If your black and decker 20 volt battery charger not working, the most common cause is poor contact between the battery terminals and the charger pins, which can usually be resolved by cleaning the contact points.
Reasons your 20 volt battery charger fails
Charging issues usually stem from a lack of electrical flow. Dirt, dust, or light oxidation on the metal contact points creates a barrier that prevents the charger from sensing the battery. Sometimes, the issue isn’t the charger at all, but a faulty power source or a tripped circuit breaker in your home. If the charger is plugged into a switched outlet, ensure the wall switch is in the on position.
Safety: Inside a mains-powered machine, the parts behind the outer cover can hold a dangerous electrical charge even after it has been unplugged — that’s why they sit behind a cover. Opening the housing, or testing or replacing anything behind it, is a job for a qualified technician, never a home repair.
Clean the contact points
This fix is for users who see no lights on the charger when the battery is inserted. Take a soft, dry cloth and gently wipe the metal contacts inside the battery port and on the battery itself. If you see dark spots or debris, use a dry cotton swab to clear them. Don’t use liquids, sprays, or metal objects like screwdrivers to clean these points, as you could damage the delicate pins or cause a short circuit. If the lights remain off after cleaning, the internal sensors may be failing to detect the charge. This varies by model — check the label on your charger to see the expected light patterns.
Reset the power connection
If your charger has power but refuses to charge the battery, perform a hard power reset. Unplug the charger from the wall outlet and wait at least 60 seconds to allow the internal capacitors to discharge fully. While you wait, remove the battery from the unit. Plug the charger back into a different wall outlet that you know works with other devices, then slide the battery back into the slot until it clicks. If the status light stays solid red or off, the charger might be unable to complete the handshake required to start the charging cycle. This is a common trade-off with older, heavily used units.
Test with a different battery
If you own more than one battery, swap them to isolate the problem. If a second battery charges normally, the first battery is likely the issue rather than the charger. If neither battery works, the charger has likely reached the end of its service life or has an internal fault. You should never attempt to open the charger housing to fix internal components, as a capacitor can hold a lethal charge even when unplugged. If your troubleshooting steps don’t resolve the issue, contact the manufacturer or a certified service center for a replacement unit.
What not to do
- Don’t use sandpaper or metal files on the charger pins, as this removes the protective coating and causes permanent corrosion.
- Don’t force the battery into the charger if the plastic housing looks melted or warped, as this indicates a severe thermal failure.
- Don’t spray cleaning chemicals into the battery port, as liquid residues inside the housing will cause electrical shorts.
How to stop it happening again
Keep your batteries in a cool, dry place to prevent moisture buildup on the terminals. This keeps the electrical path clear and extends the life of your equipment.
| If you’re doing this | Do this instead | Why |
|---|---|---|
| Leaving batteries in the cold | Store at room temperature | Cold slows chemical reactions |
| Storing in a damp shed | Use a sealed plastic bin | Humidity causes terminal rust |
| Ignoring dust on contacts | Wipe with a dry cloth | Dust blocks the charge signal |
Frequently asked questions
Can I fix a flashing red light on my charger?
Yes, a flashing light often indicates the battery is too hot or too cold to charge. Move the battery to a room-temperature area for 30 minutes, then try again. If it continues to flash after cooling, the battery pack may have a dead cell.
Why is my charger getting very hot?
It’s normal for the charger to feel warm, but it shouldn’t be hot to the touch. If the unit smells like burning plastic or is too hot to hold, unplug it immediately. This indicates an internal component failure that you can’t safely repair.
How long does a 20 volt battery take to charge?
It typically takes between 3 to 5 hours for a full charge, depending on the battery’s amp-hour rating. If your battery takes significantly longer, the charger may be failing to provide the correct voltage, or the battery has lost its ability to hold a full charge.
Is it safe to leave the battery on the charger?
Modern chargers are designed to stop charging automatically once the battery is full, so it’s generally safe to leave the battery on the charger.
What happens if I use a different brand’s charger?
You should never use a charger from a different brand, as this can cause a fire or damage the battery. Chargers are specifically calibrated to the voltage and safety protocols of the original manufacturer’s battery packs, and mixing brands voids your warranty.
Final Thoughts
If your device still won’t charge after cleaning the connections, the internal circuitry might be damaged. Don’t worry, as it’s often cheaper to replace the unit than to pay for professional repairs. Check your local hardware store’s return policy, or look for a compatible replacement online to get back to work.
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Dorothy Addeo is a senior product reviewer at Safefins.com with years of experience testing kitchen, furniture, backpacks, and everyday lifestyle products. She focuses on comfort, durability, usability, and long-term value through hands-on research and real-world testing. Her goal is to help readers find reliable products with honest, easy-to-understand recommendations they can trust.