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

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.

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

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 and hard and way out of your DIY league.  It isn’t.  


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.


Black wire = negative     Striped or solid white wire = positive


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 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.


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)


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.


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.


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.
4.63 from 54 votes
Print Pin Rate
Total Time: 15 minutes


  • 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.



  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.


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.


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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.


  1. John, 2 way guy says:

    The pulse charge will work unless a battery is worn out. Lithium batteries can only take around 500-750 charge cycles on average. The nickel metal batteries were more. The pulse will work on lithium, nickel metal (NiMh) and NiCad. I have a professional charger that does exactly this procedure. My charger was designed for cell phones. The pulse works better on the older types, but I have used it for years for my own tools. I love the simplicity of your solution, I would do the power “pulse” for 2 minutes and not be discouraged until it took over 10-12 minutes. A word on quality: typically more expensive batteries do use better quality batteries inside. For instance, a $15 battery should not work as well as a $50 battery. For Chinese batteries, well, uh, they are not into quality control like the Japanese or Korean companies. “Nuff said!

    • Frank woodall says:

      I skipped from the middle step 9 to step 11. Once the battery is in the charger then use your 12 volt DC source to trick the charger into thinking the battery has enough charge to start the charger. Touch + lead to positive end of battery pack and – lead to negative end of pack. A couple of seconds will start the charger. Let charge for a few then reassemble battery and finish charging battery.

    • Mark says:

      My batt is reading 17.2v but when I place it in the charger all I get is continuous red flashing testing light this is after I have cleaned all terminals and posts

  2. Joseph Cutajar says:

    I use another solution to revive dead rechargable batteries in the case that they are not recognised by the charger due to very low voltage. One could use another battery with a slightly more voltage than that you have, and using the same principle as indicated above – positive to positive and negative to negative and many times it will work. I hope this helped.

    • Ed says:

      Sounds like a bad idea to me. The pulse charging with an old wall brick is good because chances are, the wall brick is current limited. Charging a dead batt with a good batt may produce an overcurrent situation and damage the batts, cause sparks, and/or cause fire.

  3. Rudolph says:

    Just to let you know: If above is not working after all, you can buy replacement cells very cheap at the wellknown Chinese website’s which I will not mention but start with ali and end with baba and so on. You need half an hour spare time and a soldering tool and you have a new batterypack (with probably more capacity then before) for less than 10,-

    • Joseph Cutajar says:

      That could be another solution, only if the batteries have good amperage. Besides the voltage the amps for the batteries need to be good and correct as indicated on the cells. Sometimes these are not true at all and you will find out later that the charge won’t last as long as the original ones.

  4. william williams says:

    I have used the “on/off/on/off” method on several batteries, and for the most part it works. My question is simply why bother taking the battery apart in the first place? There are easy to access + and – terminals without taking it apart. Thanks for the post, btw.

    • Ben says:

      I would venture a guess that you want to take it apart and pulse the batteries directly because some modern lithium batteries have computer controls built in to the battery. If the battery is almost entirely gone (reading close to zero volts as in the post) the controller won’t be able to read detect and relay power to the cells.

      But that’s just a guess.

    • Shadwell Banks says:

      Great technique thanks for sharing!!

      Yes – it is possible to do this without removing the casing. I zapped my Bosch drill battery without removing the casing and successfully revived it.

      This also worked on my Ikea battery screwdriver.

    • Mark Spohr says:

      I’ve done this without taking the battery apart.

  5. David says:

    Girl you are the bomb

  6. Pablo says:

    Cara Karen,
    My name is Pablo and I am very swarthy but I smell okay. I made my battery like you show in the pictures and now is work too well. So thank you for save me one hundred fifty dollars. Your feet make me crazy. Gracias e buenos dias, Senorita.

    • Jimmy da Creek says:


    • Indawgwetrust says:

      Karen i hope you and Pablo have a lovely marriage and many beautiful children.

    • Michael G Crist says:

      ¡Prueba “Google Translate” la próxima vez!

      ¡Tu traductor realmente arruinó tus comentarios!

      ¡Pero estoy seguro de que “Karen” obtuvo el punto principal, que es su “arreglo” funcionó como se describe!


      Try “Google Translate” next time!

      Your translator seriously screwed up your comments!!

      But I’m sure “Karen” got the main point, which is her “fix” worked as described!!!

