A Technique to Convert 6V Electrical Equipment to 12V by Simply Changing the Connections (Part 2)

The 6V electrical system of the out-of-print moped models is weak when idling or waiting at traffic lights, let alone while driving. It is the dream of every 6V moped owner to change such an old-fashioned electrical system to 12V specification like the current models. This is a dream of every 6V moped owner. In the previous article, I explained how to rewind the charge coil, but here I'd like to introduce an example where the stock 6V coil was a "miracle".

Even if you're not good with electricity, it's important to observe it at all costs.

Before the introduction of the scooter-type Passol, family motorcycles were popular as a means of transportation to shopping and school. The Yamaha Chappy was introduced with an automatic transmission for ease of operation, and later hand clutch and centrifugal clutch versions were added. It had two engines, 50cc and 80cc, and became a long-seller, sold from 1973 to 1980.

As the magnet attached to the inner surface of the flywheel rotating at high speed rotates around the outside of the charge coil and source coil, alternating current is generated by electromagnetic induction. The electricity generated by the source coil is boosted by self-inductive action when it is interrupted by the contact breaker and sent to the ignition coil. The charge coil and lighting coil are the power source for battery charging and headlight & tail lamp lighting respectively.

Some of the Sunday mechanics who love motorcycles are"I like to tinker with machines, but I don't like electricity. It seems that there are a lot of people who say "I can't do it". There is an aspect that you can get used to attaching and detaching parts that are fixed with bolts and nuts by repeating the work, but you may get confused and give up on electrical parts just by looking at the wiring.

It is true that if you want to understand all the electrical components correctly from the principle, you have to study them in a certain way. However, just by knowing some of the workings of the electricity that actually occurs in your car in front of you, such as how to connect the contact breaker of the point ignition, how to adjust the ignition timing, and how to measure and compare the control voltage after passing through the regulated rectifier with the generation voltage of the stator coil, you will come to understand the workings of each part and This will give you a better understanding of how each component works and what you need to do about it.

For owners of out-of-print mopeds, it's a common desire to convert their old mainstream 6v to 12v. I explained in an earlier post that doubling the battery voltage would allow half the current to do the same job.

When 12V and 6V are compared, 6V car needs to flow a lot of current even if the voltage is half, and the condition of the battery is important to stabilize the electric system. Of course, the role of the battery is big even with 12V, but it is a fact that the stability is higher than 6V car when the charge system is seen in total.

Whether the battery is 6V or 12V, power is generated by the rotation of magnets of different polarities around the charge coil. The coils on current cars are spread out radially inside the flywheel, but the coils on out-of-print mopeds are two or three bars in a row. Of these, the charge coil does the work of recharging the battery, and this is where the lighting coils that turn on the headlights and tail lights are often tied together.

Even if you are not good at electricity, if you remove the flywheel and observe the inside, you will see that there are two sets of coils side by side. One of these coils is the source coil for ignition, which is connected to the contact breaker in a points car, and to the pickup coil in a CDI car. So the other coil is related to the charging system. This is the case with the 1970's Yamaha family bike, the Chappy, shown here.

To distinguish between a source coil and a charge coil (which is an integral part of the lighting coil), observe the wiring connected to the coil. In most cases, the source coil has thin, tightly wound copper wire and two wires coming out of the coil, while the charge coil has thicker copper wire and multiple wires connected to it. The multiple wires are the charging system that leads to the battery through the rectifier and the lighting system that leads to the headlight switch.

The charge coil.Since the voltage generated is proportional to the number of turns of the copper wire, we can count the number of turns while unwinding the current charge coil, and if we wind the coil twice as many times, the voltage generated will be twice as high.The coil will become If the coil is too thick, it may interfere with the flywheel that is placed on top of it.

Turns out I'm only using half a charge coil.

This is the charge coil of Yamaha Chappy (1978 model). I haven't compared it with other chapys, so I don't know if all the years have this specification or this one happens to be like this, but there was an unused wire at the end of the core apart from the normal circuit. This would be used for the "green/Since the number of coil turns increases over "Red" and "Black", the voltage generated will increase with the increase. The "Yellow" of the light system also has more turns, so the voltage flowing to the lights should also increase.

The charging system of the Chappy discussed here is a standard configuration for mopeds of the 1970s, in which the current generated by the charging coil is rectified by a rectifier to charge the battery. The lighting coil is not rectified, and the power supply for lights is used as AC. For your information, the lighting coil is also used as AC in 12V moped models such as Honda Monkey and Ape. However, they use AC with the maximum voltage controlled by a regulator.

By winding two different coils around one iron core, there are generally three wires from the coil: one for charging, one for lighting, and one for grounding. If you look at the coil of CHAPI, you can see that the color of harness on the body side is "Green/Red" for charging, "Yellow" for lighting, and "Black" for grounding. However, there is one more wire on the charge coil of this chapie, which is not used for either power generation or light.

