413 ballast, Ohm's law, and other musings

From: "Christopher Middlebrook" <delamothe@xxxxxxxxxx>

Date: Tue, 2 Mar 2004 15:34:10 -0500 (EST)

Current = Voltage / Resistance Suppose you have a constant resistance (DC resistance of the coil plus any other resistances along the path) As you increase the voltage, the current increases also. This is why your 6V generator was rated at a higher current output than a 12V alternator. This is also why your 6V system does not need a ballast (or current limiting) resistor. Indeed the new ignition modules have built-in curent limit resistors. The way resistors are done in voltage regulators and ignition modules is with resistive inks. The entire circuit is silkscreened on an aluminum oxide substrate. The traces are conductive inks, and the resistors are mixes of resistive inks. Then after the substrates are cured, a laser trims the resistors to within .01% of the desired value. Believe it or not this process is a lot cheaper than buying the parts, and it increases the reliability of the circuit many times. Now a lot of this process is becoming "old school" as a lot of upcoming designs rely on ASIC's (application specific integrated circuits). That is, the entire design is etched on a silicon wafer to make a unique chip. The latest designs from Visteon (Ford) and Delphi (GM) incorporate ASIC designs in their voltage regulators and DIS (distributorless ignition system) modules. That makes for even more reliable parts with the downside that there is little that can be done for troubleshooting except scrapping the device. Now going back to the voltage - current topic; for the past 9 years, the auto industry has been doing research on a new voltage standard for all cars. Yes, the 12 volt system will be getting replaced by a 52 volt system. The rationalle is that cars today have a large electrical load on them with sensors, computers, etc. A 52 volt battery can deliver more power without having to increase the wire diameter (or decrease the gauge, however you want to see it). This will result in a savings to the industry in weight and cost due to smaller gauges of wires in harnesses. Essentially from the formula given at the beginning of this rant, an increase in voltage provides an increase in current. When will this new standarsd take place is another question. The battery manufacturers and the auto industry are still toying with the type of battery and such. One design involves a hybrid battery that would have a 5-8 volt portion isolated from the high load portion, dedicated to keeping the electornics in their "sleep mode" when the car is not running. Regardless, this will be the new de facto standard. I mentioned that an ignition module that draws more current in the pretense that more horsepower will be obtained is laughable. An 8 amp load on an alternator requires about 2HP to turn the rotor. So essentially any horsepower gainedgoes out in the wash when the motor is turning the alternator. Now grant, its not a constant 8A. Usually it's a 50% duty cycle or more depending on the type of ignition and dwell that's going on. Chris Middlebrook 62 Custom Southampton --- On Sun 02/29, Bill Watson < wwatson@xxxxxxxxx > wrote: From: Bill Watson [mailto: wwatson@xxxxxxxxx] To: mailing-list@xxxxxxxxxxxxxxxx Date: Sun, 29 Feb 2004 02:04:22 -0800 Subject: Re: IML: 63 413 ballast If voltage has nothing to do with it, why is the ballast resistor only on 12 volt systems, and not 6? The 12 volt charging systems, in the 1960's, put out 26 to 39 amps (depending on application). Yet the old 6 volt charging systems put out 35 to 45 amps (depending upon application). The current draw on a 1960's mopar engine, to the coil, was 1.9 to 3.0 amps, and the ballast resistor has a resistance of 0.5 to 0.6 ohms at 70-80 F. Sort of midway of the .1 to 1 oh, of the current limiting resistors on today's cars. And I would say a built-in current limiting resistor is just another way of saying ballast resisitor. It does the same thing, only using modern technology. But that still does not answer my question. Bill Vancouver, BC ----- Original Message ----- From: "Christopher Middlebrook" <delamothe@xxxxxxxxxx> To: <mailing-list@xxxxxxxxxxxxxxxx> Sent: Saturday, February 28, 2004 12:50 PM Subject: Re: IML: 63 413 ballast > > The ballast resistor has nothing to do with voltage. It is strictly for current limiting so that you don't overload the charging system and burn up the points, or power darlington transistor in the modern case. 5-8 Amps is the nominal current depending on what type of ignition system you have. Fancy ignition systems that tout performance put out a little more current, but in all actuality, unless you are running a very high compression ratio, 6 amps is ideal. Anything more than that just puts more load on your motor from the alternator as it reacts to the additional need. > Modern electronic ignition and distributorless ignition systems have built-in current limiting resistors (.1 - 1 ohm depending on the design). This is why you seldom see ballast resistors or resistive wires any more. > > An inductive ignition system (coil) is efficient for up to 4000 RPM's. Beyond that, there isn't enough time to create an adequate field in the coil, and consequently the current limit begins to drop as RP M's increase. That's where capacitive ignition takes over. > > Chris Middlebrook > 62 Custom Southampton > > > > > --- On Sat 02/28, Bill Watson < wwatson@xxxxxxxxx > wrote: > From: Bill Watson [mailto: wwatson@xxxxxxxxx] > To: mailing-list@xxxxxxxxxxxxxxxx > Date: Sat, 28 Feb 2004 09:37:35 -0800 > Subject: Re: IML: 63 413 ballast > > Actually, all North American manufacturers adopted a resistor of some sort when they switched to 12 volts. Some Studebakers had a resistor wire running from the ignition switch to the coil. When the key is in the "Start" position, power is sent to the coil directly from the ignition switch - a full 12 volts. Once the car is started and the key put in the "On" postion, power runs through the resistor, giving about 6 volts at idle.. Which is why when your ballast resistor goes, the engine dies when you turn the key to "On" from "Start". During the start procedure, the resistor should show 0 volts as no power is running through it as i8t is bypassed,. Bill Vancouver, BC ----- Original Message ----- From: IMP7T@xxxxxxx To: mailing-list@xxxxxxxxxxxxxxxx Sent: Friday, February 27, 2004 11:48 AM Subject: IML: 63 413 ballast I assume that Chrysler is the same set up as GM. I believe that all ig > nition coils are 6 volt. Your ballast resister knocks the 12 volt to six volts while the car is running. During cranking you have a wire that runs from the starter circuit that goes to the coil and gives the coil 12 volts during cranking only. This way you get full spark during cranking. I could be wrong, but donā?Tt think so. Anyone see a 6 volt car with a resister? Sooo! After all this, I would say if you are questioning the resister, bypass it for a test. Donā?Tt let it run to long.. If it starts and runs, you have a problem in t he resister. If it still does not run, something else is the problem. You could also test the resister with a volt meter. 12 volts one side, 6 volts the other. During crank 12 volts on both sides. 1970 Imperial and a couple of street rods ----------------- http://www.imperialclub.com ----------------- This message was sent to you by the Imperial Mailing List. Please reply to mailing-li > st@xxxxxxxxxxxxxxxx and your response will be shared with everyone. 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