  7. Larry says:

    Karen, I’m new to your feed, but have several batteries I’m gonna try to revive at home using this info. I’ve been using Makita and Ryobi 9.6v to 18v power tools and batteries for several decades, and this would have saved me much money/frustration over the years. I’ll let you know how it goes. In the meantime…. I’m pretty certain my wife of 36+ years wouldn’t approve of my serious proposal of marriage to you, and your husband might not, as well, but just rest content that the sentiment is there. I can only imagine the joy of living with a wife who knows this stuff…….

  8. Bob Funk says:

    Does not seem to work on a WORX power tool 20v battery…unless I am doing something wrong. Has anyone had experience with this? Also, is it possible to hook these type batteries up to a Battery Tender Trickle Charger and have them be “pulsed” back to being able to charge?

    • Karen says:

      The last thing you can try is to put the battery in the charger and then plug it in and unplug it (the charger) repeatedly. This is in effect pulse charging. The only time the original technique wouldn’t work is if your battery is genuinely dead – a very old battery for example. ~ karen!

      • Greg says:

        This worked for me too! Simply plug in, wait a few seconds, and unplug. Do this repeatedly. Mine started taking the charge after doing it just 3 times.

        • Karen says:

          Good to know. I haven’t had an issue with mine since fixing them so I haven’t been able to test it out. ~ karen!

      • Chuck says:

        Just an FYI, I tried the insert and remove attempt and ruined the 40 volt expensive ryobi charger, bummer. The charger was only 2 years old and had to buy a new one. That battery never did charge even though I was able to charge it to 3 bars with a new battery, really expensive. Real bummer. Thanks for the info.

  9. Bob Funk says:

    If you can see and positively identify the + and – terminals on the battery, and access them, is there any reason you cannot just pulse charge them through the terminals?

    • Karen says:

      Hi Bob, if the problem with the charger not recognizing the battery is happening on the level of the board (in between the cells and the stem) then charging from the stem won’t fix the problem. And in most cases the problem is in the board. ~ karen!

      • TomT says:

        So after the pulse fix. Would we have to open the battery to redo this everytime it need to be recharge?

        • Karen says:

          No, no. The pulse fix kick starts the batter back into action. You just need to do it once. (unless you leave the battery in the charger too long again, lol) ~ karen!

    • ben dover says:

      I just tried the plug and unplug method and it worked – amazing. Took about a minute. now green and charging. Was about the throw it out.

  10. Cliff MCKAY says:

    thanks I will try this.

  11. Don says:

    In an effort to correct some erroneous numbers, each 18650 cell is not 1.3V, but more like 3.7V. Five cells in series (end to end) produces a roughly 18.5V battery pack, when fully charged. With the short-period contact with the output of a 15V wall charger, it is not likely that you will cause any damage to the battery pack. The charging can also be done with a 5V charger just by intermittently connecting the appropriate leads to the + and – end of each cell (the green tubes in the battery pack that look like small “C” size flashlight batteries). Be careful though, because you CAN overcharge each cell with a 5 volt charger. Check the cell voltage frequently, and make sure it doesn’t go over 2.6 volts. If you have any doubt with this way of charging them, DON’T DO IT! It could be dangerous. Go out and look for a 15V charger instead. It should only cost a dollar or two at a thrift store.

    Although it is wise to check the charger to make sure the output is DC and not AC, there aren’t many that output AC anymore. Look at the label on the charger – it will say something similar to “Input – 100 – 240V” with a squiggly line after it (which denotes AC voltage), and maybe” .2 Amps”, followed by “Output 5V” with a straight line with 3 dots underneath (denotes DC voltage), and maybe 1.2 Amps. The “Amps” numbers can be different from source to source, and indicates the amount of power the device uses and puts out. If it has the squiggly line (AC) after the output voltage, don’t use it to try to charge the batteries.

    • Bob Funk says:

      Do you mean that these batteries are DC, and we are not to try to use an AC charger to pulse them?

      • Robert says:

        Wooooooooooooo! Nice save on the little line with 3 dots is safe. The proper tell is actually power is watts, energy is volts, work is amps. Any current cell phone ZTE, GOOGLE, SAMSUNG will work any will see long as not more than bat., Preferably ¼-½ 3v use 3v-1.5v-.5v will work. I worship the ground you walk on Karen!

  12. Jeremie jaymes says:

    You my friend are a genius !! Keep up the great wrk

  13. Audrey says:

    I found you when I needed to change the motor brushes in my washing machine. I’ve stuck with you because you’re helpful and cheer me up. I’ve now fallen in love with you because of this post. Be still my heart.

