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How To Fix A Dead Battery That Won't Charge?
April 10, 2025 leedevin

How To Fix A Dead Battery That Won't Charge?

Why Is My Lithium Battery Not Charging?

There are several possible reasons why your lithium battery won’t charge. Most of them are related to safety features, battery condition, or charger compatibility.

✅ Common Causes & Fixes:

 
Cause Explanation What You Can Do
Over-discharge protection If the battery voltage drops too low, the charger may not recognize it. Try a jump-start or use a smart charger.
Temperature issues Batteries won't charge if they’re too hot or too cold. Let the battery rest at room temperature (15–25°C).
Charger malfunction or mismatch The charger may be faulty or not compatible. Try another charger or check voltage compatibility.
Dirty or damaged contacts Dirt or corrosion can block the connection. Clean the battery terminals gently.
Battery age or internal damage Old or damaged cells may no longer accept a charge. Consider replacing the battery.
Built-in battery protection triggered Some tools/batteries have BMS that cuts off for safety. Reset or leave idle, then retry after a few minutes.

How to Reset a Power Tool Battery That Won’t Charge

⚠️ Note: These steps are for lithium-ion batteries. Always follow safety precautions and wear protection if needed.

Option 1: Remove and Reinsert the Battery

Sometimes it's a connection issue:

  1. Remove the battery from the charger.

  2. Wait 10–30 seconds.

  3. Reinsert it firmly into the charger.

  4. If your charger has indicator lights, watch for any changes (e.g., from blinking to solid light).

    Option 2: Jump-Start the Battery (Advanced)

    This is useful if your battery is over-discharged and the charger won’t recognize it:

    🔧 You’ll Need:

    • A second, fully charged battery (same voltage)

    • Two wires or jumper leads

    💡 Steps:

    1. Connect the positive terminal (+) of the charged battery to the positive of the dead battery.

    2. Connect the negative terminal (–) to the negative.

    3. Hold the connection for 15–60 seconds — no longer!

    4. Disconnect and place the “dead” battery back in the charger.

    5. If successful, it should now begin charging.

    ⚠️ Do this only if you're familiar with basic electronics. Incorrect handling can be dangerous.

Option 3: Use a Smart Charger

Some chargers have a refresh or recovery mode designed to revive over-discharged batteries. Check if your charger supports this.

Option 4: Let It Cool Down

If the battery is too hot or too cold, it might refuse to charge:

    • Let it rest in a room-temperature environment (15–25°C / 60–77°F) for 30–60 minutes.

    • Try charging again.

When to Replace the Battery

If:

    • The battery won’t hold a charge

    • It shows no response after jump-start

    • The case is swollen or damaged

👉 It’s time for a replacement.

Mellif Battery that Compatible With Dewalt：https://mellif-tools.com/products/mellif-charger-kit-20v-4-0ah-lithium-ion-battery-fast-charging-charger-compatible-with-mellif-20v-tools

Mellif Battery that Compatible With Makita：https://mellif-tools.com/products/mellif-18v-4-0ah-battery-and-charger-replacement-for-makita-battery

 

Filed in: dewalt
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