UniEnergy Technologies Battery ยป How To Test A Battery Charger? (2 Effective Methods)

How To Test A Battery Charger? (2 Effective Methods)

A battery charger restores energy to batteries by running current through them. So, once your rechargeable batteries die, there’s no need to dispose of them. Just put them on the battery charger and charge them!

But, sometimes, even this device fails you. It would charge the batteries partially or not at all. This is especially true when you haven’t picked a good brand like Dewalt.

So, should you throw away a bad battery charger and buy a new one? Certainly not!

Although a good battery charger doesn’t cost much, it’s always a better idea to test and confirm whether it’s defective. There can be some other underlying reason too.

Well, in today’s post, we will explain how to test a battery charger using 2 different methods. We’ll also talk about the causes and solutions. Let’s dive in!

Why Do Battery Chargers Go Bad?

Battery chargers going bad means they no longer function efficiently. You’ll find it difficult to charge the batteries fully, and sometimes, they won’t charge at all. This can occur for numerous reasons, including:

  • Manufacturer defect- although this is rare, battery chargers can be non-functional from the first day. If this happens, know that the piece is faulty and must be exchanged.
  • Rust and moisture- the metal terminals of the battery charger are the keys to energy transfer. If they’re damaged or rusted due to moisture, the charger won’t work.
  • Input power supply- poor electric input can reduce the performance efficiency of a battery charger. So, always make sure the electricity isn’t fluctuating and is compatible with the requirement of the charger. Avoid using power strips too.
  • Temperature- battery chargers often come with built-in temperature sensors.  When the temperature rises above the tolerance level, the charger automatically cuts the supply until things cool down a bit.
  • Safety timer- most battery chargers must get manually separated from the electric supply to stop charging. However, modern versions come with safety timers. They automatically stop charging when the batteries are full.

A problem within the sensors or timers can cause premature disruption in the energy supply. Hence, resulting in poor charge performance.

How Can You Tell If a Battery Charger is Good?

How Can You Tell If a Battery Charger is Good

The simplest way to tell if a battery charger is good is to plug the device into an electric outlet. Insert some batteries and turn on the battery charger. If it starts to charge, then you’re good to go!

However, you still won’t know whether the batteries are receiving the required charge or not. To find this, you must test the battery charger and check its output.

Typically, a good battery charger should generate an output between 12 volts and to 14-volts. This range allows you to charge both small and large device batteries. That said, it’s best to consult the battery charger manual and ensure it’s providing the recommended supply.

How to Test Battery Charger?

Test Battery Charger

Testing a battery charger isn’t a difficult task. All you need for this procedure is a battery charger and a device to test it.

Below, we have discussed how to test a battery charger using 2-different devices; a multimeter and a load tester. It’s great if you have both to test the charger, but even one would be sufficient. Let’s see how!

Method 1: Using a Multimeter

A multimeter (also called a voltmeter) is a measuring device that is easily available in all hardware and electrical shops. As the name suggests, it is capable of measuring several electrical components. These include current, voltage, and resistance.

Here’s how you can use it to check your battery charger:

  • Unplug the battery charger from any electric wall outlet and remove the batteries.
  • Now, connect the battery charger back to the electric outlet. If there’s an on/off button, use it to ensure electricity is running through the device.
  • Prepare the multimeter by attaching the probes to the right terminals. There are typically two detachable probes; black (negative) and red (positive). The black probe is attached to the COM port, whereas the red probe is attached to the V port.
  • Use the huge dial on the multimeter to enter the DC mode, and stop the dial on the next highest voltage that you’ll be measuring. For example, if you’re going to measure a 1.5-volts AA battery, choose 2 DCV.
  • Now, hold the test probes and carefully touch the battery terminals. The black lead should come in contact with the metallic part of the negative side and vice versa.
  • Check the numbers displayed on the meter screen. The shown voltage should be equal, if not more, than the batteries you want to charge. However, if there’s a negative reading or none at all, know that you have mixed up the probes.

Method 2: Using a Load Tester

A load tester is a hand-held device that applies a calibrated load to the battery charger and checks whether it can hold the specific charge. The more current output, the better your battery charger is. Follow these steps for the test procedure:

  • Remove the batteries from the charger and connect them to a power supply.
  • Check the probes of the load tester and attach them to the battery charger accordingly. Remember, the negative probe will be linked to the negative terminal and vice versa.
  • Switch on the load tester and input the values you want to test.
  • Press the Test button.
  • Read the measurements on the screen. You can also print the readings in advanced load tester models.

How to Troubleshoot a Battery Charger?

How to Troubleshoot a Battery Charger

It’s unwise to consider that the problem is with the battery charger when it stops working. The problem can be something else too. And so, you should follow the proper troubleshooting method.

1. Power Supply

First, check out the power cord and supply since that’s where the electricity is coming from. It’s possible for the supply to fluctuate or be insufficient. So, plug another device into the same outlet.

If it turns on, the problem is not in the electric supply. You can further verify this by plugging the battery charger into another outlet.

2. Batteries

Typically, rechargeable batteries have a lifespan of 2 to 7 years. But they can easily become defective when not used over an extended period. So, the next step is to test the batteries.

Insert the batteries in another charger to ensure the problem is not within them. Or, if you don’t have another charger, use a different set of batteries on the same charger.

3. Battery Charger

If the problem is not in the circuitry or batteries, it’s obvious the battery charger is faulty. This doesn’t mean you should just replace it.

A battery charger can be repaired if there’s a disconnected wire or blown fuse. In some cases, an expert can also help replace the rusted metallic parts to make the charger functional again.

However, if nothing works, the solution is a replacement. Our suggestion would be to choose a good battery charger that:

  • Is compatible with the battery type and size
  • Offers the required voltage
  • Has a long cord for easy charging
  • Has a safety timer and light indicators
  • Has a warranty

Some durable battery charger brands include DEWALT, Schumacher, Noco, and Optima.


1. What is the Lifespan of a Battery Charger?

The average lifespan of a battery charger is 1.5 to 3.5-years. This is about 300 to 1000 charge cycles. However, it really depends on the product quality, usage, and care.

2. How to Test a Battery Charger without Battery?

Usually, a battery charger is tested without batteries. You can use a multimeter or load tester to perform the tests.

3. How to Test a Car Battery Charger?

The above-mentioned methods to test a battery charger are general. You can use them to check all types, including car battery chargers.

4. How to Test DEWALT Battery Charger?

The easiest way to test a DEWALT battery charger is to look at the indicator lights. There should be a red blinking light on the charge mode and a yellow blinking light on the trickle charging mode. But, if there’s none, know that your Dewalt battery charger is faulty or damaged.

5. What voltage should a battery charger put out?

Functional battery chargers should put out at least 12 volts to restore decent amounts of energy in batteries. But, if you wish to charge batteries for large devices, the voltage output should be up to 14 volts.


All in all, you can test a battery charger by using a multimeter and load tester. For both devices, the basic test methods are the same:

  1. Connect the battery charger to the power supply without the batteries.
  2. Attach the probes of the testing device to the correct battery terminals. The positive probe will go with the positive terminal and vice versa.
  3. Check the reading to ensure it is equivalent or more to the batteries you want to charge.

We usually recommend people with zero experience in electrical processes seek professional technician help. But testing a battery charger is so easy and simple that anyone can do it!

If you try out any of these methods, do let us know about your experience in the comments below!

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