  14. dav c says:

    How strong does the AC adapter need to be? I have a 5V one.

  15. Sandy Howell says:

    Those are 18650 batteries! I use them in just about everything these days. LED flashlights, Vape boxes, Makita chainsaw, Honda RoBo Lawnmower, every laptop I have ever owned, and all my USB chargers.
    Wow, I wonder how I can revitalize my batteries used in everything else (yes, I have a Ryobi cordless). I usually just buy new batteries and authentic 18650s are expensive. I prefer the higher mAh, the highest I have found is Panasonic 18650B, which are 3400 mAh high drain. Anything higher than 4000 is likely a fake- and there are lots of 18650 fakes out there, about 99%.

    The Ryobi appears to have Samsung 2250 with that shade of green casing. Those are a standard in many electronics.

    So what do you think? How can we recharge these batteries NOT in a battery holder?

  16. wes womble says:

    Thanks Karen; It made it even moor clear as I viewed you video. Great job

  17. Richard Dickenson says:

    That’s genius you are remarkable thanks for the great information.

  18. B says:

    I need the inverse- my multimeter was dead even with a new battery :(

  19. Renee Ryz says:

    Darn, wish I had seen this a month ago. I took the battery for my Swiffer vac in to a battery place where they will rebuild them – much cheaper – the guy put the leads on wrong, so when I plugged it in, blam blew up the circuit board, and out went a vac that was only a year old. I got a refund for the battery from them, but a new vac is $50 – I bet this would have worked. Whelp, I guess I will be using the ol broom again. I will show this to hubby though – he uses DeWault drills for work, but still good info!

  20. Carrie says:

    Thanks for this Karen – I love how you make these intimidating jobs look so manageable! One thing though- I tried to order the screwdriver kit you mentioned (one for my husband and 3 for gifts) but it links to amazon.com and I’m in Canada. Could you please link something similar from Amazon.ca? Thank you :)

  21. Blaine says:

    This is kinda sketchy… Charging damaged (which can happen if voltage is too low internally) or unevenly charged lithium cells can cause them to heat up and burst and then spew out flaming melted plastic and violent torch like flames. Charging voltage is also important as putting 18-20 volts from some random wall adapter into a single 1.3v cell could lead to the same disaster. Not all AC Adapters are created equal, some are AC output, be sure to read the printed data on the charger. A little more reading into lithium cells might be a good idea to better understand what state your cells are at before attempting to try this.

  22. Micah says:

    Pretty dangerous to try this. There is a high likelihood of fire or explosion depending on the state of the battery. What is described here is a very specific situation, and thinking this will work in general is msiplaced.

    As an engineer developing battery packs, I urge you not to attempt this. These can explode into flame, and burn you or your home. All those electronics you’re bypassing are there for a very good reason.

    • Blaine says:

      ^This guys right!

    • Karen says:

      Hi Micah! I appreciate your comment. It will serve as a warning to those who choose to not follow the very specific instructions I have included for this very specific situation. ~ karen!

    • Lohi Karhu says:

      With the method shown, and following comments that I made, it’s pretty safe…main thing is to limit the amount of current that could be delivered to the battery pack, and a small “wall wart” is not about to blow up an 18650.

      But, one MUST avoid short-circuiting the “open” battery pack!

      • Micah says:

        No, it’s not safe. A wall wart can easily charge a 18650 cell to above 4.2 volts which at best will just shorten the life of the cell, worst case you have a fire on your hands.

        Keep in mind the cells get more dangerous as you charge them. It’s not about current, even a 1 amp charger can blow up a battery. If the charger that’s designed for the pack isn’t working, there’s probably a reason for it. Just jump starting it isn’t a good idea.

        • Lohi Karhu says:

          Micah, I agree that directly applying an uncontrolled charge voltage to a Li-ion cell can be disastrous, and that charging above 4.2 V per cell is definitely bad, probably dangerous, BUT, the whole idea, as shown here, does not involve continuous application of the charge, it does not bypass the thermal protection, it does not connect directly to the cells, and the wires are definitely not “designed” to connect continuously to the contacts…moreover, Karen specifically suggested short pulses, and continuous monitoring of the pack voltage, and only providing enough voltage level to “turn off” the UVLO circuitry…if one ignores every part of this process, and connects directly to the points shown, this is still at a point where the primary safety mechanisms of the pack are functional. With the additional voltage point information that I provided for the pack UVLO (hopefully these numbers meet with your approval?) circuitry to properly activated/deactivated, there is a vanishingly-small danger of any significant adverse event occurring.

