The charger simply blinks at you and the drill ends up being completely dead twenty minutes before you were meant to leave. Before you go to the store, remember that most batteries which 'won't charge' are not actually defective.
Usually the cause is either heat or dirt. A pack that has just been used and is still warm will deliberately refuse to charge, and a dirty contact is completely unable to conduct current. Carry out the seven steps in order and by the fourth step you will know if the problem is with the battery, the charger, or simply the weather.
Here is the step-by-step solution for a power tool battery that isn't charging, aimed at a workbench situation rather than a laboratory setting. Each step will take one or two minutes, and by the time you reach step seven you'll be able to decide whether to repair it or replace it. If you'd like to know something about how batteries work before you begin, then see our electric tool battery guide.
Step 1: Let it cool down
If the battery has only just been removed from the tool, then that is very probably the real issue. Lithium batteries are deliberately designed to refuse charging when they're hot in order to protect the cells inside. The Ryobi support pages state that the safe charging temperature is about 10 to 37°C, and Worx advises customers to wait until the battery is flashing and has cooled down below 42°C. Putting it simply, leave it for half an hour on the bench and then try charging it again.
More batteries that are deemed 'dead' are in fact just hot batteries, and that is the kind of July phone call that we most frequently answer.
Step 2: Clean the contacts
If the cooling isn't the problem, check the metal; sawdust, drywall dust and grime build up on the battery terminals and in the charger's grooves, and a loose connection appears just like a dead battery. You should first unplug the charger and then use a dry cloth to wipe both sets of contacts, those on the battery side and those on the charger side. Bosch's own troubleshooting procedure states precisely this: clean the contacts and make sure they are dry.
Then seat the pack and try again. A lot of batteries come back to life right here.
Step 3: Reseat it and check the outlet
To be half-seated is not to be seated. Insert the battery until it clicks or until it reaches the end of its travel, and don't rely on the first slight stop. From the charger's point of view, a battery that is a quarter of an inch out looks just the same as one that is dead.
First check the power supply by inserting a lamp or some other item you have confidence in into the same outlet. Chargers tend to fail without making much noise and they don't last as long as people think. So test the charger before you lament the battery.
Step 4: Cross-test to name the culprit
At this stage you are carrying out isolation procedures; if you have a different charger, then take the suspect battery and put a good known battery on the suspect charger. One of three things will then occur:
| Result | Culprit |
|---|---|
| The suspect battery charges fine on the other charger | Your charger, or its outlet |
| A known-good battery also fails on your charger | Your charger |
| The suspect battery fails everywhere, the good one charges fine | The battery |
Should the charger be found guilty, that will be the least expensive of the three solutions. If the battery fails in all cases, proceed to step five and then on to the verdict.
Step 5: Read the charger lights
The Chargers communicate in blinks and the vocabulary is approximately the same for all brands. Although the patterns do differ according to model, regard this table as representing the usual grammar and the manual of your specific charger as being like a dictionary:
| Light pattern | Usually means |
|---|---|
| Solid or pulsing green | Charging, or fully charged |
| Flashing red, no green | Pack too hot, too cold, or over-discharged. Wait, or see step 6 |
| Flashing red and green together | Defective pack or charger. Cross-test to split them |
| No lights at all | No power reaching the charger. Back to step 3 |
Step 6: Check for over-discharge
A battery which has not been in use for months may drop below the voltage level even when the charger is trying to detect it. The charger then remains dark or displays an error message not since the battery is faulty, but because it is asleep below the detection threshold.
This is the part where you have to resist the internet. Various forums advise you to jump-start the pack using a different battery or to open it up and charge the cells directly. Don't carry out either of those actions. The Power Tool Institute's guidelines on battery safety are clear in stating that a damaged or deeply discharged pack should not be forced back to life, and that fires occur because people open up the pack in an attempt to repair it. The safe solution in the case of a pack that has been dormant for months is to replace it, and that is generally the straightforward answer as well. In order to prevent packs from ending up in this situation, our article on how to store power tool batteries talks about this habit.
Step 7: The verdict
Time to sentence the patient.
Replace the battery if any of these hold:
- The cross-test pinned the battery, and it's more than a couple of years old. Black & Decker's support pages put the typical lithium pack life at two to three years, or 300 to 500 full charge cycles, whichever comes first.
- It charges for five minutes, then errors out. That's a cell that won't hold, not a fixable contact.
- It's under warranty. A pack that failed inside its warranty window is the seller's problem, not yours. Read the warranty page before you read this guide again.
Fix or wait instead if:
- It was just hot or dirty, and one of the earlier steps revived it.
- The charger is the guilty party. A new charger costs less than a new battery, and a working pack deserves one.
If the pack is done, the two guides that help most are signs a battery is done, for the full symptom list, and how long power tool batteries last, for the numbers behind that two-to-three-year figure. When you're ready, you can browse replacement batteries by brand across the twelve platforms we stock.
Common questions about a battery that won't charge
Why is my power tool battery not charging?
Usually heat, dirt, or a seating issue. Let a warm pack cool for about half an hour, clean the contacts on the pack and the charger with a dry cloth, and make sure it's pushed all the way in before you suspect anything worse.
How do I know if it's the battery or the charger?
Cross-test. Charge the suspect pack on a different charger, and put a known-good pack on the suspect charger. If the good pack charges, the charger is innocent. If the suspect pack fails everywhere, it's the battery.
What do the lights mean on my charger?
The usual grammar: green means charging or full, flashing red alone means too hot, too cold, or over-discharged, and red and green flashing together usually means a defective pack or charger. Patterns vary by model, so the charger's manual is the final word.
Can you fix a power tool battery that won't charge?
Not by opening it. The heat and dirt fixes are safe and they resolve most failures. Opening a lithium pack, or jump-starting a deeply discharged one, is how fires and injuries start, so the safe fix for a truly dead pack is a replacement.
Is my battery dead or just stored too long?
Both, usually. A pack stored empty for months can fall below the voltage where the charger can even detect it, and at that point the honest answer is replacement. Storing packs partially charged, in a cool dry place, prevents the whole problem.
Seven steps and the culprit will be identified almost every time—first heat, then dirt, then seating, then power, followed by the cross-test which settles the issue on either the battery or the charger, then the lights, and finally the sentence. Most of the packs are repaired before the sixth step; those that reach a conclusion after the cross-test are finished and the solution in this case is to replace the pack, not to use a screwdriver.
References & Sources
- Power Tool Institute battery safety guidance (Power Tool Institute, the power tool industry's safety association)
- Ryobi support (charging temperature and LED behavior guidance)
- Bosch support (contact cleaning and battery seating guidance)
- Worx support (cool-down temperature guidance for flashing packs)
- Black & Decker batteries lifespan support article (Black & Decker support)
Need a replacement?
If the verdict is to be replaced, you can look at the replacement batteries by brand. Since we carry compatible sets for twelve tool brands, the correct component has already been arranged for you and any questions can be directed to a real person via our contact page.