Impact Driver Battery Not Charging
You drop the pack on the charger and get a flashing light instead of a charge. Most of the time it is temperature, dirty contacts or a deeply drained pack, not a dead battery. Here is how to read the lights and work through the fixes.
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When an impact driver battery is not charging, read the charger light first: it usually tells you whether the pack is too hot or cold, waiting, or faulty. Let a hot or cold pack reach room temperature, clean the contacts, reseat it firmly and try another outlet and another battery. A pack that still flashes a fault code on a known-good charger is usually finished. Never try to jump-start a damaged or swollen pack.
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Quick diagnosis: impact driver battery not charging
| Symptom | Likely cause | Fix |
|---|---|---|
| No lights at all | Outlet, cord or charger fault | Try another outlet; check for a tripped GFCI; test another charger |
| Temperature light or code | Pack too hot or too cold | Bring to room temperature; charging usually resumes on its own |
| Fault code on one battery only | Faulty pack, dirty contacts or deep discharge | Clean contacts, reseat, leave on charger; replace if it persists |
| Fault code on every battery | Faulty charger | Test those batteries on another charger; service or replace the charger |
| Charges, but runs flat very fast | Worn cells | Replace the pack |
| Shows full, tool will not run | Tool problem, not battery | See impact driver will not turn on |
| Swollen, cracked, wet, hot or smelly pack | Damaged pack | Stop. Do not charge. Recycle safely |
If the battery charges fine and the tool still does nothing, the fault is elsewhere; see impact driver will not turn on.
Charger light codes by brand
Charger lights differ by model, even within one brand. The meanings below come from manufacturer manuals where we could confirm them. Most chargers also have the codes printed on a label on the charger itself. Always trust that label or your charger's manual over a generic chart.
| Brand | Charging | Full | Hot or cold | Fault |
|---|---|---|---|---|
| Milwaukee M12/M18 | Solid red | Solid green | Fast flashing red | Flashing red and green |
| DeWalt 20V MAX (many chargers) | Blinking red | Solid red | Yellow light with blinking red on models with hot/cold delay | Fast blinking red |
| Makita 18V LXT | Red | Green | Check the label on your charger | Check the label on your charger |
| Ryobi ONE+ | Codes vary between charger models. Check the label on your charger or its manual. | |||
Milwaukee: from Milwaukee's M12/M18 charger manuals, which also list slow flashing red as charge pending. DeWalt: from DeWalt charger manuals; the yellow delay light is listed for models including DCB107, DCB112, DCB113 and DCB115. Two-stage and fast chargers use different patterns. Makita: from the DC18RC/DC18RA manual. Other Makita and Ryobi codes could not be verified across models.
One pattern holds across brands: a temperature code is not a fault. The charger is protecting the cells and will usually start by itself once the pack is in range. A fault code that repeats after the checks below means the pack or charger needs replacing.
Step-by-step fixes, easiest first
1. Check power
Plug a lamp or phone charger into the same outlet. Garage and outdoor outlets are often on a GFCI that has tripped. Avoid long, thin extension cords and generators with unstable output.
2. Let the pack reach room temperature
A battery straight off a long run of lag screws is often too hot to charge. One left in a cold truck overnight is often too cold. Bring it indoors and wait, typically 30 minutes or more. Do not put it in a freezer, oven or near a heater. If packs come off the tool hot all the time, see impact driver overheating.
3. Clean and inspect the contacts
Remove the battery. Look at the terminals on the pack and the charger for dust, debris, corrosion or bent contacts. Blow them out with compressed air and wipe with a dry cloth. Do not use metal tools inside the terminals. Then seat the pack fully until it clicks.
4. Swap to isolate the problem
Try another battery on the same charger, and the suspect battery on another charger of the same brand. That tells you in two minutes which part is faulty.
5. Leave a deeply drained pack on the charger
Lithium-ion packs left empty for months can drop very low. Many chargers start these with a slow recovery charge and may show nothing useful for a while. Leave it on the charger, nearby, for a reasonable period. If it still reports a fault, it is done.
Safety: Never try to jump-start a battery by connecting it to another battery, a car charger or a bench power supply, and never open a pack. Bypassing the pack's protection can cause fire. Stop immediately and do not charge any pack that is swollen, cracked, wet, unusually hot or smells of burning. Store it outside on a non-flammable surface and take it to a battery recycling drop-off.
When to use the warranty
Batteries and chargers often carry their own warranty terms, which can differ from the tool's. Check the manufacturer's current terms for your exact battery and charger, and register them if required. If a pack shows a fault code on two known-good chargers, or a charger fails on several good packs, contact the brand or an authorized service center. Keep your receipt. Battery-specific notes are in the Milwaukee M18 battery guide and the DeWalt 20V battery guide.
Third-party adapters and chargers can complicate a claim and may not handle a deeply drained pack the same way. If you use them, see cordless tool battery adapters for the risks.
M18 batteries on Amazon DeWalt 20V batteries on Amazon
Prevention: keep packs healthy
- Do not store packs empty. Recharge soon after use, and top up long-stored packs every few months.
- Store cool and dry, not in a hot truck cab or a freezing shed. More in how to store cordless tool batteries.
- Let hot packs cool before charging rather than waiting on the charger.
- Keep contacts clean and use the covers if your batteries came with them.
- Do not drop packs. Internal damage can show up later as a fault code.
- Rotate packs so one does not do all the heavy work.
For capacity, platform and replacement choices, see the impact driver battery guide.
Frequently asked questions
Why is my battery flashing red and green on the charger?
On Milwaukee M12/M18 chargers, flashing red and green indicates a damaged or faulty battery pack, according to Milwaukee's charger manual. Clean the contacts, let the pack reach room temperature and try again. If it repeats on a second charger, the pack needs replacing.
How long should an impact driver battery take to charge?
It depends on the battery capacity and the charger's output. A small compact pack on a fast charger may take well under an hour, while a large pack on a basic charger takes longer. Check the charging time chart in your charger's manual for your exact combination.
Can a completely dead lithium-ion tool battery be revived?
Sometimes a deeply discharged pack recovers if left on the charger, since many chargers start with a slow recovery charge. If the charger reports a fault, do not try to force a charge with another power source. Bypassing protection on a damaged lithium-ion pack is a fire risk.
Is it bad to leave a battery on the charger?
Modern brand chargers stop charging when the pack is full, and manufacturers generally allow it. For long storage, though, packs last longer kept partly charged in a cool, dry place rather than sitting full on the charger for months.
Will an off-brand charger work with my battery?
Some third-party chargers fit, but they may not communicate with the pack's electronics the same way, and using them can affect your warranty. A brand charger is the safest test when diagnosing a charging problem.