Rectifiers are hardly new technology and iterations of them have been around about as long as motorcycles themselves. This week, we’ll explore how these vital pieces work and why they’re necessary. Without going into extreme detail, this post searches for the background and proper information at just what this piece of technology does and how it can make a great day sour in an instant.
What the heck is a rectifier? Also known as a regulator, a rectifier translates AC or alternating current power provided by the battery into DC or direct current power needed by the electronics on the motorcycle. Every piece of electronics on a motorcycle utilizes DC power to operate, so you can see the importance of this piece of technology. If you have a newer motorcycle with fuel injection instead of a carburetor, when the rectifier fails your bike will completely shut down because it needs the electronic message to come from the ECU to spritz the spark plugs with a shot of gas as they ignite. I found this out the hard way. My rectifier failed and it left me pushing my machine approximately 150 yards up an off ramp on a busy Interstate 80.
The Shindengen FH020AA is considered to be the best rectifier on the market.
The regulation part of the rectifier happens as electricity from the battery is pulled into the rectifier where it is throttled down to accommodate the necessary voltage used by the motorcycle. Without a proper regulator voltage can surge far above optimal levels which will overwork the stator which regenerates electricity keeping the battery from dying. When the rectifier fails, causing the stator to fail, you’re only running as long as the battery has any power. As there is no form of recharging happening, the battery is slowly dying and not being topped off. When it dies, the electronics will obviously shut down leaving you pushing that 400lb. machine up a hill.
As the rectifier processes, regulates, and converts the electricity coming from the battery it dissipates heat. Most of all rectifiers mounted on motorcycles have a series of fins to help with this heat elimination. As such, a lack of heat elimination can cause the rectifier to overheat and fail completely. It’s very important to have at least some air flow hitting the elevated fins to help with the cooling process. Many bikes have the rectifier located in a good position and it’s not much of a worry for the user. However, there have been some sportbikes that sacrifice common logic for space. For example, the rectifier on the bike that died was mounted on the frame behind the radiator which puts off heat and the engine which puts off heat. Not good.
The stator on a motorcycle generally looks like this with several groups of copper wire wrapped around posts in a circular fashion.
Rectifiers and regulators are hardly a motorcycle-only item. Everything from your car to your alarm clock has some sort of regulator inside that converts the incoming AC electricity to DC power. Almost everything that draws power has some sort of regulation system that turns AC to DC. Regulator/rectifiers are also a necessity on automobiles. It serves the same purpose here, but on cars the stator is called the alternator.