The main reasons behind a car battery has voltage but no amps are a dying battery, bad contact between rectifier and load, loose connection, malfunctioning battery cell, and high resistance.
You’d have to replace the battery to solve this problem in most cases. However, you can get away with cleaning the terminals of the battery if they’re corroded.
Keep reading this article to find out more about these issues in detail and how can you solve them. We’ll also discuss how to check amperage on a car battery using a multimeter. Let’s dive in!
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Car Battery Has Voltage But No Amps [5 Easy Fixes]
Voltage and amps are two different things. While voltage is a measure of the pressure that allows the electrons to flow in a circuit, amperage measures the volume of electrons.
It’s common to see your car getting voltage but no amps and there could be many reasons behind it. Here are the most common ones:
Note: You can also read how to fix the hooked battery up backward now car won’t start.
1. Dying Battery
Batteries aren’t meant to last forever. Like all things, they also have a life span and they’ll go bad when the time comes.
If your battery has voltage but no amps, it’s a sign that it’s reaching the end of its intended use. The battery dies due to sulfation of the plates inside or the acid or both.
You can confirm if your battery is dying by performing a load test on it. You can take it to any auto repair shop and most of them will do the load test on your battery for free.
You can also perform a conductance test that’ll tell you about the condition of your battery in a few seconds.
A dying battery can start your car but it no longer meets the minimum requirements for your vehicle and it can fail at any time, especially, when it’s exposed to high temperatures.
Though it may not seem immediately necessary, it’s recommended to replace the battery as soon as you can.
2. Bad Contact Between Rectifier And Load
Another common reason behind a car battery having volts but no amps are bad contact somewhere between the rectifier and the load of the battery.
You need to between the load and the anode bar to know if this is the case. If you see a drop in voltage when testing it, you can confirm that there’s a bad connection.
If there’s a bad connection between the anode rectifier and the load, you have to find the area of the bad connection and fix it. Doing so can restore your battery to a good state.
3. Loose Connection
If you have a battery charged but no cranking power, another reason behind it could be a loose connection between the battery and the battery terminals. The terminals can also get corroded with time and result in a bad connection.
To check if the battery has a good connection with the terminals, you can perform a quick load test with a multimeter.
Connect the red lead of the multimeter to the battery post and the black one to the terminal. As you start the car, the voltage reading shouldn’t drop by more than 0.5V.
If the terminals of the battery are corroded, you need to clean them. Follow these steps to clean the terminals of a battery:
- Attach a memory saver or a 9V battery to the battery cables so that the computer memory and important settings of the car are preserved.
- Remove the battery cables.
- Take one tablespoon of baking soda, mix it with one cup of warm water, and put the solution in a bowl.
- Apply the baking soda solution to the battery terminals and battery posts using a soft bristle brush.
- Use a battery post cleaning tool to clean the dirt from the battery posts and terminals.
- Use a small wired brush to clean the side terminals of the battery.
- Take a dry rag and wipe off the cleaning solution after removing the corrosion from the battery terminals and posts.
- Reconnect the terminals to the battery and apply a small amount of grease or petroleum jelly to protect the terminals from getting corroded again.
4. Malfunctioning Battery Cell
If you’re still wondering why I have voltage but no amps, it could be due to a bad cell in the battery. If you’re getting a maximum voltage of 12.4V from the multimeter before starting the car, it means your car isn’t fully charged and that could be the result of a malfunctioning cell.
Start by checking the level of water if you can take off the caps of your car battery. There are six cells in the battery and the water level should be above the cells at all times. Otherwise, the exposed cells will begin to sulfate and cause issues. Add some distilled water to the cells if the water level is low.
You can know for sure if you have a bad battery cell by performing a hydrometer test on the car. The hydrometer measures the gravity inside the battery. If the reading on it is more than 1.275 on any of the cells, that means the battery is going bad.
Check all of the cells as all of them together create the CCA of the battery. If you see a difference of more than 0.5 in any of the cells while performing the hydrometer test, it also means that there’s a faulty battery cell.
If the battery cells aren’t clean, you can start by applying a battery conditioner to clean them. It’ll expand the life of the battery by a few months before it eventually goes out. It only works if the sulfation is minor.
Remember that batteries have strong acids inside them and make sure you’re wearing protective equipment before taking a look or working inside them. While using a conditioner will expand the battery life for a while, the only permanent solution is to replace the battery.
