How to Wire an Alternator to Charge a Battery?

Have you ever wondered how necessary it is to have a functioning alternator to charge the battery?

Here’s a big YES! You will find it necessary, and there is no doubt about it.

And you know how the alternator works? An alternator is designed to generate electricity for your vehicle’s entire electrical parts and charge the battery.

That electrical energy is produced usually by converting mechanical energy.

How to Wire an Alternator to Charge a Battery

Believe it or not, but if you plan to start the vehicle without using an alternator, then the battery won’t be appropriate enough to produce enough power needed to keep the engine running.

What’s the catch, by the way? The alternator is crucial to keeping the battery completely charged and alternating the entire current throughout the components to keep them powered.

Moreover, this detailed guide will help you know how to wire an alternator to charge a battery. It will help you get the maximum out of it.

How Will You Wire an Alternator to Charge the Battery?

Quite simply, there is a total of four wires, right? Here’s what needs to be done.

  • The first wire will come from the casing, which ultimately attaches to the battery’s negative terminal.
  • Choose from the next three wires; one is called the field wire, connecting to the positive terminal.
  • Ensure to put a primary on-off switch that’s really necessary no doubt.
  • Moreover, turn the switch on whenever starting the alternator.
  • Please turn it off while the alternator is running.
  • Leave the alternator off when it is not in use.
  • The other wires go straight to the battery’s positive terminal.
  • If it doesn’t run fast enough to spin it to generate electricity, add a resistor between the positive terminal and the field wire.

Moreover, the wire alternator’s three-wire type includes the voltage sensing wire, ignition wire, and battery positive wire. Sounds impressive, right?

  • The battery-positive wire connects reliably to the starter.
  • Besides this, the voltage sensing wire can be connected to the battery.
  • You will connect the ignition wire perfectly from the alternator conveniently to the key switch.
  • Do you know about the two small wires present on the alternator?
  • The two wires you can connect reliably to the alternators are reliably the negative and the positive cables.
  • Ensure to connect the alternators effectively to the wires.
  • And the jumper wire connects effectively to the alternator terminal and directly to the B+ terminal.

Basically, an alternator works smoothly with a battery to supply sufficient electricity to the entire vehicle components. Got it?

The interior lights, headlights, radio, and dashboard lights all depend greatly on the alternator for keeping the battery equally charged and operating the car.

  • The alternator also contains a rotor spinning whenever the engine cranks.
  • Moreover, the rotor spins durably to cause a magnetic field.
  • After that, the magnetic field will create a current feeding through the alternator to charge the battery.
  • Furthermore, the three wires will pull the power effectively through the alternator.
  • That will keep the electrical system working along with the car operating.
  • Ensure to fulfill the process correctly to get the best results.

The technology updated models come with lots of multiple electrical components; therefore, a three-wire alternator is crucial to keep the entire components running smoothly and reliably.

Moreover, there is an internal regulator that durably monitors the volts amounts running towards the battery. Sounds fantastic, right?

With time the voltage alters drastically, whether about rising or decreasing the alternator; therefore, the regulator will cope with the situation by decreasing and increasing the alternator output, thereby maintaining a steady flow of voltage reliably to the battery.

And you know what? Alternators have one wire offer an external regulator means that you can replace the regulator when it’s broken.

In the recent alternator models, mechanics work to replace the entire alternator, especially when the regulator wears out or malfunctions completely.

Causes of why an Alternator is not Charging the Battery

Many people are confused about where electrical dysfunction begins in their vehicle. It is quite easy to diagnose such problems and fixes the errors to get reliable results.

Here is a guide to the five most common causes why an alternator is not charging your battery.

Computer Error

Many people drive cars made during the last 25 years, right?

These newly designed cars feature an engine control unit or a computer system to operate the entire vehicle’s parts and components.

Digging a little deeper! The computer also manages the alternator. Therefore any computer error leads to the malfunctioning of the alternator and prevent.

Wiring Issues

You will find lots of wiring components in the vehicle to produce power, especially for the alternator.

There are several wiring parts in the vehicle helping to produce power for your alternator when planning to charge the battery.

It only takes one wire to get disconnected or cut the power-producing malfunctioning of the alternator.

You will need to replace the wire or repair it to allow the alternator to charge the battery.

Bad Battery or Alternator

The batteries and alternators are not perfect to last forever, and each comes with its respective lifespan. Isn’t it?

Generally, a car’s battery can last about 2 to 6 years, depending on the terrain and the usage, and how you maintain it.

To be honest, batteries are designed to last for extended periods, especially during cold environments, and are shorter during hot environments.

The alternators offer an average lifespan of 7 years, but you will find many exceptions in between.

How to Fix it Perfectly

Alternator Charging a Battery

The most evident reason why an alternator fails to charge the battery is that it goes really bad.

It is easy to test the voltage, especially by attaching a voltmeter to the battery. Ensure that the engine is off while working.

Moreover, the voltage reading needs to be at least 12 to 13 volts. And you know what? You can easily assume a problem in the battery when the reading is lower than normal.

When the battery is working reliably, start the vehicle and make it reach up to 2000RPM.

That’s a significantly valuable advantage by putting more demand, especially on the alternator.

Ensure that the decreasing voltage measuring on a voltmeter means an alternator problem you will have to fix to make it function properly.


Isn’t the alternator an effective device responsible for charging the battery to keep the car running smoothly for prolonged periods? YES exactly! You heard that right.

Despite charging the car’s battery, it is also responsible for charging boat batteries and other machinery and vehicles to run off the battery power.

Moreover, the vintage vehicles that are unrestored also include a wire alternator system, right?

The three-wire alternator is the most common alternator type in the three-wire alternator.

Once you go through this article, you will come to know how to wire an alternator, especially when you desire to charge the battery.

Give a Comment