        • Lohi Karhu says:

          Micah, when all is said and done, a statement like this:
          “There is a high likelihood of fire or explosion depending ”
          is just plain wrong, misleading, sensationalist…
          I really don’t know how much experience you have at this technology, but this level of rhetoric is well beyond what is appropriate… maybe, something like:”not following the recommended procedure, or connecting voltages to points other than suggested, can result in damage to the battery pack, and danger of the battery pack catching fire”

  23. Audrey Duff says:

    Hi Karen – you’re fantastic – I read almost every one of your posts, and the great comments as well. You have a very entertaining following ;-)

    Re the video, when it didn’t work on Chrome, I got it to work on Firefox. Then when I went back into Chrome it showed up.

    I also want to commend you for not having the background music on at the same time you are talking. Very often I stop watching videos because the “background” music drowns out what the person is saying.

    Keep ’em coming!

  24. Flash says:

    hmmm I will try this. thanks

  25. Bruce E Arkwright Jr says:

    Even if you only have a 5v phone adapter, you can do the same thing, but go across the individual battery cell not the whole series of batteries…

  26. Kristina says:

    What I’m really wondering here is about that “tutor” treehouse. Is it one where a really smart owl in glasses lives, and people can go there to have him answer questions about stuff? (Forwarding this tutorial to my farmer husband for use in his shop. Very useful indeed.)

  27. Tina says:

    You never fail to amuse me!

  28. Lavada says:

    Bloody brilliant!!!!! Thank you.

  29. Alena says:

    I love my Ryobi to death. It’s not the big “muscle” kind like Karen’s, it’t the lil’ one that has the battery inside (i.e. it’s not removable). (It think it cost $19.99 or $29.99). It’s not the best thing since sliced bread – it is better than sliced bread. I hope it will not die on me; I am always amazed how long it holds charge.
    I put my entire IKEA kitchen together with it.

  30. Karin says:

    This is definitely MacGyver worthy! If my husband wasn’t so anal about not over charging our batteries I might get to try this…

  31. Ei Con says:

    This. Is. Great. Question though. On this charger cord you’ve mutilated, how do you know which of the stripped wires is the ‘positive’ one? If you accidentally use the wrong wire will stuff blow up?

    • Ross Heitkamp says:

      Use the multimeter to measure the stripped wires, then put black tape on the negative one to remind you. Often one of the wires will have a white stripe on it – usually the positive.

  32. Rob says:

    This is great, thanks for sharing! Is there a reason you have to take the battery cover off vs just pulsing the charger leads to the battery contacts the way the charger does?

    • Karen says:

      You have to charge the batteries at the source – the batteries, *before* it goes through the circuit board to the stem. My guess is doing otherwise could explode the circuit board. ~ karen!

      • Rob says:

        Because the diodes in the circuit board will only allow voltage to travel in one direction, if you try to boost from the stem it will not reach the battery. When charging on the factory charger unit, thats how the circuit board recognizes stored voltage and allows charging to complete the cycle…

    • Karen says:

      (but that’s just a guess) Either way, don’t try to charge it from the stem. ~ karen!

  33. Mike says:

    Love the Santa Claus scissors!

    • Lara says:

      Me too, Mike! And I also noticed Karen’s black fingernails, that were in the first few photos “natural” and then suddenly became blackened, only to go back to being au natural at the end of the instructions. What a woman!

      • Karen says:

        Ha! I fixed two batteries. One for photos and one for the video. I painted my nails for the video. Then I realized I forget to get a few shots and did a reshoot on some of the photos. Hence the “mixed” nails. Good eye! ~ karen!

    • Iysha says:

      Loving it! Thank you!!!!!

  34. Annie says:

    Thanks Karen, I’m trying this for sure. My husband has thrown out lots of those “dead” batteries over the years. I can’t wait to show him this!

  35. Caroline says:

    OMG! I actually have a Ryobi drill battery that is dead and was going out to get a new one. I’m going to give this a try today and then, if it works, a marriage proposal is definitely on the cards 🤣

  36. maggieb says:

    Will have to drain a battery on purpose just to have the fun of trying this out!!!

  37. Tanya says:

    Karen, YOU ARE BRILLIANT! I’m happily married (38 yrs. ) so I will continue to love & adore you from afar.
    Suel, Exactly! Full choir too…
    KDDOMINQUE, you are funny.

