Quick answer
- On the Kobalt KRC 40-06 40V Max charger, a blinking red light means a charging fault and a solid red light means the battery is over temperature. Blinking green means charging, and solid green means fully charged.
- Solid red: let the pack cool in the charger, and charging resumes when it is back in range.
- Blinking red: remove the battery for 1 minute and reinsert it. If it still blinks red, unplug the charger for 1 minute, then plug it in and reinsert the battery. A battery that still blinks red after that is defective, according to the manual.
- These meanings are for the KRC 40-06. Check the manual for any other Kobalt charger before you trust the colors.
Symptoms
When your Kobalt 40V battery won't charge, you may see:
- The charger showing blinking red (charging fault) or solid red (over temperature).
- The battery not powering your tool, even when fully inserted.
- The charger showing no light at all, which points to the outlet or the charger itself.
Quick checks
- Temperature: the KRC 40-06 manual says charging begins once the pack is between 37°F and 117°F (3°C to 47°C). If the air is below 45°F or above 104°F, move the charger and battery to a room-temperature spot.
- Charger: use a Kobalt 40V Max charger. The KRC 40-06 manual lists the 40V packs it charges, including the KB 440-06.
- Terminals: remove the battery and look for dirt or corrosion on the contacts. Clean them gently with a dry cloth.
- Second battery: try another compatible Kobalt 40V pack in the same charger. If it charges, the first battery is the problem.
- Outlet: plug the charger into a different outlet to rule out the power source.
Step-by-step fix
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Read the light. Blinking green is charging and solid green is done. Solid red is over temperature, and blinking red is a charging fault (Kobalt KRC 40-06 manual).
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If it is solid red, leave the battery in the charger and let it cool. Charging resumes when the pack is back in range.
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If it is blinking red, run the manual's reset: remove the battery for 1 minute and reinsert it. If it still blinks red, unplug the charger for 1 minute, plug it back in, and reinsert the battery.
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Clean the terminals if the fault remains, then try again.
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Test the charger with a second Kobalt 40V pack. If that pack charges normally, the first battery is likely defective. If neither charges, suspect the charger.
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Replace the battery if it still shows a charging fault after the reset.
If it still isn't working
- Warranty: the KRC 40-06 manual gives the charger a 3-year limited warranty. Check your battery's own warranty card for its terms, or contact Kobalt customer service.
- Replacement: if the battery is defective and out of warranty, replacing it is usually the practical choice.
Source
The LED meanings, temperature range and reset steps above come from the Kobalt KRC 40-06 charger manual (Lowe's, PDF). Kobalt's other chargers can differ, so check the manual that came with yours.
FAQ
What does a flashing red light on my Kobalt charger mean?
On the KRC 40-06, blinking red is a charging fault and solid red is over temperature. Use the reset in the steps above before you replace anything.
Can I use my Kobalt 40V battery in other Kobalt tools?
Kobalt 40V batteries are designed to work across the Kobalt 40V Max platform. A Kobalt 24V or 80V tool uses a different platform and a different battery.
How can I tell if my Kobalt battery is defective?
If it still shows a charging fault after the reset, and a second Kobalt 40V pack charges normally in the same charger, the first battery is the likely cause.
What should I do with a swollen battery?
A swollen battery is a safety hazard and should not be used or charged. Take it to a recycling center or a designated drop-off location.