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.
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.
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
- An AC adapter (an old phone charger for example)
- A multimeter. (this is actually optional but helpful ... if you don't have one don't worry, you can still fix your battery)
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.
Step 2. Separate and strip off 1" of each wire. You have *just* made booster cables! Good for you.
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 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:
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.
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.
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.
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.
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.
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.
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.
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.
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.
How to Fix a Ryobi 18v Rechargeable Battery
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
- 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.
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.*
Ei Con
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
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.
Vince
Connect your DVM to the 2 wires coming from the charger. If voltage reads positive you are all set. If voltage is negative then you have it backwards. Mark the + wire from charger when read voltage is positive.
Rob
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
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
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
(but that's just a guess) Either way, don't try to charge it from the stem. ~ karen!
wildb
Reread Rob above. :)
Mike
Love the Santa Claus scissors!
Lara
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
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
Loving it! Thank you!!!!!
Annie
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!
Caroline
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 🤣
maggieb
Will have to drain a battery on purpose just to have the fun of trying this out!!!
Tanya
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.
PMMK
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
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
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
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
Wow! Heady but handy info!
Che
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
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
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!
Maria
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!
GREAT VID!
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 )
Sue
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
I changed the battery in my Macbook Pro. I linked to it in the post. I've never changed an iPad battery. ~ karen!
kddomingue
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
Well THAT made me Laugh! :D
Karen
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
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.
Martha Doane
My husband Jim(of exploding battery fame) wants to remind you all to wear safety glasses! Want to guess why?? :)
Mark
Your publicist is going to want more money now after being inundated with all the calls... :)
Bobbie
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
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
Didn't see the video either. Using chrome.
Karen
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
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
nope, no video. on Chrome. nada. nothing. Excuse me while I go buy a multimeter. Always wanted an excuse to do so.
Maria
Fascinating! Cool! Brilliant! Thanks! No vid :'(. I wanna see the vid :)
Karen
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
Hi Karen,
So am I and it isn't. Sorry.
Karen
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
Thanks Karen, it worked a treat, I really like your style.
DGr.
Karen
Perfect! :) ~ karen
Garnet
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.
Karen
Perfect. I'll await the call about from the call about your call. ~ karen!
Suel Anglin
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.
Karen
Ha! We are an industrious sort. ;) ~ karen!
Bruce Watson
I was stationed in Newfoundland with the United States Navy back in the late 60s...and I did find the locals 'industrious' as you state. Love this article and indeed, sign me up.
Gayle M
Clear! (zap)
Fun article. Thanks again, Karen.
Caryl
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
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
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
My dewalt 20 volt did the same thing and we had to fix them
Nathan
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
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
#3bosch/bostic
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
Ridgid Batteries,Lifetime warranty
Ed
I have begun switching my tools from ryobi to Ridgid, for the lifetime warranty which includes the batteries.
Tew
Caryl, you are right. About everything. Well said....
Gee Willikers
I haven't had trouble with my Ryobi yet, but jow Im prepared. Thanks
Gee Willikers
Now*
Mr John Harwood
I preferred jow...
Karen McDaniel
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
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
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
Consider the force respected. ~ karen!
Paul
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
Voltage doesn't kill. Current does. As long as it's under 10mA you should be fine.
Tyler
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
My house fire started with batteries left in an old TV remote.
TerryA
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
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
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
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
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
Karen
That's interesting! Thanks John. ~ karen!
Kristie L Marshall
I would love to see a photo!
liza
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!