Prevent Battery Fluid Depletion with Exclusive 6V Regulated Rectifier

What is the voltage of the battery? However, before the 1970s, many vehicles, especially mopeds and small class vehicles, were equipped with a 6V battery. However, before the 1970s, many vehicles, especially mopeds and small class vehicles, were equipped with a 6V battery. The weak point of such a 6V battery is that the battery fluid can dry up before you know it, but by simply replacing one part, the problems and worries of the electrical system can be solved at once.

How does a rectifier and regulator work and what do they do?

This 1968 Suzuki AS90, with its 6V battery housed in the center of the pressed frame, shared the same basic parts as the business model, but was equipped with sporty exterior parts and was aimed at the youth of the time. The engine is a rotor-valve 2-stroke 90cc

When the battery terminal voltage is measured, it exceeds 7V. If you increase the rotation speed, the voltage rises to 9V, but the output voltage is 6V, so the battery is completely overcharged. If this situation continues, the electrolyte will evaporate and the electrodes will be exposed, and the battery will lose its function, and the bulb of 6V specification will be broken.

In both motorcycles and cars, the engine charges the battery with electricity generated by a component called the alternator, which is then consumed by electrical components such as the headlight, blinkers and horn. The alternator is turned by the engine (crankshaft) and is mainly located at the left end of the crankshaft or at the rear of the cylinder.

The electricity generated here is alternating current that alternates between positive and negative voltage, just like the 100V that runs the appliances in your house. And the voltage generated grows in proportion to the engine rotation within the range of the alternator's capability.

If you try to output enough voltage from idling, you will generate much more voltage than necessary at high RPM. It is the same logic that the dynamo lamp of a bicycle is dim when pedaling slowly and becomes bright when speeding up.

The fact that the electricity generated fluctuates with engine speed and is alternating current is completely inconvenient for motorcycles and cars with 12 V DC batteries. The rectifier and regulator installed between the alternator and battery act as regulators.

A rectifier cuts the negative component from an alternator that alternates between positive and negative output by using the property of semiconductors that allow electricity to flow only in one direction. Also, by combining multiple semiconductors, negative components can be reversed to positive.

And the regulator controls the voltage that flows to the battery. When the engine speed becomes high, the generation voltage becomes large, and if the voltage exceeds the predetermined voltage, the alternator output is short-circuited to stop the generation, and when the battery is consumed, the voltage flows again.

In the past, the rectifier and regulator worked as independent units, but thanks to improvements in semiconductor technology, they are now integrated. Today, however, regulated rectifiers have been the norm since the late 1970s, which means that the regulated rectifier era has already lasted for nearly half a century.

6V motorcycles don't have a regulator!

Genuine AS90 selenium rectifier. The rectangular plate is coated with a natural substance called selenium. One of the two wires connects to the alternator and the other connects to the positive side of the battery.

Mopeds and small motorcycles with 6V electrical systems were left behind by this trend, and although 6V was the mainstream for small-displacement electrical systems until the 1970s, the power of 12V expanded when cell motors were installed in scooters as well. The horizontal engine of the Super Cub and Monkey was also a 6V specification until the 1970s, but by changing the alternator, the engine appearance remained unchanged and became a 12V specification.

As a whole, yes, but there was a common problem: many of the smaller models that came out during the heyday of the 6V had no regulator (although some 6V models with regulators did appear in later years). The lack of a regulator means that there is no function to control the voltage generated by the alternator.

It is not possible to charge a DC battery with the alternator's AC, so even old mopeds have rectifiers as expected. However, since there is no regulator, the generating voltage is left to the alternator.

Of course, electrical component manufacturers design alternators so that the voltage is suitable for charging a 6V battery. However, due to the characteristic that the power generation voltage is proportional to the engine speed, if you try to get enough power generation at low RPM, more than enough voltage will be generated at high RPM.

When considering how to reconcile the engine speed with the power generation voltage, the legal limit for mopeds becomes one of the criteria for decision making. Whether or not it is reasonable on public roads is another matter, but the legal speed limit for 50cc motorcycles has always been 30km/h. If the engine speed is 30km/h with the transmission in 4th gear and the 6V battery can be charged at that speed, then the necessary conditions are met. If you drive at a higher speed than that and generate more voltage than that, it is the user's responsibility.

The regulator controls the voltage and at the same time interrupts the charge according to the battery voltage, so if the electrical system is not consuming much power and the battery is in good condition, it will cut the charge.

However, without a regulator, the battery will continue to be charged regardless of whether it is hungry or full. As a result, the electrolyte in the overcharged battery will volatilize and the level will drop.

This is a problem that occurs when the electrolyte in the battery dries up and the electricity generated flows directly to the light bulb. The reason why the engine can still perform is that the ignition system of mopeds and small models is often a flywheel magneto type, and this type does not use the battery as a power source.

A 6V battery may be charged at 9V or 10V, but the output voltage is still 6V. In fact, it will exceed 6V, but a 6V battery will never output 9V or 10V. In other words, a 6V motorcycles can be said to balance the voltage by having the battery itself act as a regulator.

Stop battery fluid loss by installing a regulated rectifier

This is a regulated rectifier for 6V that is sold by some shops. It looks the same as the 12V regulated rectifier, but the circuitry inside is optimized for 6V.

The connector is a 4-pole, and in addition to the alternator and battery positive, there are two additional wires that interrupt the body ground and headlight wiring. The wiring in the image is an example of this product, so please follow the instructions for the regulated rectifier you are purchasing to find out what each terminal does.

That was not convenient, so the last stage of the 6v models came with a standard regulated rectifier. The Honda Jazz is a well-known model. And aftermarket parts makers are selling the regular rectifier for 6V.

With this component, it is possible to control the charging voltage even on older 6V models that only have a rectifier.

Here I have installed a regulated rectifier on an old 1960's Suzuki AS90 motorcycle that has a rectifier called a selenium rectifier. The selenium rectifier is just a component that converts an alternating current with positive and negative waveforms into direct current, and it has two terminals that are body grounded.

The 6V regulated rectifier has four terminals, three of which are used in the same way as the selenium (the black wire corresponds to the body ground of the selenium). The new function will be to control the headlights and tail lights which are turned on by AC. In the existing circuit, the headlights and taillights were connected directly to the alternator light coil without going through the battery. By interrupting the yellow wire in the middle of this circuit, it will be possible to prevent the headlights from being cut off by overvoltage.

If you don't like the instability of the 6V electrical system, you can change to 12V, but by improving the state of charge, the battery will not dry up and the electrical system will be stable. If you have a low voltage battery, you may want to consider changing to 12V, but as a preliminary step, you may be able to improve the situation by installing a 6V regulated rectifier.

When a regulated rectifier is installed, the voltage is intermittent according to the charging status, resulting in a stable battery voltage. The control voltage is determined by the settings inside the regulated rectifier, but the voltage is about 6.3V when idling at around 1100 RPM.

When idling, the headlight voltage is in the 5V range, and as the RPM is increased, the voltage stops rising at around 6.3V. This means that there is no chance of the filament suddenly cutting out and causing total darkness while driving at night at full throttle.

The 1968 blinker relay is old-fashioned so I replaced it with the latest 6V relay. For an out-of-print model, updating the electrical parts is only beneficial.