5. High Resistance
When the battery is used for a long period, there can be high resistance in it that causes the voltage to drop when you start the car. This drop in the voltage is the result of a higher load due to the energy needed to start the car or power electrical lighting and so on.
When the battery has high resistance, it’s an indicator that it’s about to die soon. The ideal solution here is to replace the battery so that you no longer run into any issues with your battery in the foreseeable future.
How To Test Car Battery Amps With A Multimeter
You can easily check the amperage of a car battery using a multimeter. One necessary step you must take before testing the amperage is to test the voltage in the battery. Here’s everything you need to do to test both the voltage and amperage of a car battery:
i). Turn On The Headlights
When you turn on the headlights in your car, it’ll get rid of the excess charge in the battery and give you an accurate reading. Keep the headlights on for at least 30 seconds before you connect the multimeter to it.
ii). Connect The Multimeter
You need to use the DC volts option in the multimeter to test the voltage of the battery. There’s usually the letter “V” in the multimer which represents DC volts. Using a 20V range is good enough to test a car battery as it’ll show the results between 0V and 20V.
Turn the dial of the multimeter to 20 DC volts. Connect the red line of the multimeter to the positive battery terminal and the black light to the negative battery terminal. That’ll give the reading of the battery voltage.
iii). Measure The Reading
If the reading is above 12.6 volts or more, it means that the battery is fully charged. If it reads less than 12.4 volts, then you need to recharge your battery before moving on to the other steps for the test. Keep these readings in mind to know the state of your battery from the voltage reading:
12.6 Volts or Above – Battery is fully charged.
12.4 – 12.6 Volts – Battery is 75% charged.
12.2 – 12.4 Volts – Battery is 50% charged.
12.0 – 12.2 Volts – Battery is 25% charged.
11.9 Volts or Below – Battery is discharged.
iv). Recharge The Battery
If you’ve sufficient charge in your battery, you can skip this step and move on to the next one. But if you don’t have enough charge, let’s find out how you can recharge your car battery.
You can recharge the battery using a portable charger or take it to a shop and have your battery recharged. You can also drive the car for at least 30 minutes to recharge the battery. Keep in mind that simply turning on the engine and letting it rest will not charge the battery. You’ll have to drive it.
v). Perform A Load Test
This is where you’ll know if you have to replace the battery. You need to do this test with a fully charged battery to get accurate results. Make sure you charge your battery before performing this test.
The voltage in your car battery will drop to a certain extent when you start the car. But keep in mind that it should never drop below 9.6V. If it goes below 9.6V, you’ll have to replace the car battery.
Start the car with the multimeter connected to it. Multimeters have latency and they take a fair amount of time to process voltage into numbers. It only takes a few microseconds for the voltage to drop down in the battery. So, don’t rely on simply looking at the multimeter for the perfect results.
Your multimeter will have a Min/Max button that’ll show both the minimum and maximum values of the car battery voltage. If the reading is below 9.6V, you know that you have a faulty battery and you’ll have to replace it.
vi). Check The Amperage
If there are no issues with the voltage in your battery, you can check the amperage in the battery. All the car batteries come with a predefined CCA (Cold Cranking Amps) reading. If the amperage reading is too low compared to the CCA, it also means that you have a bad car battery.
Can a battery have good voltage but still be bad?
A battery can have over 12.6 volts before starting the car but it can dip down to less than 9V when you start the car. That means a car battery can have good voltage and still be bad.
What voltage is too low for a 12-volt battery?
Anything that is less than 12.6 V means that the battery isn’t fully charged. But if it’s below 11.9V, then the battery is discharged and it needs to be recharged if you want to use it again.
Why is my car battery showing 15 volts?
If your car battery is showing 15 volts, there’s most likely a problem with the alternator. Cleaning or replacing the alternator should solve this issue.
Can you run a car without a battery?
It’s possible to run a car without a battery if the alternator is large enough to provide the electricity needed for the car. But you’ll have a hard time starting the car without a car battery.
How many amps is the car battery?
A car battery normally has a capacity of 48 amp hours. It means that it can deliver 1 amp current for 48 hours or 6 amps current for 8 hours when it’s fully charged.
When your car battery has voltage but no amps, more often than not the only solution is to replace the battery. Diagnosing the main reason behind this issue can be difficult. But hopefully, this guide will help you identify the cause of why your battery is malfunctioning and help you fix it.
Make sure you wear protective gloves and eyewear when you look inside the cell of the battery or do any work on it. Leave a comment below if you have any more questions about a car battery.