  38. PMMK says:

    O. M. G. This is such a game changer. I’m dizzy, I’m so excited! I always knew there HAD to be a way to get those suckers to work again. After all, they are called rechargeable, not disposable. I can’t wait to spring this one on my super smart physicist husband who just grumbles and sulks every time he can’t fix something – like a nearly new battery that won’t charge. I may even show him how to do it.

    I do have 2 questions.
    1 – Is there a minimum voltage that the AC adaptor should have.
    2- Does this method only work on lithium ion batteries or will it work on other older types without blowing them up? We may have some vintage stuff that could be revived.

    You are officially the smartest woman I know.

    I love you and he’s gonna love you too. No proposals though. One spouse is enough.

    • Karen says:

      I *believe* any AC adaptor would work. The lower the voltage the longer it may take to boost. The one I used was 15 volts but I’m sure it would work with a 5 volt one as well … it would just take longer to work up the charge. As far as using this method on something other than lithium ion batteries, I don’t know, so I can’t recommend you do it. Hope you still love me. ~ karen!

      • Stu says:

        I think that if you use a 5 volt adapter, it’ll only charge the battery pack up to 5 volts, and won’t be able to go higher. It worked for you because your adapter was 15 volts.

      • Der Karhu says:

        As Stu said…Karen: hoping that this is not too long a ” saga” for you, or your readers ;-)

        A cell phone charger will most likely NOT work, since they are, more typically, 5 to 6 V, BUT, a LAPTOP charger should work, or any charger rated at 12 V (probably would show 14-16 V on your multimeter) A laptop charger is about 19 V, since the laptop uses about the same voltage battery pack as your 18/20 V Ryobi/Bosch/Makita… you can see that there are 5 Lithium Ion _cells_ in your surgically-dissected battery pack.

        Fully-charged Lithium Ion _cells_ are 4.2 V, immediately after charging, but drop to about 3.7 V under load, for most of the battery pack “run time”. Normally, the battery pack protection circuits will shut off the battery at about 2.7 V to 3 V per cell (13.5 – 15 V for your 18/20 V pack of 5 cells), and allow charging, BUT, when the cells discharge to about 2.3 V each, the battery control system will shut them off, internally, to avoid further discharge from totally “killing” the cells; at that point, the tiny voltage that you see on your multimeter is from the tiny amount of “leakage current” getting through the “kill switch” circuit.

        Your method of pulsing the pack to get it back to work is, usually, a good one, and can also be used with some cell phones that appear to be dead, by connecting/disconnecting the charger every 10-30 seconds for a few minutes, this will “trick” the “kill switch” circuit into allowing a small current pulse into the battery pack, and it only takes a small bit of charge to get the cell voltage back above 2.3 V/cell (11.5 V for that 5-cell battery pack), which will allow the battery pack protection circuit to let charging begin.

        For a 12 V battery pack, which has 3 cells, the voltages will be more like:
        – “kill switch” at about 6.9 V
        – fully-charged about 12.6 V
        – normal voltage at end of run-time 8.1 V -9 V
        – In this case, any AC adapter with a rated voltage about 6 VDC should provide about 8 V with no load, which should be “good to go” to re-energize a 12 V battery pack.

        As usual, Karen, great work helping your readers to save some money, save some headaches, and, perhaps, feel the accomplishment of successfully applying “battery CPR” !

        Hopefully, adding a bit of information to the “mix”

        • Jane says:

          Wow! Heady but handy info!

        • Che says:

          Yes, thank you for mentioning this. I tried this with a random old phone charger without thinking about it. I realized it was only a 5V charger when it charged the batteries to 5V at the charging leads (which barely registered at 0.2V through the battery circuitry at the normal connections). Luckily I had a broken string trimmer 18V charger sitting around and that worked just fine.

        • Nelson says:

          Yay! Thanks for that Der, and Karen. Der, you should propose to Karen, cause you could be an exlosive pack of energy together (poor pun intended). WooHoo!

        • Robert says:

          Holy Schmidt! The only I saw you didn’t put in was almost electrical devices the listing is rated always by labs and engineers at Max rms is 80% if it’s true 100% to allow the circuits to work. Bravo! Bravo! I love FRAGGING love this site!

  39. Maria says:

    This is a reply to my original post, and a thank you to Karen for your response to my original post :).

    Firefox, no link to vid.
    Chrome. It took a while for the vid to even populate on the page (big blank space like on FF). BUT it did load!


    Karen, now you have a bunch of batteries so there is no excuse of putting something off because you ran out of juice!

