How To Repair Cordless Tool Batteries

Lithium ion batteries are a wondrous invention that are lightweight and long lasting. But it's infuriating when the battery won't recharge. You stick the battery in the charger and … nothing. Guess what? You can fix these batteries that appear to be completely dead. Read on …

This post is NOT sponsored by Ryobi. They do not approve of or endorse this method for fixing a Ryobi battery. AT all.

Jump straight to the tutorial and how to video.

One of two things are going to happen as you read this post. You will either unfollow me due to my pathological boringness or … you will propose marriage. So get ready to act accordingly.

Since originally posting this tutorial a few years ago I've been hoping Ryobi would improve their batteries and chargers. So I was happy to see the development of the newer Ryobi P117 Intelliport Charger. It's supposed to do a faster and better job of charging your batteries but according to the reviews on Home Depot and Amazon they don't have this issue figured out quite yet.

What issue? I'll tell you.

If you have any sort of cordless power tool, but especially one powered by a Ryobi 18V battery, you have no doubt encountered the dreaded flashing red charger light. And if you haven't … you will. It inevitably goes like this – you run to the basement to grab your cordless drill because after 10 years of thinking about it, you're finally going to build that 4 level, Tudor style treehouse with kitchenette. Or you're going to hang a picture.

Either way you put your battery in the charger and all you get is a flashing red light, which according to the label on the charger means your battery is defective. It isn't just dead. It's "defective". I'm here to tell you you it isn't. You probably left it in the charger too long which weirdly drains the battery.

Your battery is fine. It just needs a little boost.

You Can Fix a Rechargeable Battery That Won't Take a Charge.

You heard me right. You do NOT have to buy a new $50 battery. You do not have to call the company and swear at them because this stupid "defective" battery is only 2 weeks old. (although by all means feel free to do so) You do not have to wait until they ship you a replacement battery to finish your project. You can get that battery up and working in about 5 minutes.

How to Fix an 18V Battery

What You Need

A lithium ion battery that won't charge. (duh)

An AC adapter (an old phone charger for example)

Common AC adapter on workbench.

A multimeter. (this is actually optional but helpful … if you don't have one don't worry, you can still fix your battery)

Multimeter on workbench with tools around.

Note: If you aren't used to doing this sort of thing, or using things like a "multimeter" this is going to seem crazy and hard and way out of your DIY league. It isn't.

Steps

Step 1. Cut the end off of your AC adapter. That's right. Just cut it off. It's for a 10 year old cell phone, you're never going to use it again anyway. It's frankly kind of weird that you saved it to begin with.

Cutting the end plug off of an AC adapter.

Step 2. Separate and strip off 1″ of each wire. You have *just* made booster cables! Good for you.

Positive and negative wires on AC adapter.

TIP:

Black wire = negative Striped or solid white wire = positive

IT IS VERY IMPORTANT TO NOT MIX THE TWO UP.

Step 3. Remove the screws holding the battery together.

For Ryobi batteries it's a star shaped screw head like this.

A few years ago I bought a kit of weird small screwdriver heads from Amazon. I initially bought it because I needed a special tip for removing my Macbook Pro cover to replace the battery. But I've used it for a ton of other stuff since getting this kit.

Tip of star shaped screwdriver.

TIP:

There's a hidden screw under a piece of plastic. You need to pry the plastic off to get at the screw underneath. I used a very thin screwdriver to pry it off.

Step 4. Pull the top off of the battery case.

Top removed from Ryobi Lithium Ion battery.

Step 5. Remove the 2 plastic side pieces. They're the things you press in to remove your battery from your drill.

Step 6. Lift the battery pack out.

Ryobi battery completely disassembled on workbench with charging cells removed.

Step 7.Set the Multimeter to read volts. For testing an 18 volt battery choose the 20 volts setting. This will give you the most accurate reading. (If you don't have a multimeter skip to Step 9 and hope for the best)

TIP

Volts are symbolized by a "V" with one or two straight lines over it on a multimeter so it's that section of the multimeter that you use. The section under the V with the straight line(s). Not the squiggly line. The straight line.

Multimeter on a workbench with a reading of zero.

Step 8. Touching the red probe to the positive (red) terminal and the black probe to the negative (black) terminal, read the voltage shown on the multimeter. In my case the battery was carrying a charge of 0.06 volts. Which is *almost* nothing, but not completely nothing.

Testing 18 volt battery cell with multimeter with a reading of 0.06

Step 9. Plug your AC adapter in and using the wires, boost your dead battery. Just touch the black wire to the negative terminal (the one with the black wire going to it) and the white wire (or striped wire) to the positive terminal (the one with the red wire going to it). Do this on and off for approximately a minute.

TIP

Apparently lithium ion batteries should be "pulse" charged. Which means you hold your wires down for 15 seconds or so, then release them. Then hold them down again. Over and over.

DOUBLE CHECK THAT YOU ARE TOUCHING POSITIVE TO POSITIVE AND NEGATIVE TO NEGATIVE.

