A rectifier is an essential component in the charging system of a motorcycle. Along with the alternator and the battery, the rectifier forms the core charging system in bikes. The charging system is used to run several electric accessories in a motorcycle and hence, plays a vital role including starting the motorcycle.
So, will a motorcycle start with a bad rectifier? A rectifier converts alternating current (AC) to direct current (DC) to charge the battery. A bad rectifier results in the battery not charging up and hence, will drain out its charge eventually. Since motorcycles require battery power to start them up, a bad rectifier will eventually result in the motorcycle not able to start.
Before deep diving into why a motorcycle won’t start with a bad rectifier, let us understand the function of a rectifier in motorcycles.
What Rectifier Does in a Motorcycle
A rectifier is an electronic device which converts alternating current (AC) to direct current (DC). Alternating current is the current that reverses its direction periodically, whereas direct current flows in only one single direction.
Since the electronic device “rectifies” the direction of the current to flow in a single direction, it is called a rectifier.
Now, what does this rectifier do in a motorcycle? The same function it does in every other device. In a motorcycle, when the engine is running, there will be an alternator which generates alternating current (AC) in the system.
In motorcycles, the rectifier is also coupled with a regulator to moderate the voltage coming from the alternator. So, whenever a rectifier is mentioned in a motorcycle, it usually refers to rectifier-cum-regulator. The same applies whenever a regulator is mentioned in context to motorcycles.
This alternating current generated by the alternator is passed on to the rectifier/regulator which converts the AC into DC (direct current).
The direct current, converted by the rectifier, is then passed on to the battery. the battery will store this charge for motorcycle usage requirements.
Together with alternator and rectifier, battery forms the charging system in the motorcycle. Whenever the electronic accessories in the motorcycle like – headlight, starter, indicators, brake light, horn etc. – require electric current, the battery supplies the charge.
In short, the alternator generates AC using the energy generated form the engine. Rectifier converts this AC into DC. And battery stores the charge from the DC.
Role of the Rectifier in Starting Motorcycle
Now that we know what a rectifier does, it is still not clear how a rectifier is involved in starting of the motorcycle.
So, what exactly is the role of a rectifier in starting a motorcycle? While there is no direct connection between the rectifier and motorcycle starter, most modern motorcycles require battery charge to start them up.
While the alternator in a motorcycle generates AC, the rectifier converts this AC into DC. The converted direct current finally passes on to the battery and is stored inside.
Essentially, the motorcycle requires battery charge to start every time. And battery requires alternator and rectifier to get charged.
A bad rectifier or an alternator means the battery won’t get charged up. And a battery with no charge equates to a motorcycle not being able to start.
Since the battery itself is charged up with the help of alternator and rectifier, a bad rectifier will invariably cause starting problems.
For more info, here is our post detailing the rectifier functions.
A Bad Rectifier Won’t Charge the Battery
As discussed in the previous sections, the battery in a motorcycle requires both the alternator and the rectifier to work properly.
If the alternator is not working, there will no power generation at all. As a result, the battery won’t be charged up.
If the rectifier is not working, the generated alternating current (AC) from the alternator is not converted into direct current (DC). This, again, leads to battery not storing the charge since the battery requires direct current (DC).
In both these cases, where either of the two, alternator or rectifier, is not working, then the battery won’t be charged.
And when the battery is not charging up, the remaining charge in the battery will soon be used up by the different electronic accessories including the starter motor and eventually, the battery will die out.
Once the battery dies out, the motorcycle which requires the battery charge to start up, will not be able to start.
Eventually, a Motorcycle won’t Start with a bad Rectifier
As discussed, a bad rectifier results in the battery not being able to charge. And motorcycles, at least most modern motorcycles, require battery to start them up.
So, when the battery is not charging up, the remaining charge will soon be drained out by the electric accessories like – starter, headlights, turn indicators, injection system, horn etc.
Once the remaining charge is drained out from the battery, the battery is as good as dead now, with no charge remaining in it. Since the motorcycle requires battery charge to charge them up, a dead battery effectively results in motorcycle not able start at all.
That’s why, if there is a bad rectifier in the motorcycle, the battery won’t be charging up and eventually, once the battery drains out, the motorcycle will not be able to start.
A rectifier, essentially, converts alternating current (AC) to direct current (DC) to charge the battery. A bad rectifier results in the battery not being able to charge up and the battery will drain out its charge eventually. Since motorcycles require battery power to start them up, a bad rectifier will eventually result in the motorcycle not able to start.
Can motorcycle run without a battery? Most modern motorcycles cannot run without a battery. If the battery is at marginal health and some life still left in it, motorcycle can be started with a push/bump start. The only exception where battery is not needed to run are motorcycles with magneto ignition, which can be seen in old motorcycles, small dirt bikes and scooters.
Will motorcycle run with a bad alternator? The alternators convert the mechanical energy derived from the engine into electrical energy in the form of alternating current. Just like a rectifier, a bad alternator results in the battery not able charge. This again, will eventually result in the motorcycle not starting up.