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How to Tell if a Dewalt Battery is Bad

How to Tell if a Dewalt Battery is Bad

Power tools are an important aspect of hobby wood workers and professional building contractors alike. The convenience of being able to carry around a tool with you to take care of problems at a moment’s notice, while not having to worry about tripping over chords cannot be underestimated. Obviously for a power tool to be a good and effective one, it needs to have batteries that last a long time.

One well known power tool company is Dewalt. Their batteries can last three years before needing to be replaced. However, there are times when you may have just recharged it and the battery dies out right in the middle of a job. If this keeps happening with the same tool with the same battery, it is important to figure out why. Let’s take a look at some of the signs that can tell you whether your Dewalt battery is bad or if the charger is bad.

Is the Battery Bad or is the Charger Bad?

There are two ways you can tell if a Dewalt battery is bad and needs to be replaced. The first way is by using a charger. The second way is by using an altimeter. Because the charger method is the simplest way, that is what we will focus on in this article, but you can read more about the altimeter method here.

Testing With a Charger

For this method you will need the battery that you suspect is faulty, another battery that you know is good, and a charger. It is important to have both a good battery and faulty battery as you will be using them as a comparison to ascertain whether the battery is bad or the charger needs fixed. Then take the following steps:

Plug in the Charger

Do not put the battery into the charger right away as the charger needs a few seconds before it is ready to be used. There is an indicator light on the charger which will turn red when it can start charging.

Plug in the Good Battery

After the charger has been plugged in for several seconds, the light should turn red. At this point, take the good battery and put it into the charger. You should see the following (or some combination) happen:

  1. A blinking red light. The blinking red light is an indicator that the battery is charging normally.
  2. A blinking red light which turns yellow. The yellow light is an indication of one of two things-either the battery is too hot, or it is too cold. If the battery is too hot it means it was just in use or was used for a long time. If it is too cold, it means that it hasn’t been used for a while or it is cold out.

Either way, it doesn’t necessarily mean that there is anything wrong with the battery. Wait a few minutes and the yellow light will go off and charging will resume.

  • The red light stops blinking. This is an indication that the battery is completely charged.
  • The lights shut off completely. If the light shuts off, then it could be an indication that the battery OR the charger is faulty. 

Repeat the Process with the Faulty Battery

Next remove the good battery, plug in the faulty battery, and keep an eye on the indicator lights. If you charged the good battery and the indicator light showed only the first 3 options, then it is likely that the battery is, indeed, bad and needs to be replaced.

However, if you charged both batteries, and with both the lights shut off completely, then it is more likely that the Dewalt charger is bad. You will need to take it to a service center for assessment.


Power tools provide a lot of convenience, especially for this in the building industry. However, the downside is that they require good, long lasting batteries to be effective. Dewalt is well known for both its power tools and for its battery longevity. However, there are times when you will have just charged the battery and your tool dies out in the middle of a job.

If this happens it is important to know if the fault lies with the battery or with the charger. To test this charge both the battery in question and another battery that you know isn’t faulty. If the indicator light shuts off completely when charging both, then the charger is likely the problem. If the light only shuts off with the battery you’re not sure about, then the battery is likely the problem and needs to be replaced.