How to test if a car battery charger is working

Car Battery Testing & Voltage: It’s important to test your battery and electrical system regularly, not just when it’s starting to show signs of weakness. Proactively testing it (or making sure your mechanic does) twice a year will help reduce your chances of failure. Most retailers offer a simple free five-minute battery test. Use our Find a Retailer for a location near you to get a free battery test.

When fully charged, how many volts should a car battery have? charged automotive batteries should measure at 12.6 volts or above. When the engine is running, this measurement should be 13.7 to 14.7 volts. If you don’t have a multimeter to tell you the voltage of your battery, you can do a test of your electrical system by starting the car and turning on the headlights. If they are dim, that indicates the lights are running off the battery and that little or no charge is being produced by the alternator. If the lights get brighter as you rev the engine, it means the alternator is producing some current, but may not be producing enough at idle to keep the battery properly charged. If the lights have normal brightness and don’t change intensity as the engine is revved, your charging system is probably functioning normally. If you’ve been experiencing problems with your battery system and the headlight test checks out okay, you should check whether the battery is holding a charge, or if something on the vehicle is discharging it.

How do you perform a load test? To pass a load test, the battery must maintain 9.6 volts at 15 seconds when tested at one-half the CCA rating and 70°F (or above). This test must be done with a true load (carbon pile) and not one of the hand-held testers that work off a conductance algorithm. The test must be run with the battery in a high state of charge. Be sure to read and follow all safety and handling instructions on the battery, this website, and your battery tester. If you would like your battery tested, use our Where to buy and Recycle finder for a location near you.

Troubleshooting a 12-volt battery charger is relatively easy. But you'll need a voltmeter to troubleshoot most chargers. Since the charger is responsible for charging your vehicle's battery, you want to make sure that it is working, that there is no resistance in the lead wires, and that the voltage coming out of the charger is what it should be.

Step 1

Set the dial on the voltmeter to "Ohms" and test the voltmeter. Touch the leads of the voltmeter together. The reading should be "0.00," but a variance of .05 is acceptable. "0.00" represents the resistance in the wires. No resistance means that an electrical current can pass through the lead wires the way it should without any resistance and that there is good connectivity (there is no break in the line).

Step 2

Touch the lead wires on the voltmeter to the lead wires on the 12-volt auto battery charger. It does not matter which lead on the voltmeter touches which lead on the battery charger. All that matters is that one lead touches the power lead on the charger, and one lead touches the negative lead on the charger.

Step 3

Check the resistance. The voltmeter will display a reading when the leads are touching the leads on the battery charger. A variance of .05 is acceptable, but the resistance should be "0.00".

Step 4

Set the dial to the highest volt setting on the voltmeter.

Step 5

Turn the battery charger on. Set the charger to charge at a specific voltage.

Step 6

Touch the power lead on the voltmeter to the power lead on the battery charger. Touch the ground lead (the black lead) on the voltmeter to the negative (or ground) lead on the charger. The voltage output on the voltmeter should be the same as the voltage setting on the charger. If it is not, the charger is malfunctioning and must be replaced.

References

• Automotive Tools Manual: Guide to Buying and Using Automotive Tools; Thomson Delmar Learning; 1999

Things You'll Need

• Voltmeter

Writer Bio

I am a Registered Financial Consultant with 6 years experience in the financial services industry. I am trained in the financial planning process, with an emphasis in life insurance and annuity contracts. I have written for Demand Studios since 2009.

When new batteries that you bought a few months ago don’t seem to work, it gets confusing. Have the batteries already gone bad or is there something wrong with the charger, you start wondering. Don’t worry, we got you covered.

How to test a battery charger?

Put a battery in the charger and plug it into an outlet. Attach probes to a multimeter. Touch the negative side of the charger with the black probe and the positive side of the charger with the red probe. If the multimeter displays the volts equal to the capacity of the battery, the charger is fine.

If you are interested to read more about this topic, we have a detailed segment on it. We will be discussing the multimeter and how to check the charger in step-by-step order in the following parts. Stick with me till the end.

