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    Home » How To Stuff » How to (DIY)

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

    June 6, 2023 by Karen 459 Comments

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    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 ...

    Lime green cordless Ryobi drill.

    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.

    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. (I can teach you how to hang a picture too)

    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 it isn't.  You probably left it in the charger too long which drains the battery.

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

    This is where you want to go if you're looking for how to boost a car battery.

    Table of Contents

    • You Can Fix a Rechargeable Battery That Won't Take a Charge.
    • How to Fix an 18V Battery
    • Steps
    • How to Fix a Ryobi 18v Rechargeable Battery

    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.


    NOTE: First try pulse charging.

    Pulse charge your battery by plugging and unplugging your charger (with the battery in it) for 10 seconds. Try this a few times. If it doesn't correct the problem, continue on with this tutorial.


    How to Fix an 18V Battery

    What You Need

    • A lithium ion battery that won't charge
    18 volt rechargeable battery on workbench.
    • 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 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.

    Overhead view of a rechargeable drill battery on paint splattered work bench.

    For Ryobi batteries it's a star shaped screw head like the one below.

    A few years ago I bought a kit of small screwdriver heads from Amazon that has every small, weird, head you'd ever need.

    Tip of star shaped screwdriver.

    TIP:

    Would you like to save this stuff?

    We'll email you this post, so you can refer to it later.

    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.


    Side by side view showing you how to remove small cap on 18 volt lithium battery.

    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.

    Disassembling 18 volt lithium ion battery.

    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.

    Success with a green light on a Ryobi charger after pulse charging the battery.

    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.

    How to Fix a Ryobi 18v Rechargeable Battery

    You have an almost brand new Ryobi battery that the charger won't recognize and won't charge. Here's how to fix that.
    NOTE: Before doing all this, first try to pulse charge your battery by plugging and unplugging your charger (with the battery in it) for 10 seconds. Try this a few times. If it doesn't correct the problem, continue on with this tutorial.
    4.52 from 231 votes
    Print Pin Rate
    Total Time: 15 minutes minutes
    Servings: 0
    Author: Karen Bertelsen

    Instructions

    • 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.

    Video

    Notes

    1. Black wire = negative     Striped or solid white wire = positive It is very important to not mix the two up.
    2. 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.
    3. 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.
    4. 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
    1. 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.
    2. What voltage does the charger need to be? A 12 volt charger will do the trick. 
    3. 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. 
    4. 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.

    Seeing as you're the sort of person to make it all the way down here to the end of this post, you might like to learn how to install a battery operated electric fence around a home vegetable garden.

    *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.

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    1. Dan

      April 10, 2025 at 1:39 pm

      Great information but when should you realize a battery is dead beyond resurrection?

      Reply
      • Karen

        April 11, 2025 at 10:01 am

        Hi Dan. This method is for using when you have a fairly new battery that you know should be accepting a charge. If it's 5 years old and has gone through a ton of charge cycles then it's probably just ready for replacement. ~ karen!

        Reply
        • Dan

          April 14, 2025 at 11:11 pm

          OK, thanks for your swift reply! Don't know how I found your site but I'm glad I did!

    2. BED

      February 24, 2025 at 8:41 am

      Wow, thanks a lot Karen. Just performed the short-cut method (quickly unplugging and re-plugging the charger) and after the 3rd or 4th cycle my 18v Ryobi battery started accepting a charge. Stumbled onto your cite with the battery issue, but will definitely be checking the rest of it out. Thanks again!

      Reply
      • Karen

        February 24, 2025 at 11:01 am

        Excellent! I'm glad the easy way worked for you. ~ karen!

        Reply
    3. tg

      February 05, 2025 at 12:59 pm

      Great tutorial. And it worked - thanks Karen! Saved one more from the landfill! Went a step farther by jumping each of the individual cells separately, and it quickened the process. Just make sure you mark the positive end of each one. Back to 18 volts again!

      @Jason Kerr: if the plugging and unplugging doesnt work, using the jumper on the vertical peg does not allow the full volvtage to get to the batteries, due to the circuitry.

      Reply
      • tg

        February 06, 2025 at 7:27 pm

        Followup: Just remembered I had a lots older Ryobi battery pack sitting in the garage, in the recycle area, that has been there, dead, for several YEARS, same symptoms. Just applied this fix, and it's charging again! thank you again, and again! Wondering if this can be applied to other battery packs. Cheers!

        Reply
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    My name is Karen Bertelsen and I was a television host. In Canada. Which means in terms of notoriety and wealth, I was somewhere on par with the manager of a Sunset Tan in Wisconsin.

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