    Thank you. (Looking on how to contact your publicist )

  40. Sue says:

    Seriously, marriage is not really an option for us, but I just this evening decided that I had probably charged the battery for my drill for the last time. And, I was cursing at the thought of spending big bucks for a replacement – which is not enough. I always like to have a backup – so $75 – $100. Definitely have to thank you for this tip and add it to my Pinterest DIY.
    But, did you say something about changing the battery of your iPad? Was this a post that I missed? Could you share?
    Thank you! Sorry about the whole marriage thing . . .

    • Karen says:

      I changed the battery in my Macbook Pro. I linked to it in the post. I’ve never changed an iPad battery. ~ karen!

  41. kddomingue says:

    Well, I’ll be damned. And here I was just about to go and buy two new batteries. Question. I have some older Ryobi batteries that will say that they’re charged but will give out after half a screw. And as we all know, half a screw is worthless. (tongue planted firmly in cheek!) Think this method will work on them?

    • Jenny W says:

      Well THAT made me Laugh! :D

    • Karen says:

      It could be those batteries are genuinely at the end of their life. :/ You can try but I’m not sure it’ll fix those. ~ karen!

    • Bruce says:

      Try giving them the ‘cold shoulder’ – put them in the deep freeze for a day or so, then leave them out to return to room temperature. It works with NiCad batteries, sometimes NiMh and such. Basically the battery can short out internally (NiCads grow metal fibers internally sometimes) and freezing/thawing the battery can make internals shrink & expand enough to break the short. If that fails, you can relatively easily replace the internal cells if you are a good with a soldering iron – the originals will be welded together at the factory with an ultrasonic welder.

      Sadly, some brands are now setting a controller chip so that if the battery pack fails it will permanently kill the battery pack, replacing or ‘jump charging’ the cell/s won’t help.

  42. Martha Doane says:

    My husband Jim(of exploding battery fame) wants to remind you all to wear safety glasses! Want to guess why?? :)

  43. Mark says:

    Your publicist is going to want more money now after being inundated with all the calls… :)

  44. Bobbie says:

    Karen, one of the last lines in your post says “Here’s a 3 minute tutorial video showing me as I fix my own battery.” I didn’t see a link to your 3-minute tutorial on your post. Any chance you can add a link to the tutorial to your post OR respond to me a link to your tutorial? I’d love to share it with my husband. I sure wish I’d seen this a couple of month ago before I gave up and tossed two battery powered vacuum cleaners that would no longer take a charge. Sadness.

    I’m an occasional reader, and I LOVE your blog. Keep the hacks, DIYs and the humor coming.

    • Karen says:

      Ack. Bad timing. The video should be there Bobbie. Try using a different browser. Safari is a notorously outdated browser if that’s what you’re using and often things don’t show up with it. Try Chrome or Firefox and let me know. ~ karen!

    • Mark says:

      Didn’t see the video either. Using chrome.

      • Karen says:

        Very strange. I’ve logged out and am viewing t he video like a “regular” reader and it’s there. I’ll look into it in the morning but as of now it’s a conundrum. ~ karen!

        • TucsonPatty says:

          I saw the awesome video and use Safari! I think the gremlins in the technology get bored and do stuff – not like Karen does stuff, but they do bad stuff and that is why the stupid techno gadgets do not work at times!! I am a professional and I know these things. Ha! Thanks for the video and instructions, Karen.

        • ecoteri says:

          nope, no video. on Chrome. nada. nothing. Excuse me while I go buy a multimeter. Always wanted an excuse to do so.

  45. Maria says:

    Fascinating! Cool! Brilliant! Thanks! No vid :'(. I wanna see the vid :)

    • Karen says:

      Hi Maria! There is indeed a video. :) Try using a different browser. I’m using Chrome at the moment and it’s showing up perfectly. ~ karen!

      • DGr says:

        Hi Karen,
        So am I and it isn’t. Sorry.

        • Karen says:

          You probably have an ad blocker running on your computer. It will stop things like videos. You can adjust your settings to allow this site to show ads. And any other blogs that you glean information from and wish to help keep them in business. ~ karen!

        • David Grundy says:

          Thanks Karen, it worked a treat, I really like your style.

        • Karen says:

          Perfect! :) ~ karen

  46. Garnet says:

    Excellent! Another of your brilliant ‘stuff’ I can steal.
    Now all I need is a 21st century cordless… anything.
    Meanwhile, I’ll have my publicist call your publicist.

