Car alternator charging system. CHARGING SYSTEM DIAGNOSIS

Charging System | Components. Function. Working Principle. Diagnosis Tips

Vehicle is equipped with many electrical devices to drive safely and comfortably. The vehicle requires electricity not only while driving but also while it stops.

Therefore, the vehicle has a battery for a power supply and a charging system to generate electricity by the engine running. The charging system supplies electricity to all the electrical devices and charges the battery. The Charging system is an important part of the electrical system. It provides electrical current for the lights, the radio, the heater, the engines electrical systems, and other electrical accessories. It also maintains the batteries in a charged state, recharging them as necessary.

The charging system has three main components: the alternator, the voltage regulator, and the batteries.

alternator, charging, system, diagnosis

The alternator generates electrical power to run accessories and to recharge the batteries. It is normally driven by a belt located off the crankshaft. Mechanical energy from the crankshaft is converted by the alternator into electrical energy for the batteries and accessories. The voltage regulator acts as an electrical traffic cop to control alternator output. It senses when the batteries need recharging, or when the vehicles electrical needs increase, and adjusts the alternators output accordingly. The batteries are a reservoir of chemical electrical power. Their primary purpose is to crank the engine. They also supply power to vehicle accessories when the electrical load is too great for the alternator alone.

Three-phase alternating current

(1) When a magnet rotates within a coil, a voltage will be created between both ends of the coil. This will give rise to an alternating current. (2) The relation between the current generated in the coil and the position of the magnet is as shown in the figure. The largest amount of current is generated when the N and S poles of the magnet are closest to the coil. However, the current flows in opposite direction with each half turn of the magnet. Current that forms a sine wave in this manner is called “single phase alternating current”.


In general, the components of the charging system are composed of alternators and regulators. However, the charging system needs to add some additional components so that the electricity generated can be supplied to the battery and to all electrical loads safely and precisely. The component, consisting of;

1. Battery

The function of the battery is as a storage of electrical energy. Like a warehouse, the battery will store all the electrical energy generated by the alternator and then this stored electricity is removed when necessary.

2. Fuse and Fusible links

Fuse and fusible links have different functions even though have the same shape. Fusible link can be called as main fuse which is placed near the battery positive terminal. The function of this fuse is to protect the entire electrical system of the car from excessive currents. Generally the fusible link has a capacity of up to more than 60 Ampere. While the function of the fuse is as a safety of a series of specific electrical wiring, in conventional charging system there are two fuse with same capacity (its about 10-15 Ampere). A fuse is used as a voltage regulator fuse and another fuse is used to secure the CHG and Voltage relay. 3. CHG Lights CHG lamp or commonly also called “charging warning light” is an indicator light to indicate the presence failure of charging system. When the ignition key ON then this light will light up normally, as well as when the engine life of this lamp should turn on, if it is dead then it could mean the charging system failure. 4. Ignition key The ignition key works as a switch. The charging system will be activated automatically when the engine is running, but to generate a magnetic field on the rotor coil must be done by a switch. Ignition switch is used as a switch to connect anddisconnect power (positive battery curents) from battery to rotor coil. When the ignition key is ON, then the electricity from the battery to the coil rotor will be connected. However, when the ignition key is turned OFF then the power supply will be cut off. So it is not possible the altenator generates electricity when the ignition key is OFF even the engine crankshaft is rotate. 5. Regulator The function of the regulator is to regulate the voltage generated by the altenator. Why should it be there? because the voltage generated by the altenator depends the engine’s RPM. This means that if the engine RPM is low, the altenator voltage is also low, but if the engine RPM is high then the altenator voltage is also high. The regulator will be used to keep the voltage generated by the altenator not exceeding 14 volts even if the engine run in high RPM. This voltage setting aims to protect the electrical components of the vehicle to prevents over-voltage. There are two types of regulators, namely type or conventional type and type of IC. The point type/conventional uses two coils to adjust the altenator’s output voltage. While the IC Regulator uses an IC circuit (Integrated Circuit) to regulate the output voltage. 6. Altenator The function of the altenator is to convert a partial engine’s rotating energy into electricity. The altenator input comes from the engine pulley connected through a V belt, the rotation of the rotor will cause the intersection of the magnetic force line with the stator coil so that the electrons flow on the stator coil. The electricity in the stator coil is not directly connected to the battery, but it must pass through the diode bridge to rectify the current. This is done because the current in the stator coil is AC (Alternate Curent). 7. Charging Wires The function of charging wires are to connect every component of the charging system, there are at least two types of wires: standard wire and B wire. The standard wire has a small diameter like the car’s electrical wiring in general, the function of this wire is connecting each terminal on the entire charging system. While the B wire has a larger diameter than the standard wire and almost matches the stater wire. The function of this wire is to connect the terminal B altenator with Battery.