Boosting an 18 volt battery with an AC adapater.

Step 10. Test your the voltage on your battery pack again. It should be higher than it was before boosting. (Again, if you don't have a multimeter don't worry about this – you'll just have to press on without one)

Mine went from 0.06 volts to 7.58 volts after a minute long boosting session.

Testing a cell on an 18volt battery with a multimeter with a reading of 7.58.

Step 11. Put the plastic cover back on the battery pack (just the part that goes into the charger) and set your battery on the charger to see if it will take a charge.

5 cells of individual batteries inside an 18 volt battery.

If you still only get a red flashing light and the battery won't charge, boost the battery some more. I find the battery charger will recognize that the battery is good again when you boost it to between 10 and 14 volts.

Checking the results of boosting a battery with a multimeter.

Just keep repeating the "pulse" boosting and testing the battery until it will finally be recognized by the charger and you get the green light.

To those of you who found this subject matter to be on par with spending 3 hours in a waiting room, sorry 'bout that.

For the rest of you? I know exactly how you feel. I felt the same way. Let me know exactly how elated you were after you brought your first battery back to life in the comments section.

Here's a 3 minute tutorial video showing me as I fix my own battery.

Cut the end off of your AC adapter. That's right. Just cut it off. It's for a 10 year old cell phone, you're never going to use it again anyway. It's frankly kind of weird that you saved it to begin with.
Separate and strip off 1" of each wire. You have *just* made booster cables! Good for you.
Remove the screws holding the battery together. There's a hidden screw under a piece of plastic. You need to pry the plastic off to get at the screw underneath. I used a very thin screwdriver to pry it off.
Pull the top off of the battery case.
Remove the 2 plastic side pieces. They're the things you press in to remove your battery from your drill.
Lift the battery pack out.
Set the Multimeter to read volts. For testing an 18 volt battery choose the 20 volts setting. This will give you the most accurate reading. (If you don't have a multimeter skip to Step 9 and hope for the best)
Touching the red probe to the positive (red) terminal and the black probe to the negative (black) terminal, read the voltage shown on the multimeter. In my case the battery was carrying a charge of 0.06 volts. Which is *almost* nothing, but not completely nothing.
Plug your AC adapter in and using the wires, boost your dead battery. Just touch the black wire to the negative terminal (the one with the black wire going to it) and the white wire (or striped wire) to the positive terminal (the one with the red wire going to it). Do this on and off for approximately a minute. DOUBLE CHECK THAT YOU ARE TOUCHING POSITIVE TO POSITIVE AND NEGATIVE TO NEGATIVE.
Test your the voltage on your battery pack again. It should be higher than it was before boosting. IF IT IS NOT, THEN STOP. YOUR CELL COULD BE DAMAGED AND CONTINUING COULD BE DANGEROUS.
Put the plastic cover back on the battery pack (just the part that goes into the charger) and set your battery on the charger to see if it will take a charge. If you still only get a red flashing light and the battery won't charge, boost the battery some more. I find the battery charger will recognize that the battery is good again when you boost it to between 10 and 14 volts.
Repeat the "pulse" boosting and testing the battery until it will finally be recognized by the charger and you get the green light.
Reassemble your battery. Your rechargeable battery is now fixed.

Black wire = negative Striped or solid white wire = positive It is very important to not mix the two up.
There's a hidden screw under a piece of plastic. You need to pry the plastic off to get at the screw underneath. I used a very thin screwdriver to pry it off.
Volts are symbolized by a "V" with one or two straight lines over it on a multimeter so it's that section of the multimeter that you use. The section under the V with the straight line(s). Not the squiggly line. The straight line.
Lithium ion batteries need to be "pulse" charged. Which means you hold your wires down for 15 seconds or so, then release them. Then hold them down again. Over and over.

Please direct marriage proposals to my publicist. A certain tool company is *not* interested in proposing marriage to me. So I'd like to make a point of saying I love these tools and use them all the time. Their batteries and chargers on the other hand, could use some improvement.

OTHER WAYS TO FIX THINGS.

How to Unclog Your Central Vacuum
How to Sharpen a Push Mower
How to Replace Carbon Brushes on Any Motor
How to Mend a Broken Fingernail (because you're surely going to need it after replacing carbon brushes)

Questions & Answers

Is there an easier way to do this? Possibly. Some people have had success with putting the battery in the charger and waiting for the red light to come on. Then you pulse charge the battery by quickly plugging and unplugging the charger.
What voltage does the charger need to be? A 12 volt charger will do the trick.
Isn't this dangerous? There is a small chance of BIG danger. So proceed with caution. If a cell doesn't immediately charge a little bit with this technique, stop. If anything (charger, cells, wires) starts to heat up, STOP.
How long will the battery last after fixing them this way?Until you accidentally leave it in the charger too long again, or until the battery's natural death.

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*Proceed with caution and follow instructions exactly. Failing to do so could lead to injury.*

$Have a Ryobi Battery That Won\'t Charge? You Can Fix That.$