  47. Suel Anglin says:

    This is great! I’m having a near-religious experience. To wit, this came into my mind:

    Hallelujah! Thine the glory.
    Hallelujah! Amen.
    Hallelujah! Thine the glory.
    Revive us again.

    I love Canada and all the people who live there.

  48. Gayle M says:

    Clear! (zap)

    Fun article. Thanks again, Karen.

  49. Caryl says:

    OMG this is tantamount to open heart surgery! I almost cried but then I had to stop and ask myself “How the hell did she stumble on this????? You’re crazy and we love you.

    • Karen says:

      No stumbling. Dedicated research after being INFURIATED with Ryobi batteries. After having my 5th Ryobi battery die in a year (1 old and 2 BRAND new batteries died within 2 weeks so the company sent me two more which promptly also died … ) I decided these batteries couldn’t possibly all really be dead. It just wasn’t mathematically probable. So I did a bit of research, tried a few things and BAM. A reliable method for fixing them. I’m SO glad I’m not the only one who finds this life changing, lol. ~ karen!

      • JD says:

        First, I loved this article…. A great plan for extending the life of expensive batteries!

        Second… Maybe it’s time so switch to DeWalt. I have batteries that are 10 years old and more that are still charging just great

        Subscribing and Saving, Thanks!

        • Ralph says:

          My dewalt 20 volt did the same thing and we had to fix them

        • Nathan says:

          My dewalt batteries have the same problem. This isnt a brand issue, it is a known li-ion battery issue. If you kill a li-ion too much, it doesnt charge until you do a process like the one described above.

        • Blake Barber says:

          Yeah only problem with this logic is when you are buying a desalt you are really buying a black and decker /Porter cable/Stanley product and the only thing stand out about them is the snappy yellow and black bumble bee color scheme and a thicker plastic housing not to say dewalt stuff isn’t ok,but in my humble (and professional for twenty + years )opinion,there are only three manufacturers of cordless tools that turn out a professional grade product that generally speaking will last years beyond the factory warranty #1makita
          #2 Milwaukee
          Everything else is housewife project grade …no offense to house wives I’ve seen some incredible stuff accomplished by housewives on a mission….but you drop that dewalt from a triple stack baker scaffold and it’s most likely not gonna matter of your battery will still charge or not because you won’t be able to find the spot where it plugs in….it’ll be in various locations around the drop zone

      • PK says:

        Ridgid Batteries,Lifetime warranty

        • Ed says:

          I have begun switching my tools from ryobi to Ridgid, for the lifetime warranty which includes the batteries.

    • Tew says:

      Caryl, you are right. About everything. Well said….

    • Gee Willikers says:

      I haven’t had trouble with my Ryobi yet, but jow Im prepared. Thanks

  50. Karen McDaniel says:

    Do you think this would work on a cordless vacuum? I have one that I loved but the battery will not charge. It’s not even a year old.

    I’m showing this to my husband who has multiple cordless tools.

    • Karen says:

      It will work with any lithium ion battery but you’ll could have different voltages. Most cordless tools are now around 18V. If the vacuum battery is lower than that it would just take less boosting to get it to be recognized by the charger. Good luck and let me know how it works for you. ~ karen!

      • mike mac says:

        always always always remove any jewelry when working with electronics or electricity. we are made of water, we are naturally conductive, we burn easly, lithium batteries are highly flammable. a little flat birthday card can set a garbage truck or a dump afire. respect the force.

        • Karen says:

          Consider the force respected. ~ karen!

        • Paul says:

          That is really silly. A 18 v battery poses almost no danger at all. We aren’t made of water. We have a pretty high resistance so it is difficult to get a meaningful shock below 50v. You could short the battery through a ring, but the worst you would get is a small hot spot.

        • Lawrence Hooten says:

          Voltage doesn’t kill. Current does. As long as it’s under 10mA you should be fine.

        • Tyler says:

          Correct, but voltage allows current to flow for a given resistance. Check your skin’s resistance with a multimeter and you’ll measure in the high 100,000s or millions of ohms.

          20 V / 100,000 ohms = 0.2 mA

          I promise you that your skin is much higher than 100,000 at any given time unless you’ve been swimming in saltwater. Just don’t do any electrical work when you’ve been swimming in the ocean or are wearing ECG electrodes :)

        • NoMoMa says:

          My house fire started with batteries left in an old TV remote.

