dewalt 20v battery charger not working

Introduction

Your DeWalt 20V Max drill is one of your most reliable tools until it stops working because the battery won’t charge. This is a common issue faced by DIYers and professionals alike. In many cases, the problem isn’t the battery being "dead," but rather needing a simple reset or minor maintenance. This guide walks you through how to fix a DeWalt drill battery that’s not charging and potentially save yourself the cost of a new one.

Common Causes

If your DeWalt drill battery is not charging, it’s often due to one of the following:

Deep Discharge: The battery has been drained below the voltage threshold and the charger can no longer detect it.
Dirty or Corroded Terminals: Dirt, rust, or corrosion on the metal contacts can block current flow between the battery and the charger.
Defective Charger or Power Source: Sometimes, the charger itself is faulty or not plugged into a stable power outlet.
Battery Overheating or Age: Older batteries may lose the ability to hold charge, or overheat due to internal degradation.
Infrequent Use: Leaving batteries unused for months can lead to voltage loss and cause the battery to become unresponsive.

Step-by-Step Fix

Let’s walk through how to reset your DeWalt battery and bring it back to life.

1. Safety Tip First

Before handling any battery or charger, always take proper safety precautions:

Unplug the charger from the outlet.
Wear insulated gloves and safety glasses.
Do not attempt repairs if the battery is swollen or leaking.

2. Step 1 – Check the Charger and Power Source

Before blaming the battery, make sure the charger is working:

Insert the charger into a different outlet that is working. If a different battery is accessible, charge it up. If the other battery charges, the charger should be working properly. If every battery you put in doesn’t light up, there could be an issue with your charger.

3. Step 2 – Gently Clean the Battery Terminals

Because dirt and oxidation sometimes collect there, make sure the cleaning liquid has no moisture: cotton swab with a drop of rubbing alcohol or contact cleaner. Gently massage both the battery and charger terminals, making sure they become clean and without grime. It’s good to leave the switch off and the battery out for about a minute before use.

4. Step 3 – Jumpstart a Deeply Discharged Battery

When the lithium-ion battery drops below a certain voltage, it cannot be detected by the charger.

To boost the battery:

Place a similar fully charged 20V battery nearby (the bad battery shouldn’t be connected yet).
Link the positive (+) terminal of the working battery to the positive (+) terminal of the dead battery using a short wire.
Perform the same work on the negative (–) terminals.
Keep the connection for between 30 and 60 seconds.

It delivers a slight amount of current to the battery, but it’s enough to bring that battery back to life. Following jumpstart, straight away go ahead and reconnect the battery to the charger.

⚠️ Caution: Do this step only if you are certain you can handle electronics. If wiring is not done correctly, it can be harmful.

5. Step 4 – Re-Charge in the Charger

Once the battery has been reset:

Place it in the charger.
As soon as you charge your battery, the light will turn red or start flashing.
After 15–30 minutes with the battery on the charger, check if it runs well in your drill.

If you can use the drill without worrying about its battery, the problem is solved!

How to Use a Multimeter to Check the Battery

If you’d like to test the battery, use your multimeter:

Sustain the red probe on the metal body of the positive and the black one on the body of the negative.
If you check your battery and it reads around 18V to 20V, you know it’s working well.
It’s possible the charger will not be able to find the battery if it runs on just 12V.

When the Battery Still Won’t Revive

From time to time, despite your best efforts, the battery simply won’t revive.

If your battery heats rapidly within a few minutes of charging, that’s a clear sign it needs replacing.
A reset won’t solve the issue since the battery won’t charge afterward.
If the battery has been used for 3–5 years or more, or you notice visible signs of damage or swelling, it’s time to replace it.

You might pay between $60 and $90 for a new DeWalt battery, but this will be less costly than always dealing with stress or damage to your equipment.

Some Ways to Avoid Issues

Store Properly: Keep batteries in a dry and cool location. Do not place your items where they will experience high or low temperatures.
Avoid Long Inactivity: Long periods of inactivity for a battery may result in deep discharge.
It’s Right to Charge Early: You don’t have to let your lithium-ion battery get very low before putting it on the charger. Actually, it is not good to charge the battery above 30–50%.
Regular Maintenance: Don’t forget to clean your wires every so often to avoid corrosion.

Common Myths About Lithium-Ion Batteries

Myth 1: You need to remove all the power from the battery before it gets charged.
False – These batteries do better when you only charge them halfway.
Myth 2: If your battery is dead, you can’t use it.
False – This guide reveals that many "dead" batteries may still be able to work.
Myth 3: It’s okay to keep batteries in the fridge.
False – Lithium-ion batteries do not perform well in cold weather.

Conclusion

You can easily fix a DeWalt 20V Max drill battery that doesn’t charge if you know what to do. If you clean the terminals, examine the charger, and use safe jumpstarting methods, you don’t have to buy a new battery.

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