Flow of electricity in charging system Electricity in each position of the ignition switch. Ignition switch ACC or LOCK Ignition switch ON (when engine is not running) When the ignition switch is in the ON position, current flows from the battery to the alternator. The reason for this is as follows. The alternator generally used for the vehicle generates electricity by rotating the magnet. The magnet is not the permanent magnet but the electromagnet that generates magnetic force by flowing electricity inside. Therefore, it is necessary to supply electricity to the alternator before starting the engine to prepare for generating electricity. Ignition switch ON (when engine is running)

The alternator plays a major role in the charging system. Alternator has three functions of generating electricity, rectifying current and regulating voltage. (1) Generation Transmitting the engine revolution to the pulley via the v-ribbed belt turns the electromagnetized rotor, generating alternating current in the stator coil. (2) Rectification Since the electricity generated in the stator coil is alternating current, this cannot be used for the DC electric devices installed on the vehicle. To use the alternating current, the rectifier is used to rectify the alternating current into direct current. (3) Regulation of voltage IC regulator regulates the generated voltage to make the voltage constant even when the alternator speed or the amount of current flowing into the electric devices change.

Why a Mastervolt alternator?

Mastervolt Alpha alternators are specially designed for ships and professional mobile applications to provide sufficient power even with a low rpm. A pulley ratio of 1:3 and an engine idle speed of around 700-800 rpm will generate substantial current for charging the battery sets and powering the connected equipment. Mastervolt alternators are also resistant to the high temperature of the engine room, allowing the engine to serve as the energy source for onboard consumers and as a quick charger for the service batteries.

Make sure you do not choose your alternator too small. A larger one will ensure that the battery is charged faster and engine hours are kept to a minimum – we suggest choosing an amperage between 30 and 50 % of the battery capacity.

The standard alternator designed for road vehicles has a voltage regulator mounted to the back of the alternator and set to a single charge voltage of 14 or 28 volt. This is sufficient for a car battery, which is rarely (if ever) discharged. Furthermore, the voltage regulator of an automotive alternator is often temperature sensitive and in high temperatures regulates the voltage even further down, often to 13.5 or 26.5 volt. This is much too low for sufficiently recharging a discharged battery. The maximum achievable battery capacity for these voltage levels is around 60 to 70 %. The lifespan of a battery is significantly lower if it is never properly charged. In order to adequately recharge a partially empty or completely flat battery at 25 ºC, voltage need to be 14.25 volt for a 12-volt battery and 28.5 volt for a 24-volt one. Once the battery is 100 % full, this voltage must be reduced to 13.25 or 26.5 volt (float phase) to prevent the batteries from becoming overcharged.

Ungrounded – also for aluminium vessels

Mastervolt alternators are delivered ungrounded, i.e. the negative pole of the alternator is not connected to the alternator casing but has a separate connection. This means that they are also suitable for aluminium boats, where the negative needs to be separated from the hull.

Mastervolt alternators offer a much higher output than the alternators supplied with engines. As a result, the standard single belt is insufficient to transfer the power from the engine to the alternator. Two belts are required and the pulley of the engine will often need to be changed as well. Your engine supplier can help you choose an appropriate double pulley and give advice on setting up the alternator. In order to handle the high output you will also have to adjust the alternator support.

Benefits of the Alpha Pro charge regulator

Alpha Pro charge regulator, supplied with a Mastervolt alternator as standard.

How Alternators Work to Make Electricity

The alternator is comprised of a voltage regulator and three main components: The stator, rotor, and diode. When the battery initially powers the car, the alternator belt, or V-belt, spins the pulley on the alternator, causing the rotor inside the alternator to spin very quickly. This rotor, which is basically a magnet or group of magnets, is situated inside a nest of copper wires, which are called the stator.

The process whereby electricity is generated by spinning magnets at incredibly fast speeds along a set of copper wires is called electromagnetism. The electricity harnessed this way is conducted through the copper wires to a diode, which changes the electricity from AC to DC, the current that the car battery uses.

The next step happens within the voltage regulator—a built-in component on modern alternators—which is basically a gatekeeper that will shut off the flow of power to the battery if the voltage goes above a certain level, usually 14 and a half volts, which keeps the battery from getting overcharged and burning out. As the car battery is drained, current is allowed to flow back into it from the alternator, and the cycle goes on and on.

Signs of a Bad Alternator

When a car alternator is going bad, drivers will notice a reduced capacity for electrical use, often resulting in things like dim headlights. But these clues won’t last long, because a partially charged battery usually has enough power to operate things like headlights and power Windows, but will fail the next time you try to start the vehicle.