        • TerryA says:

          The point this MIKE MAC is making is NOT that you could be electrocuted, at least I hope not, because you’re right, you’re not going to get electrocuted by a 20v battery pack.

          The danger here is that if you short a LiIon or LiPo or even some NiMH or NiCd battery, THE BATTERY can overheat and burst into flames. Your ring or other jewellery can easily cause such a short.
          So, the short version, if you will excuse the pun, is that if you short a battery, it can very easily erupt into an inferno, in seconds, and you will not believe just how violently these things can go off.

          Lithium based batteries, even when almost flat, store a huge amount of energy, not electrical energy, but chemical potential energy. They are chemical time-bombs. Once they heat up, they can melt or deform the insulating layers inside the battery cell causing an internal short, then the battery will ‘run-away’ and completely discharge in seconds generating a huge amount of heat, often it is enough heat to ignite the lithium or the other materials the cells are made of.
          This is what happens when peoples cell phone suddenly burst into flames in their pockets or in their bags. rember the Galaxy 7 and 8 scandal?
          If you do not know what I mean, search youtube for ‘lithium battery fire’. Most of these demonstrations are triggered by a nail or some other deliberate damage to the cell, but they will go up just as easily due to a short circuit, or heat.
          To bring this full circle, the reason you are here in the first place, because your battery won’t charge, is a safety precaution built into the battery pack. Before it will charge your battery pack, the charger checks the voltage IN the battery, it expects it to be ‘flat’ but flat for an 18v pack means it is down below 18v. So the charger expects the pack to be somewhere between 15-18 volts. Anything less and one cell may have failed, so the charger will simply refuse to charge it because it is ‘probably’ damaged or faulty. Each cell is normally 3.7v
          Imagine if there IS a short in a cell (and it hasn’t erupted) , the pack will show something like 13-14v. If the charger were to start pumping power into it, there is a VERY good chance the faulty cell would go WHOOSH, and take the other 4 cells with it.
          We are assuming we DON’T have a bad cell, and we are trying to bring up the charge ‘safely’ little by little. If the voltage in the pack doesn’t start rising, or the wires you are touching onto the ends of the batteries get hot, STOP!!!!!!! you have a BAD cell and this trick won’t work.
          But often, if a battery pack sits for a while, it will simply have dropped below that 15v threshold due to natural loss of charge. This is where this ‘boosting’ trick comes in, we are manually putting in a little bit of charge to get it back up to the point that the charger will accept it as a ‘flat’ battery and agree to charge to for us.
          NOTE: my 15-22v is very rough, and these thresholds will vary from brand to brand, so don’t take them as gospel. It might be 15.2, 15.5 or even 16 or 17v.

        • Joseph says:

          Mike Mac’s simple recommendation is that anytime you work with electronics or electricity is to remove any watches and jewelry. Any professional technician is taught this in their training day one. The danger wouldn’t be just from the batteries, but the plugged in power supply as well (with the stripped wires). Also, the average human body is made up of 60-70% water… Google, it :)

          Oh, and thank you Karen for such a wonderful video. I was wondering how you were able to blur out certain things on videos. I thought that was pretty neat. You took a lot of time in making this and it shows.

      • Roger Lahti says:

        Just came across this tip. Pardon me if I’m applying too much reason to the issue but why are you tearing the battery cover off to get to a positive and negative connection when you already have ones accessible? The two exterior contacts of either side of the plugin arm are positive and negative. You only need to establish which is which. I will try the tapping trick to a dead lithium Robin battery I have to see if it works but this trick will work to get a Nicadbattery taking a charge again, and no need to tear it apart. Use a battery charger at the 2 amp setting or just put the battery into its normal charger and tap plug the charger into an outlet quickly several times, the proceed to recharge.

        • Karen says:

          Because you wouldn’t be charging the cells prior to it going through the circuit board. You need to charge the beginning of the process (the cells), not the end (the stem). For one thing, it’s between the cells and the stem that the problem is occurring, which is why when you try to charge it in its regular charger (through the stem) it doesn’t work.
          ~ karen!

      • John van der Heyden says:

        Hi I had the same problem with Black and Decker 12 v battery – the charger died so I bought another second hand and it died too. Today I hooked the battery up to a small 12 volt solar panel charger and it’s alive! Just clipped the positive on to the larger panel on the battery and the negative onto the other clip and it’s all go. Happy to share photo if that helps. Cheers. John

    • liza says:

      I have been on the fence about buying a cordless vacuum for this very reason. If Karen’s ‘hack’ works on a cordless, this will change my life!

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