Quick answer
- Kobalt's published manuals do not document a four-red-light pattern on the battery. We could not find a manufacturer source for what it means, so we will not guess.
- The charger lights are documented. On the Kobalt KRC 40-06 (40V Max) charger, blinking red is a charging fault and solid red is over temperature. Blinking green means charging, and solid green means fully charged.
- Put the pack in a charger and read the charger's light. That is the reading you can act on.
- If the charger shows a charging fault, 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.
- For an answer specific to your pack, contact Kobalt customer service at 1-888-3KOBALT.
Symptoms
- Four red lights flashing on the battery itself.
- A tool that will not run, or one that stalls or cuts out under load.
- A pack that feels hot or cold.
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). Below 45°F or above 104°F, move the charger and battery to a room-temperature spot.
- Damage: look for cracks or swelling in the case and corrosion on the terminals.
- Seating: make sure the battery is seated in the tool and the contacts are clean.
- Charger: put the battery in a Kobalt charger and read its light. Try another battery in the same charger to rule out the charger.
- Age: if the pack is old, it may be at the end of its life.
Step-by-step fix
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Remove the battery from the tool.
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Inspect it for damage or corrosion. If you find any, replace it.
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Let it reach room temperature. If it is hot, let it cool. If it is cold, warm it up before using or charging it.
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Clean the contacts on the battery and the tool with a clean, dry cloth.
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Test it in the charger and read the charger light. If the charger shows a charging fault, do the reset from the Quick answer. A battery that still shows a charging fault after the reset is defective, according to the KRC 40-06 manual.
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Replace the battery if the fault stays.
If it still isn't working
Check whether the battery is still under warranty and contact Kobalt customer service at 1-888-3KOBALT. The battery has its own warranty terms, so check its card or the label. If the warranty has expired, a replacement battery is usually the practical choice.
Source
The charger light meanings, temperature range and reset steps come from the Kobalt KRC 40-06 charger manual (Lowe's, PDF). We found no Kobalt manual that describes the battery's own four-light pattern.
FAQ
What does it mean if my Kobalt battery has four red lights flashing?
We could not find a published Kobalt meaning for that pattern. Check the charger light and contact Kobalt for your specific pack.
Can I charge my Kobalt battery if it's cold?
The KRC 40-06 manual says charging begins once the pack is between 37°F and 117°F (3°C to 47°C). Let a cold pack warm to room temperature first.
How long should I wait if my battery is too hot?
Let it cool, ideally in the charger, until it is back within range. The manual does not give a fixed time.
Is there a way to fix a damaged battery?
If the battery shows physical damage, replace it. Attempting to repair a damaged battery is dangerous and not recommended.
How can I tell if my charger is working?
Test it with another battery. If it charges another battery without issue, the original battery is likely the problem. If it fails to charge any battery, the charger may need replacing.