How To Excite A Generator With A Battery? Step-by-Step Guide

A generator converts mechanical energy to electrical energy through the spinning of its rotor. Normally, the rotor rotates in a magnetic field set up within the machine. Generally, the rotor powers up because there’s always a residual magnetism that supplies the required voltage for its start-up.

However, some conditions can lead to the loss of this magnetism. In that case, you should know how to excite a generator with a battery to regain its residual magnetism and operate again. This simple process demands connecting a 12 Volts battery to the generator’s exciter field.

This process, however, can get quite tricky if you’re not too familiar with different generator parts. Fear not, because this article offers you a step-by-step on how you can manually excite a generator and why you would need to it in the first place.

What Does Exciting A Generator Mean?

Exciting a generator uses an electric current to generate a magnetic field in the generator. Establishing this magnetic field within the generator helps to propel the engine to function and produce the needed electricity.

What Does Exciting A Generator Mean

Wondering what a magnetic field is? Well, magnetic field refers to the region where the magnetic properties of a moving electric charge or a magnet holds some influence.

Usually, an electric generator has a rotor that rotates in a magnetic field, either produced by field coils or permanent magnets. If the generator has field coils, the normal functionality will require a current flow within the coils. This is what creates the magnetic field inside the generator to enable the flow of power from or to the rotor.

Furthermore, the excitation regulation of a generator controls the energy output of the generator. Also, it influences the stability of the overall electrical power of the machine.

The exciter field maintains the field winding of the generator, whether for DC or AC generators. Therefore, you can go for cheap portable generators that supply power through its performing exciter field.

Why Do You Need To Excite A Generator?

Like I said before, exciting a generator refers to creating an electromagnetic field that will enable the generator to convert mechanical energy to electrical energy. This particular practice is applicable when the generator has lost its residual magnetism.

Exciting a generator ensures that it has the residual magnetism to facilitate its starting. The process primarily controls the generator’s operations, including the exciter, machine regulation, and power system.

Furthermore, this systems could be either static or dynamic. The static system comprises potential sources and compound sources, while the rotating could be the brushed or brushless types.

Why Do You Need To Excite A Generator

Now, why would you need to excite a generator if it already has integrated mechanism to do this, right?

Before we move on to specific findings, let’s learn a little bit about how a generator actually starts.

While the exciter system operates as the power source, the machine’s source of control is the regulator. The regulator system includes the following:

  • Current control
  • Voltage control
  • Power factor control
  • Field breaker control
  • De-excitation control
  • Limiters and protection
  • Field flashing control
  • Power system stabilizer

In its functionality, the excitation system produces an electromagnetic field within the rotor. The stator contains the armature winding where the inducing electrical energy takes place. How strong the magnetic field will be is directly proportional to that of the electrical energy.

This means a strong magnetic field will induce strong electrical power and vice versa. You can adjust the strength of the magnetic field of the machine by controlling the flow of current moving to the rotor.

Reasons for the loss of Residual Magnetism

The residual magnetism is the electromagnetic field a generator needs to convert mechanical energy to electric energy. A generator may not start or produce electrical power by losing this magnetism. Hence, such a machine could never be useful.

That’s the basic idea. But now, let’s dig a bit deeper!

The field winding of the exciter is in the stator, while its armature winding is in the rotor. Therefore, with the spinning of the rotor for an AC generator, the stator DC will automatically induce a 3-phase AC into the rotor winding. Subsequently, a diode, transistor bridge, or thyristor within the rotor will rectify the current and push it off through the power outlet.

But when the exciter field is not functional, the residual magnetism of the generator will be lost. Hence, your generator can’t power or produce current and need an exciting process.


Here are some of the causes for a machine’s loss of residual magnetism. In other words, why you would need to excite a generator.

A Long Idle Period

Using a generator frequently will enable the functionality of all its components. As the generator is always operational, the excitation systems will normally create an adequate electromagnetic field within the rotor. This maintains its level as long as the machine works and supplies constant electric power to appliances. Also, its effectiveness is guaranteed.

The frequent usage of the machine will ensure that there is always residual magnetism for starting the generator against the next use. But when you leave the generator unused for a long period, it losses its residual magnetism and fails to startup.

Moreover, it can’t create a new magnetic field as it would have done when it’s fully operational. So the only option for you to bring the machine to life is through exciting possible with a battery.

Reverse Connection of the Exciter Field Leads During Exciting

When you always have a constant power supply, you may not use your generator as frequently as you ought to. So, you are likely to have to flash your machine.

In addition, making a wrong connection of the exciter field leads to a 12Volts battery will cause the loss of the generator’s residual magnetism.

How to Excite A Generator With A Battery?

The use of a battery to excite a generator comes from injecting electric current via carbon brushes. This ensures that the spinning rotor of the generator undergoes a flexible excitation to produce the required magnetic field that will power the machine.

How to Excite A Generator With A Battery

As you know, generators work by converting mechanical energy to electrical energy. So, what happens when this process fails? Like I said before, in this case, you can use a battery. But how to excite a generator with a battery?

Steps Of Exciting A Generator With A Battery

The steps below tell you how to excite a generator with a battery

1. Discover the exciter field leads

You will need to find the exciter field leads first. Then, from the back of the generator, open the cover of the Automatic Voltage Regulator (AVR). This will enable you to see the leads F+ (red wire) and F- (white wire). Then, remove the leads from the AVR. This will prevent the destruction of the regulator during the exciting process.

2. Connect a 12 Volts battery, and the exciter field leads

While making the connection, you must be meticulous to avoid incorrectly swapping the exciter field leads. The connecting process is simple, and you should do that when the generator is off so that you don’t get shocked by the current.

So, you should connect the F+ lead to the battery’s positive terminal. Similarly, the connection of the F- lead should be to the negative terminal of the battery.

3. Keep the connection for a few seconds

After connecting the exciter field leads and the batteries properly, allow the connection to stay undisturbed for some time, like 30 seconds. Then, disconnect the field leads and put them back to the AVR of your generator.

By now, the generator would have been excited enough to restore the residual magnetism. Also, you can check the voltage of the generator with a voltmeter.

4. Turn on the generator

Once you confirm the voltage of your generator, you can turn it on. This shows that the exciter field has been charged with an adequate internal current to maintain its residual magnetism. At this stage, the generator can produce an electric current to power any of your desirable appliances.

How to Prevent the Loss of Residual Magnetism?

Follow the steps below to prevent your generator from loosing it’s internal magnetism:

Operate your generator frequently

You should frequently operate your generator. This will ensure that the generator never loses its residual magnetism. Also, it will help to constantly create an electromagnetic field that will enable the machine to seamlessly convert mechanical energy to electrical energy to power your appliances.

Moreover, always power off your generator before disconnecting the appliance that you connected to it. This will help to prevent backfiring from the generator and sudden breakdown.

Connect the exciter field leads correctly

The exciter field leads have the F+ and F- that you must correctly connect to a 12V battery during the exciting of your generator. The proper connection of these field leads will ensure that the machine has its residual magnetism. You should connect the F+ lead to the positive terminal of the battery while the F- goes to the negative battery terminal.

Final Thought

A generator is a machine that operates by converting mechanical energy to electrical energy. Of course, this could only be possible when there’s an electromagnetic field created in the generator’s rotor to facilitate the energy conversion. But this residual magnetism could be lost, and the generator will cease to start up.

Going through this article takes you on how to excite a generator with a battery when there’s a loss of residual magnetism. First, however, you must ensure that you’ve made the right connection between the exciter field leads of the generator and the terminals of the battery. And then, it’s just a matter of seconds. Good luck!

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