There was a recent post in the General Discussion section that claimed to explain a motorcycle's rectifier but didn't.
Here is a simple (I hope) explanation for everyone confused by that post or just interested in the electrical charging system on our bikes. I am an electrical engineer so it may sound a little techy.
Clarification
Alternator rectifiers and the voltage regulator perform different functions. but on our bikes they live in the same module - the service manual's description of this module makes them sound like one thing.
Location
In an automotive system. the rectifiers (usually six of them) are soldered deep inside the alternator, while the voltage regulator may be removable, hidden under a cover on the back of the alternator.
In our CB500/CBR500 series bikes, the rectifiers for the alternator and the voltage regulator are housed in one module, which is mounted on the bike's chassis, not on/in the bike's alternator.
Function
The rectifiers convert the AC voltage from the alternator to an uneven DC voltage. They do not regulate.
The battery smooths the uneven DC voltage from the rectifiers into the steady DC voltage the bike needs.
The voltage regulator measures the voltage across the battery and adjusts the alternator output current to hold that voltage in a narrow range. Otherwise the alternator voltage would vary with engine speed and changes in the electrical load.
Voltage control
A fully charged lead acid battery will measure around 12.7 to 12.8 volts after sitting overnight at room temperature.
A fully discharged battery = 11.8 to 12.0 volts after sitting overnight.
However when the engine is running above idle speed, the voltage regulator applies around 14 volts to the battery. This voltage allows the battery to charge if it needs it, but does not damage a fully charged battery.
If the battery has been fully discharged, the bike's charging voltage will start off lower than 14 volts. Not sure how much but my guess is if the voltage above idle is less than 13.2 volts after an hour of riding, you have a bad battery (or, much less likely, a charging system problem).
Caution
If you disconnect a battery cable while the engine is running (even for a moment) you may destroy one or more of the alternator rectifier diodes. Same can happen with a loosely connected battery cable that loses contact with the battery terminal.
Magneto? clarifying a point in the original confusing post
There is no magneto in cars/bikes with an alternator. My 1974 motocross bike had a magneto to provide energy to the spark plug coil. There was no battery or electrical system on that bike.
Here is a simple (I hope) explanation for everyone confused by that post or just interested in the electrical charging system on our bikes. I am an electrical engineer so it may sound a little techy.
Clarification
Alternator rectifiers and the voltage regulator perform different functions. but on our bikes they live in the same module - the service manual's description of this module makes them sound like one thing.
Location
In an automotive system. the rectifiers (usually six of them) are soldered deep inside the alternator, while the voltage regulator may be removable, hidden under a cover on the back of the alternator.
In our CB500/CBR500 series bikes, the rectifiers for the alternator and the voltage regulator are housed in one module, which is mounted on the bike's chassis, not on/in the bike's alternator.
Function
The rectifiers convert the AC voltage from the alternator to an uneven DC voltage. They do not regulate.
The battery smooths the uneven DC voltage from the rectifiers into the steady DC voltage the bike needs.
The voltage regulator measures the voltage across the battery and adjusts the alternator output current to hold that voltage in a narrow range. Otherwise the alternator voltage would vary with engine speed and changes in the electrical load.
Voltage control
A fully charged lead acid battery will measure around 12.7 to 12.8 volts after sitting overnight at room temperature.
A fully discharged battery = 11.8 to 12.0 volts after sitting overnight.
However when the engine is running above idle speed, the voltage regulator applies around 14 volts to the battery. This voltage allows the battery to charge if it needs it, but does not damage a fully charged battery.
If the battery has been fully discharged, the bike's charging voltage will start off lower than 14 volts. Not sure how much but my guess is if the voltage above idle is less than 13.2 volts after an hour of riding, you have a bad battery (or, much less likely, a charging system problem).
Caution
If you disconnect a battery cable while the engine is running (even for a moment) you may destroy one or more of the alternator rectifier diodes. Same can happen with a loosely connected battery cable that loses contact with the battery terminal.
Magneto? clarifying a point in the original confusing post
There is no magneto in cars/bikes with an alternator. My 1974 motocross bike had a magneto to provide energy to the spark plug coil. There was no battery or electrical system on that bike.