

¯   Efficiency----0.3 kWh/mile dc, and 0.5-1 kWh/mile ac (from the power line).

¯   Battery Life----More than 10,000 miles until the range fell to 65%.

¯   Battery Replacement Cost----About the same as now, approximately $1000.

Safety Features:

¯   Every car had a manual electronic disconnect "knife switch" attached to a cable and handle under the dash, similar to the hood release, but red. All were fitted with fuses as well. A traffic accident did occur, but you should have seen the other guy! The extra steel and mass of the EV kept it intact and drivable, not so with the ICE it hit.

¯   The batteries were housed in steel boxes with lids snapped down tight, both under the hood and in or under the trunk. Forced-air ventilation kept hydrogen at a low level. A sensor warned of ventilation failure.

¯   Ground-fault circuit interrupters were in each car to disconnect the 240 V ac if as much as 1 mA of ground-fault current occurred. The high-voltage battery (120 V) was not connected to the chassis of the vehicle. The 12-V system was, as usual, connected with the negative to chassis.

Accessories:

¯   Several cars had air conditioners that used about 1 kW to run when on. Since the vehicle motor used about 10 kW, the range was only reduced 10% or less----a small price to pay for comfort.

¯   All cars had heaters and defrosters. Some were gasoline-powered, some electric. Again, about 1 kW was required.

¯   All cars had power brakes, powered by a small electric motor vacuum pump.

¯   All had radios.

¯   Some had power steering, automatic transmissions (not really needed), electric windows, seat heaters (the greatest), etc.

In other words, anything you can hang onto an ICE you can hang onto an EV. The EV's motor consumes so much of the available energy, the other stuff doesn't matter much.

Some observations:

At first it seems different driving an EV. Then you realize one day that you've been driving around town in an EV without giving it a second thought! I think that sums up the ease with which one adapts to EVs.

In my final report in 1985, I recommended a small ICE auxiliary power unit (APU) be installed in EVs to provide increased range and reliability. "Don't leave home without it." Eventually, fuel cells would replace the ICE APU, but the high-discharge-rate battery would still be needed for acceleration.

Batteries that have twice the energy of lead-acid have existed for at least 10 years, and they did consistently give 100-mile-plus ranges in these same cars. On a life-cycle cost basis, they are less expensive than lead-acid and would last over 100,000 miles. Edison invented them for electric cars 75 years ago----the nickel-iron battery. Some have been in use that long!

What about GM's Impact EV? They achieved a 125-mile range using lead-acid batteries. How did they do it? With a very lightweight chassis, low-rolling-friction tires (very high pressure), and a clean aerodynamic shape. Now, if you put in an Edison battery and an APU....

GEORGE H. THIESS

IZU Products

Lufkin, Texas

Your experiences with electric cars are quite encouraging. There's no doubt the CARS are adequate, it's just the BATTERIES that don't have enough range or life. Maybe nickel-iron will prevail. Flywheels may need more study, but I think they are "closing fast on the outside."

Still I don't favor 4000-lb. cars, whether ICE or EV. The real economy of EV will come at the 2000-lb. level. (If I took all the junk out of my Beetle, it might attain 2000 lbs.----RAP

Dear Bob:

First, I'd like to let you know that I have been enjoying your column in each and every issue of Electronic Design. In your September 5 column on Rendezvous Stuff, you asked about what could be done to circumvent the communication difficulty you encountered. The following is my input:

It's possible for the event coordinator to use a Telephone Answering Device (TAD) that has remote programmable OutGoing Message (OGM) capability. This feature is available on many of the newer answering-machine models, as well as most voice-mail systems. The coordinator should start with an OGM that encourages callers to leave a message if they need assistance, and to call back after a while for updated instructions.

During the initial phase of the gathering, the coordinator should check the InComing Messages (ICM) recorded on this TAD. When a "request for assistance" ICM is noted, the coordinator can change the OGM to include specific instructions in response to the need of the "lost party." When that party calls again, the OGM will be providing the updated information.

Better yet, once the coordinator has identified a communication device at the gathering site, such as the cellular phone number belonging to one of the parties already arrived, the OGM can be updated with such information. Then, all "late" or "lost" parties can easily reach the group at the gathering.

Hope the above thoughts can be of some help in the future. By the way, this technique can work for unplanned situations if the parties involved have some prior mutual understanding of this facility....

ABRAHAM Y. CHEN

AC International

Mountain View, Calif.

You're quite right. I neglected to say in my column that when a group is entering a strange place (carnival, big store, city, swamp, etc.) they should always agree in advance on a good time and place to rendezvous if separated.----RAP

All for now. / Comments invited!  RAP / Robert A. Pease / Engineer

Address:

Mail Stop D2597A

National Semiconductor

P.O. Box 58090

Santa Clara, CA 95052-8090

 

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