There is also usually a dash board light, also known as the battery light because it’s often shaped like a little battery, that will alert drivers to an alternator that is not providing enough charge to keep the system up. Concerned car owners can also check the charging system, or take the car to a mechanic if they are experiencing any sort of electrical issue.

Alternators 101

Many people don’t think about their alternator until it goes out, but it has a pretty important job sitting under the hood. The alternator is a small electrical generator that provides electricity to your car by converting mechanical energy to electrical energy. The alternator provides current to the spark plugs, lights, A/C, sound system, and more. For a car part that is about the size of a loaf of bread, the alternator does a lot of work.

What Does the Battery Do?

So, at this point, you may be thinking, I thought the battery did all of that! Actually, the battery really only has two jobs: powering electronics when the vehicle isn’t running and starting the engine. Once the engine starts, the alternator takes over and supplies the electricity that your vehicle needs.

If you had to rely on your battery to run your car, you would only get a few miles down the road. Anyone that has had an alternator go out on them knows the feeling as you see your lights begin to dim and you lose power to your engine, with it finally stalling out. It doesn’t take long once the alternator quits for the rest of the vehicle to also shut down.

If the alternator is working correctly, it not only supplies power to the vehicle, it also sends voltage to the battery to charge it. Most batteries have a voltage of around 12 volts, whereas the alternator’s output is between 13 and 15 volts.

alternator, charging, system, diagnosis

How Does an Alternator Work?

Earlier we said the alternator was a small electrical generator, but what does that mean? The alternator is pretty simple in its construction: a voltage regulator, a stator, a rotor, and a diode. That’s it. When the engine is running, a belt turns a pulley on the alternator, causing the rotor to quickly spin inside the alternator. The rotor is made up of a magnet or group of magnets and is inside a stator, which is a nest of copper wires.

The magnets spinning inside the copper wire creates electricity through electromagnetism. The electricity that is created is sent to the diode which changes the current from AC to DC, the current used by the car battery and the rest of the vehicle.

After this step, the voltage regulator steps in. The voltage regulator shuts off the electrical flow to the battery if the voltage gets too high. If the battery is overcharged, it can burn out. As the battery voltage lowers, the regulator allows the current to flow back to the battery, helping it maintain a useful charge.

alternator, charging, system, diagnosis

Does an Alternator Replace a Charger?

An alternator cannot do everything a charger can. For starters, an alternator can charge a battery with a low charge, but it cannot charge a dead battery. As we said above, the battery’s job is to start the engine and then work as an electrical load balancer. The alternator runs the electrical system of the vehicle from the engine to the wiper blades to the seat warmer, while keeping the battery topped off.

Most vehicle batteries are full at 12 volts, but if the voltage drops to just under 10 volts (less than a 20% loss), the alternator won’t be able to keep up on charging it and the battery’s cells can be damaged. If the alternator can’t charge a discharged battery, it definitely can’t bring a dead battery back to life.

Some people think that they can just drive around and recharge their battery, but this isn’t the case. In most instances, it will only provide a surface charge to the battery, which is pretty much worthless. In worst-case scenarios, the alternator can be damaged or even completely destroyed. This is why it is important to invest in a CTEK Smart Charger.

If you have to constantly charge the battery, either your alternator or your battery is about to die. It’s important that you fix the problem before you are stuck with a car that won’t start or run.

alternator, charging, system, diagnosis

A Battery Charger Keeps Your Battery Healthy

When you use a CTEK Smart charger to charge your vehicle’s battery, you not only charge the battery, but the charger will also test the battery and rehab it if it is damaged. When your battery goes through the desulphation process with a CTEK charger, it can extend the life of your battery 2-3 times. Most batteries last 3-5 years, so you can see what a benefit this can be.

When the battery is attached to a CTEK Smart charger, the battery will be run through a 4 to 8 step charging process. The charger will monitor the battery throughout the process, making sure the right step is being used: desulphate, revive, charge, condition, and maintain. By having a healthy battery in your vehicle, you will save yourself stress from having a dead battery, avoid the cost of buying a battery and having your vehicle towed, and keeping more batteries out of the landfills.

A CTEK Smart charger is designed and engineered to allow you to set and forget it for months without harming the battery. You don’t have to worry about connecting it wrong or being injured by a spark. The Smart charger will tell you if it’s connected wrong and will protect your battery and the Smart Charger won’t spark no matter what. All of the CTEK products are easy and safe to use for every level of expertise.

Use our Charger Selection Tool to find out which CTEK charger is the right fit for your vehicle.

Contact us today to learn more about our line of Smart chargers and find out which one is best for you. We look forward to doing our part to keep your vehicle running well.

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