Not all moped 6V vehicles are the same, it's a rather rare case and I don't know why, but I was in a position where I could get more coil turns than the existing "black" ground by using this unused wiring.

Just by rewiring the coil, it turns into a 12V specification!

Disconnect the coupler that connects the sub-harness of the coil part to the main harness of the car body, and measure the change in voltage due to the connection of the charge coil wiring. If you observe where each wire color is connected to the coil, you can work with the actual product without staring at the wiring diagram. In other words, you don't need to be afraid of electricity.

The "green/red" that rises from the charge coil does not pass through the rectifier, so the voltage is measured in AC mode. The car is originally a 6V electrical car, but just by reconnecting it, 12V is being generated. This is at idle, so it will rise even more if the engine speed is increased. Why didn't they use a coil with this capability back then? 

Lighting coil in idling state. The voltage is lower than the charge coil because it has fewer turns, but it still generates more than 8V. If you increase the RPM, you can get more than 10V, so you can use 12V headlight bulb.

This is a 12V regulated rectifier used in small displacement vehicles, most notably the Honda Monkey. It is designed for single-phase AC generation with only one charge coil, which is common in the moped class. For alternators with three-phase AC power generation for medium-sized vehicles and larger, use a regulated rectifier for three-phase AC. When the charge coil wiring is connected to white, the AC is converted to DC, the voltage is set to 12V, and then output from red. Red is connected to the battery. When the lighting coil wiring is connected to yellow, it controls the voltage to 12V as AC, and interrupts the headlight wiring. Black works by grounding it to the car body.

I wired up the regulated rectifier and installed a 12V battery, started the engine and measured the voltage, it stopped at mid 14V, confirming that it was working correctly. At this time, the charge current was 1.It was about 2A, so it has enough power generation capacity to charge a moped class battery.

The brightness of the headlight changes according to the engine speed because the headlight that lights by the alternating current doesn't get the power supply from the battery. When the engine is idling, the brightness is about 6V, so it is darker than 12V bulbs, but when the engine is running, the brightness is over 10V, so it is practical for both night and day. If you want to increase the voltage with AC lighting, you can re-wind the lighting coil, or you can use the battery to light the lights as I mentioned before. It's easy to get confused when you think about it, but with the small displacement cars of the analog era, there are many things that can be done.

So I connected the "black" wire on the body side to the extra wire at the end of the charge coil, and it turned out to generate 12V AC from the idling speed. The lighting coil that is integrated with the charge coil is just under 6V, so it's not enough for 12V headlight bulbs, but if you open the throttle, it goes up to over 10V, so it's bright enough for 12V bulbs.

Once you know you can get 12v without rewinding the coils, the bodywork will need to be modified to match. In addition to converting the battery, indicator relay, headlight and indicator bulbs to 12V, we will also be adding a regulated rectifier. the stock 6V circuit has a rectifier that converts AC to DC, but it does not have a regulator to control the charging voltage. This is because the 6V battery itself is used as a regulator while the maximum voltage is determined by the number of turns of the charge coil, which is a unique component configuration for the small displacement moped class.

To charge a 6V battery, it is obvious that the voltage must be higher than 6V, but if the voltage is excessively high, the battery will be damaged. However, if the voltage is too high, the battery will be damaged. The regulator is installed to prevent this, but it is not a problem as long as the charging voltage is not so high as to damage the battery.

However, if we go back to the beginning here, if this chapie has not only a rectifier but also a regulator, it would be possible to use the charge coil which can generate more than 6V from idling. The voltage regulator was equipped, and furthermore, in the next year, the change to increase the amount of charge was added though it was 6V specification. The American type Honda Jazz 50 that appeared in the late 1980s also had a 6V electrical system, but the charging system was a regulated rectifier.

Even if it is a model before such an improvement is given, it is possible to change to 12V specification only by changing the wiring. Specifically, it is used in each Honda car including the 12V specification Monkey, and uses the 4 pin type that is sold as a general-purpose part.

To connect the wiring between this regulated rectifier and the chappy's charge coil, connect the "green/red" of the charge coil to the "white" of the regulated rectifier, the "yellow" of the charge coil to the "yellow", the "red" of the regulated rectifier to the battery, and the "black" to the car body ground. With just this much wiring, the battery charge voltage will be controlled at a maximum of 14V, and the headlights and tail lights will be on at 12V AC.

It would be so much easier if you can convert any 6V car to 12V by just rewiring, but unfortunately, most of them need to rewind the coil. However, if you rewound the charge coil and lighting coil at the same time and use DC for the charge system and AC for the lighting system, you can use a general-purpose regulated rectifier.