Contents show

Check If Your Battery Charger Is Alright

Things You Would Need

Step 1: Remove the Batteries and Power On

Step 2: Prepare the Multimeter

Step 3: Attach the Black Probe to the Negative (-) Contact Point

Step 4: Attach the Red Probe to the Positive (+) Contact Point

Step 5: Check the Reading and Match

How Does Multimeter Work?

FAQs

Conclusion

Check If Your Battery Charger Is Alright

If you work with rechargeable batteries all the time, you may have a battery charger at your home as well. Batteries get old and eventually die. But when a new battery stops working, we start wondering if the battery charger is okay or not.

Nothing much to worry about though. Checking battery chargers is very easy with a multimeter. Just match the reading of the meter with the batteries.

Apart from battery chargers, a multimeter can check amp, voltage, and other electric measurements. It can be used to test circuit breakers and engine ignition coils as well. But for this article, we will focus just on battery chargers.

Things You Would Need

To check if a battery charger is alright or not, you will need some electrical instruments. You would require:

• A battery / a pack of batteries
• A working power outlet
• A battery charger
• A multimeter
• Probe wires

Step 1: Remove the Batteries and Power On

The first step to check a battery charger will be to remove all the batteries from it. Give the charger a quick cleaning and go to a power outlet to plug the charger in. Choose an outlet that is not hard to plug in.

Power on the battery charger and ensure there’s electricity flow in that. You can check that with the multimeter as well or use a tester screwdriver.

Step 2: Prepare the Multimeter

Grab a multimeter. It should give you the volt measurements once you start giving it input. Find the probe wires and plug them into the multimeter to get started. Put the meter on DCV mode.

The probes consist of two colored wires. The hot one or positive one is painted as red and the idle one or negative one is painted as black. These probes touch the electric source and give a reading on delivered volts.

Step 3: Attach the Black Probe to the Negative (-) Contact Point

The black probe test wire resembles a negative point and should be met with the negative contact of the battery charger. If it is a AA battery charger, then the negative side will have a metal prong.

For other kinds of battery chargers, find the minus (-) marked the negative end and attach the test probe to that contact point.

Step 4: Attach the Red Probe to the Positive (+) Contact Point

The black probe test wire denotes the positive point of the multimeter and must be connected with the positive contact of the battery charger. For AA battery chargers, it has to be on the opposite side of the metal prong.

While checking chargers other than AA type, find the plus (+) marked the positive end and connect the test probe to its contact point.

Step 5: Check the Reading and Match

When the multimeter probes are connected to the contact points of the charger, check the display of the meter. It should have a reading of negative or positive charge in volts.

If the reading of volts from the multimeter matches the volts of the batteries that are supposed to be charged by that particular charger, it’s fine. Otherwise, there are some problems with the battery charger and you should fix or replace it.

For example, AAA, AA batteries have a capacity of 1.5 volts. So, a charger that is built for charging these batteries should output 1.5 volts and a multimeter will read that. If the output from the battery charger is lower than 1.5 volts, it has issues.

Here are some of our recommended battery chargers that you can check out:

How Does Multimeter Work?

A multimeter is one of the most widely used electrical tools. Almost every electrician on earth owns a multimeter. It is called a multimeter because it can give readings of many electrical properties. It’s like an all-in-one tool.

It usually has two probes or needles. The probes are color-coated. Black means negative or idle end, Red means positive or hot end. Digital multimeter also features a digital display, while analog meter has a pointer that swings between positives and negatives.

It can measure grounding, the current, voltage as well as resistance. It can be used to check circuits, batteries, motors, home wiring, power supply, and many more electrical commodities.

FAQs

Question: How do I know if the battery charger is broken?

Answer: You can’t directly identify if your charger has gone bad or not by looking at it. You need to run a test on it using a multimeter to be sure. 

Question: How to check a battery charger amp output?

Answer: Usually, this information is written on the charger body, packaging, or manual it comes with. But you can always check such information using a multimeter.

Question: How do I know if my battery charger is working?

Answer: If the charger is recharging batteries fine, there is nothing to worry about. But if it isn’t then change the batteries first. If that fixes the issue then your charger is fine.

Conclusion

With that, we have reached the end. We hope your battery chargers are okay or you now understand how to test battery charger. If you still can’t figure out how to check your charger, then take it to a technician, he can help you with that.

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