With the constant drive for efficiency and improvement, newer cars’ electrical needs have become increasingly complex.
Many components that used to be mechanically operated have become electrically powered or controlled. With this complexity, the battery charging system has become much more integral to a vehicle’s lifeblood and ensuring that all these components run correctly.
This article will dive into the causes of charging system failures.
But to do so successfully, we must first answer a few questions.
What is a Car Battery Charging System?
In short, it is the system to generate, store, and spread the electrical energy used by the many components in the vehicle, comprising two main components.
The battery and alternator.
The alternator generates constantly used electricity, and the battery stores this energy. The alternator is powered by the vehicle engine using the serpentine belts, sometimes called the fan belt running around a series of pulleys on one end of the motor.
This belt is turned by the crank pulley located on the crankshaft, which turns due to the internal combustion of the engine. This, in turn, rotates the alternator pulley changing mechanical energy into electricity.
Because of the speed at which the alternator is directly fixed to the engine RPM, the output of the alternator has to be regulated so as not to overcharge the battery.
How is this done?
Well, it’s done by the regulator, which varies the magnetic field produced by the rotating center of the alternator, known as the rotor.
In short, it changes how efficient the alternator is at creating electricity, from very efficient at low revs(revolutions of the engine) to low efficiency at high revs keeping the output power relatively constant between 13v and 14.5v
Learn How an Alternator Works:
The battery is a plastic cast container that stores this power in chemical form. Its primary purpose is to start the vehicle. Three types of batteries are used in vehicles, each being more expensive and longer-lasting.
Batteries come in different sizes for different vehicles. They are rated on their ability to produce a certain amperage or current of electricity. A good example is that of a gasoline vehicle compared to diesel. Diesel motors generally require more current to start than gasoline motors of the same size, meaning the diesel motor would need a bigger battery.
Causes of a Charging System Failure
Charging System Malfunction: Loss of Power
Loss of power can be described as anything that draws power when the vehicle motor is off(not generating power), like the headlights radio, air conditioning system, or that sneaky glove box light that stays on.
Some components can do the same while the motor is running, drawing too much electrical power like aftermarket radio systems. Both of these can draw the battery charge too low to be able to start the vehicle again
Faulty Electronic Control Unit (ECU)
ECU manages the electrical system of a vehicle making sure it runs within specified tolerances; if the ECU fails or isn’t working properly, it won’t keep these components running correctly or at all. The alternator is one of these components that needs information on electrical supply and demand requirements.
ECUs are possible causes for charging system failure, but you would want to rule out the other possibilities first, as it can be the hardest and most expensive to rectify. A scan using an OBD II reader will read these trouble codes, and some allow you to see life reads out of the alternator charging voltage. Incorrect jump-starting procedures can damage the ECU.
Dead Battery (not Charging)
The main function of car batteries is to store the power used to start the engine. This means even if you have a properly functioning alternator, your vehicle won’t start if the battery is dead. Dead batteries can be caused by a bad alternator, undercharging, or overcharging the battery.
Another contributing factor to a dead battery can be dirty loose, or damaged battery terminals causing a bad connection. Using a multimeter, you can test battery power. Multimeter set to 20v dc, turn headlights on.
Voltage should be around 12.5v(no 10 volts does not mean your battery is 80%). 12.3v is around 75%, whereas 11.8v is less than 25% charged. Be mindful of the outside temperature, as this will affect a battery’s effectiveness.
Bad Alternator (not Charging)
An alternator is considered bad when it doesn’t do its job: to generate enough electrical supply and keep the battery charged sufficiently. A healthy alternator generally generates between 13v and 14.5v.
As the battery can only store so much energy, the alternator is supposed to carry the electrical load during normal vehicle run time.
If the voltage drops below a certain level, the electrical components will malfunction. You will need a multimeter to test an alternator’s voltage output.
An alternator is bad if it has the following:
- A bad voltage regulator
- Failing/seized rotor bearings.
- A short or bad electrical connection in the magnetic windings.
- The brushes have worn out.
- The fusible links are burnt, blown, or corroded.
Some alternators are costly as they are mated to a vacuum pump that powers the brake booster. Rebuilding the alternators can be a viable option, especially for these more expensive alternators.
Worn or Broken Belts (Causing Charging System Failure)
The alternator relies on the power of the motor to turn. An alternator won’t turn or do so slowly if it has a worn drive belt. A common wear is hardening or glazing of the fan belt, causing it to slip.
A slipping belt could be caused by a faulty or loose fan belt tensioner or worn bearings on other pulleys too.
