craftsman drill charger light is on but my battery isn't charging. what do i do?

Diagnosis

This issue typically occurs when the charger's internal logic detects a connection (triggering the light), but the actual current flow to the lithium-ion cells is interrupted. In the CRAFTSMAN V20 system, this is most often caused by "surface oxidation" or debris on the copper contact points. Even a microscopic layer of dust or oil from your hands can create enough resistance to prevent the charging circuit from initiating, even while the LED indicates the charger is powered on. Another common cause is a "deep discharge" state. If the V20 battery has dropped below a specific voltage threshold (typically around 12V-14V for a 20V pack), the charger's safety protocol prevents it from sending a high-current charge to avoid overheating or cell rupture. In this state, the charger may show a light, but it won't actually push power into the cells because it perceives the battery as defective or unstable. You can confirm this by checking if the battery feels unusually cold or if the drill fails to trigger even for a split second when a fresh battery is swapped in.

How to Fix It

Follow these precise steps to clear the connection and reset the charging cycle:

1. Unplug the charger from the AC wall outlet completely to discharge the internal capacitors.
2. Remove the battery pack from the charger. Use a flashlight to inspect the gold-plated contact pins on the charger and the corresponding terminals on the battery. Look for any black carbon buildup or green corrosion.
3. Take a cotton swab dipped in 90% isopropyl alcohol and firmly scrub the terminals on the battery. Then, gently clean the spring-loaded pins on the charger. Do not use metal scrapers or sandpaper, as this will strip the gold plating and lead to permanent connectivity failure.
4. Allow the alcohol to evaporate for 60 seconds.
5. Inspect the battery casing for any signs of swelling or "bloating." If the plastic shell is bowing outward, the battery is chemically compromised and must be recycled.
6. Plug the charger back into a known-working outlet (avoid using a power strip for this test to ensure maximum current).
7. Slide the battery into the charger with a firm, decisive motion. Ensure the battery clicks fully into place; if there is any gap between the battery base and the charger housing, the pins will not make full contact.

If That Didn't Work

• The "Jumpstart" Method: If the battery is deep-discharged, try inserting and removing the battery from the charger rapidly 5 to 10 times. This can sometimes "wake up" the battery management system (BMS) by sending short bursts of current that bring the voltage back up to a level where the charger recognizes it as a valid battery.
• Temperature Reset: Lithium batteries have thermal cut-offs. If the battery is too hot (from heavy use) or too cold (stored in a garage during winter), it will refuse to charge. Place the battery in a room-temperature environment (65°F to 75°F) for at least four hours before attempting to charge again.
• Cross-Testing Hardware: Borrow a known-working V20 battery from another tool or use a different V20 charger. If the second battery charges on your charger, your battery pack has a dead cell. If your battery charges on a different charger, the internal transformer or capacitors in your original charger have failed.
• Contact Tension Adjustment: Use a small needle to gently ensure the spring-loaded pins on the charger are actually springing back up. If a pin is stuck in the "down" position, it won't make contact with the battery terminal.

Heads Up

• Never store your V20 batteries completely drained; always keep them at least 25% charged to prevent the deep-discharge state described above.
• Avoid charging batteries in environments below freezing or above 100°F, as this permanently degrades the cell capacity.
• Keep the charger vents clear of sawdust and debris; overheating the charger can cause the internal thermal fuse to blow, rendering the unit useless.
• Only use official CRAFTSMAN V20 chargers; third-party "universal" chargers often lack the specific communication protocol required by the V20 BMS, which can lead to overcharging or fire hazards.