Why Battery Voltage Drops When Ignition Turned On? (Fixed!)

The electrical system in your vehicle requires a stable source of power. As long as the battery has a stable voltage, the engine will turn on smoothly. But if there is a delay in the cranking or the engine doesn’t crank at all, it indicates a voltage drop.

You will learn the reasons and symptoms of this problem in detail. Plus, I will show you how to diagnose and fix the problem effectively. Let’s crank it.

Battery Voltage Drops When Ignition Turned On: What Are the Reasons?

The following reasons contribute to the battery voltage drop problem. Know about these reasons in detail.

Higher Accessory Loads

Besides crucial accessories, such as headlights, air conditioning, etc., vehicles also have music systems and screens. When you turn the ignition key, these electrical components get activated.

As a result, they put additional stress on the battery. Powering up all these electrical components at the same time can cause the battery voltage to drop noticeably. It happens even when the battery health is good. But when the battery health is low, it affects the starting process.

Starter Motor Load

When you turn the ignition on, the starter motor draws power from the battery to start the engine. It requires high amperage. In general, starter motors will draw about 200 amps when you turn the ignition on.

As a result, the battery voltage drops under load by 2-3 volts. If the battery health is good, the voltage drop may not be more than 1-2 volts. The change in voltage depends on how many amps the starter motor is drawing from the battery.

Poor Battery Health

Batteries in your vehicle are very stable when they are new. But as the battery gets older, it loses the voltage stability. If the battery is too old, it can’t withstand the loads. As a result, the battery voltage drops to a risky extent. In some cases, the battery voltage can drop to 2 volts. In this case, the engine will not start because the starter motor won’t have enough power to turn the engine on.

Faulty Connections

The connections between the battery and the electrical components in your vehicle should be clean and tight. If the connections are loose or terminals are corroded, it can cause the battery voltage to drop while turning the ignition on.

Bad Alternator

An alternator recharges the battery so that it can restore its power to use when necessary. If the alternator isn’t functioning correctly, it won’t be able to charge the battery fully. As a result, the battery voltage won’t be enough for the ignition.

Symptoms of Battery Voltage Drops When Ignition Is Turned On

The following symptoms will help you identify a voltage drop while turning the ignition on.

The Engine Will Crank Slowly or Won’t Crank at All

If the battery voltage drops by 2-3 volts, the cranking will be sluggish. You will notice the engine is struggling to turn on. If the battery health is too poor, the engine might not crank at all. 

Lights Will Be Dimmed

As soon as you turn the key from the ‘Lock’ position to the ‘On’ position, the electronics in the vehicle can be activated. For example, you may have turned the headlights on. 

If the lights get dimmed while turning the ignition to the ‘Start’ position, it indicates the battery voltage has dropped. Other lights on the inside or outside of the vehicle will also get dimmed.

Electronics Will Flicker

Your vehicle might have a lot of electronic equipment, such as instrument lights, displays, etc. If the battery voltage drops while turning the ignition, these accessories will start flickering. The duration of the flickering will indicate the intensity of the problem.

If these accessories flicker for a short period, the battery voltage may drop slightly. But if the accessories get reset, it indicates the battery voltage is dropping too much.

Diagnosing Battery Voltage Drops in Your Vehicle

You can perform the following tests to diagnose if the battery voltage is dropping.

Test 1: Voltage Measurement

Take a multimeter and measure the voltage between the battery terminals before turning the ignition on. A healthy battery should give an output voltage of about 12.6 volts. If your battery voltage is lower than 12 volts, the battery health might not be good. It is the probable cause behind the problem.

Test 2: Load Testing

You will need assistance with this. Turn the key to the ON position, but don’t start the engine. Then, turn the headlights of the vehicle on. Also, keep the multimeter connected to the battery terminals while starting the engine. Ask your assistant to observe the headlights and the reading on the multimeter.

Turn the key to the START position to crank the engine. If the headlights flicker and the voltage output drops below 9.6 volts, the battery has lost its ideal load capacity.

For better results, you should get the battery checked by an experienced technician.

Test 3: Electrical System Test

You should visually examine the electrical connections between the battery and the starter motor, alternator, etc. All connections should be tight. Also, check if there is any corrosion on the terminals.

Also, get the alternator tested by an expert to ensure it is working correctly.

Battery Voltage Drops When Ignition Turned On: How to Fix It?

It depends on what you have found in the diagnosis. I am providing all possible solutions below.

1. Fixing Connections

• Clean the battery terminals by scrubbing them with a wire brush. It will remove any rust or corrosion from the terminals.
• Tighten the connections to reduce voltage drops.

2. Charging Battery

• If the battery voltage is less than normal before turning the ignition, you should recharge the battery.
• To do this, you should turn the electronics off. Then, remove the battery cables. The negative or black cable will go off first, and the positive cable next.
• Connect a car battery charger to the battery terminals and charge the battery until it shows 12.6 volts.
• Disconnect the charger and put the battery cables on. This time, the positive cable will go first.

3. Replacing the Battery or Alternator

• If the battery is too old or the battery health is too poor, you should replace the battery. It will cost about $150-$250, depending on the brand and quality.
• Also, you should get the alternator fixed or replaced by a mechanic if it doesn’t function properly.

4. Reducing Accessory Load

• You should consider removing unnecessary accessories from the vehicle that may hinder the ignition process. At least remove them until you fix the problem.

FAQs

The answers to the following questions may help you understand the problem better. Check them out.

Final Words

A slight drop in the battery voltage when starting the engine is negligible. But when the voltage drop is significant, the engine will have a hard time starting. You need to know the reasons why the battery voltage drops when the ignition is turned on.

I explained the reasons and mentioned distinct symptoms. They will help you detect the problem at an early stage. Then, you can run the diagnosis and find out the main reason behind the problem. 

I also provided the necessary solutions so that you can get rid of the problem. Try these solutions to make your engine start smoothly without any voltage drops.