Wiring
As wiring connects the battery and alternator, damaged wires can cause voltage loss. The same thing is true of dirty terminals. Bad ground connection can also contribute to poor charging and discharging.
Check out this video:
FAQs
How can a charging system fail to be fixed?
If the alternator is bad you can replace it with a new one or have it rebuilt. If there is a bad connection or damaged wire, replace it. If the glove box or trunk light keeps burning, it can be a faulty switch that needs to be replaced.
What Exactly Does A Service Battery Charging System Mean?
When the ignition system is turned on, the light will light up to show that it’s operational, but once the vehicle is on and the alternator is charging it must turn off. If it stays on, inspection will need to be done to narrow down what is causing the fault.
Before spending a ton of money on replacing parts, check the wiring on the alternator because if it’s loose, it can give a false reading of the ECU.
How can you identify a charging system failure or problem?
Identify the symptoms
First, visually inspect the battery, checking for corrosion or loose wires. Check the alternator for loose wires. Also, check for water or oil leaks directly onto the alternator (yes I have replaced an impossible-to-get-to alternator to find out that the thermostat was leaking on it and causing it to malfunction).
If the alternator isn’t charging, you might notice warning lights on your dash. Or you might notice your radio screen is flickering, the electronically assisted steering is heavy, the automatic transmission is shifting hard, and dimming lights are. This will gradually get worse as the power in the battery gets less.
If you have a multimeter with the motor on, carefully test the alternator’s output voltage. This should be between 13 and 14.5 volts. It should stay within this tolerance even if the motor is revved.
Check the fusible link and alternator fuse if it isn’t charging. If the fuses are fine but still no charge the brushes or rotor inside the alternator needs to be replaced. If it goes outside these parameters, the regulator has failed.
Check the wiring
With the motor still running, measure the battery terminals. The power should be very similar to what you measured at the alternator, not more than a 0.20v drop.
If it drops more than that, the wiring feels warm, or the plastic coating is brittle, the cause can be damaged wires. Another culprit is the grounds (wires that are mounted to the vehicle body), which should be tight and free of corrosion.
If the wiring is fine we move onto the battery. The terminals should be free of build-up and tight connections. The battery shouldn’t feel overly warm. Carefully measure the battery voltage with the headlights on. It should be around 12.5v.
If you do not have a multimeter, do the following:
Did the vehicle die while driving?
This could be a sign the alternator isn’t charging correctly.
Does the vehicle die after jump-starting it, and the alternator isn’t charging?
Both these scenarios check the fuses and wiring, especially that on the back of the alternator.(once the vehicle is started, you can disconnect the battery, and the vehicle should keep running, but this is a risky test because if the alternator is overcharging or the rotor is damaged, it can cause a spike that may damage the electronics. You have been warned!)
After you jump-start the car, does the vehicle drive for more than half an hour, even with electronics like radio and AC? That’s a sign the alternator is operating. If not, you have a faulty alternator and need to have it tested.
If you notice the headlight, dash, or interior lights change from dim to bright the faster the engine turns, that is a sign the regulator on the alternator is faulty.
This can lead to overcharging, damaging the battery wires, and causing a sour smell in the vehicle. In case of an emergency or being stuck in the middle of nowhere, you can drive home if this happens. You can keep the vehicle RPM low if it’s more than a few miles.
Test the battery by turning the vehicle off after driving for half an hour and starting it immediately again; if it starts quickly, the battery is fine. If the car struggles to start, the wiring or terminals can be loose, dirty, or faulty. If the wiring is fine you require a new battery.
Is there a weird sound coming from the alternator or serpentine belt?
It could be caused by a slipping belt on the pulley or the bearing on the rotor seizing. It usually gets worse as you rev the motor. Also, check the tensioner, which can cause the belt to slip.
Is there a strange smell?
A strange smell from the alternator can be from overheating. Strange smells from the battery compartment point to an alternator overcharging, heating up the battery.
Either way, the regulator needs to be replaced.
It is important to remember that if the charging system fails, it doesn’t necessarily mean you are stranded.
What is a charging system’s requirement?
Can a defective battery lead to a malfunctioning charging system?
Final Thoughts
Seeing the dreaded dash warning light can cause fear of an expensive repair bill.
Here is some good news, though, not all charging system problems are expensive fixes.
Sometimes a keen eye can identify a loose wire that will only take a few minutes to tighten. Even if you aren’t a mechanic, you are now armed to identify the root cause of the charging system failure light. This gives you the peace of mind to travel to a safe spot and not worry the vehicle will explode.
