Back from the DEAD! Lithium Batteries! 

So I bought a lot of about 11 batteries, and some other misc milwaukee tools. for like $350. I think the seller was trying to pull a fast one on me. All batteries were so low that one light wouldn't light up. After watching this I charged them ALL. Jokes on him now. 1x M12 with that 1H saw, 2 M18 Circular saws, 11x2AH Batteries, 1x60V DeWalt and 1x6AH DeWalt oh and a DeWalt abrasive cutoff saw(needed 9 dollar brushes, why on a new saw I dunno) all of it was brand new. All works now. Boy I owe you guys one for sure.

Excellent video I've watched several being an electrical engineer you're the only person who covered gauge of wire. The only other thing I would recommend is to put in a inline fuse. Thanks for sharing.

Love it! I did the same setup to charge my 10 year old stream light battery and it brought it back to life. I started off with 0.159 millivolts when I last checked it it was at 2.9 volts. I had to my new battery to trick the charger into sensing the battery voltage from my new battery to charge my old battery once it started sensing 2 volts I started charging my old battery directly with the charger.

Another, (potentially safer), way to charge a battery is to get a power supply off of eBay. You can set the correct voltage for your battery and supply a low current trickle charge to bring the battery up to a higher voltage. This avoids the chance of pumping a large current from the host battery into the low battery which could be hazardous. I would recommend using 0.5A or less so as not to damage the cells. You can often bring a battery up to a level that the OEM charger will accept within a matter of minutes. A 30VC 3A power supply can be had for less than $40 shipped and can useful for other projects as well.

Great info. I have two DeWALT 40v batteries. One of them stopped charging last year and I didn't want to spend the $192 to replace it. For some reason I held on to it thinking I would be able to take it apart and replace the guts of it. Well, now with this video, I followed your instructions and wired it up initially for 5 seconds and it pushed it up from 36.9 to 38.1 and now it's charging. Thanks for the detailed explanation of what happened and why it wasn't working. Hope all is good with you.

Great content. Also great delivery. You've got the right voice for it, tempo is good, diction is great. Thanks for doing this.

Thanks for the tip. I have also seen this when you leave a battery on the shelf for year and then go to charge it and it is below the cutoff voltage. One warning I would have when you connected the two batteries together is that a power resistor in series would probably be a good idea to limit the current. I'm guessing that most battery packs already have something like this in the circuitry but some cheap ones may not.

KEEP DRY SAND NEARBY FOR LITHIUM BATTERY FIRE CONTROL Do NOT use water to try to put out any lithium battery fire that occurs. That includes some fire extinguishers. Water can in fact make lithium-based fires much worse and/or cause explosive projection of flammable material to nearby objects/people/pets. Keep a fairly large amount of sand or dirt on hand to smother any lithium battery that starts to smoke or is on fire, or that you hear start to "crackle", or if you see it start to discolor/blacken. Also, I would keep a separate appropriate fire extinguishing method on hand to help control/put out any secondary fire(s) that are not adjacent to the battery itself (e.g. if fire spreads to grass, trash, clothing, or other objects). Because lithium battery fires can be VERY fast, explosive, and quickly spread and "jump" over small areas of cleared ground into nearby brush, furniture, etc...I'd personally keep handy an extinguisher rated at a MINIMUM of "10A". I'd also make sure I wasn't testing things near sources of flammable liquids, other electrical equipment, and people or animals and over-hanging tree and bush leaves and branches. I realize this is boring stuff, but sometimes we just forget to think of these things when in "debug" mode.

Excellent video Daniel!!!! Congrats

Awsome mate , I'll follow your suggestion and see how it goes . A very comprehensive explanation, well done .

Great video and helps people find out if they have batteries that can be persuaded to re-charge. Most people just give up and buy a new unit. Particularly liked your comment about the 20v actually being an 18v unit. I have a 20v paint sprayer so I know know I can use my 18v batteries of my other power tools to use the procedure you showed. Many thanks.

Great video really appreciate it it actually does work had a two amp Milwaukee battery with two cells at 1.9 volts each and the other two were at 3.7 v hooked up a 5 amp battery and charged it with in 5 minutes was able to put it on the charger and is accepting a full charge now

Definitely genius!! But that said begs the question(s) how much use now on a single charge can you run that "reconditioned" battery before it runs too low again? Also, what is the voltage threshold where you just dispose of it rather than try to revitalize it?

Thank I will try out and see if it helps

Battery drops below threshold. Can't charge on charger... but can still power drill... Meaning the drill can drop it even more... No protection circuit in tool or pack. That's not a good thing... Really bad design flaw.

Thank you for this fix !! I had my doubts that this would work but I did as the video said and amazingly it worked just as your video said !@great video

Amazing video. Your knowledge and ability to explain is really impressive.

you can get a variable DC supply for $15 and do the same for different batteries/voltages...I've revived a bunch of cellphone batteries(even fancy iphones) the same way

Mark Munro. The DC motor is also a DC generator turn your drill with another drill with the switch held down. That puppy should take a charge.

i watched this video and saved my battery it worked brilliant

Don't burn your house down! 😂 Seriously. Great video. Saving to hard drive. 😁

This works, I had 2-24 v lithium batteries that had 1.6 and 1.5 v left, I did the trick and brought them back to chargeable

Ooooh porter cable brushless 😁 I love my porter cable impact. I bet the new one is going to be fantastic!

Mine worked, and I did it indoors, took about 1.5 minutes.

Amazing video. Just sorted my battery out. Thanks

Good video. Clear and concise.

And that means don't buy porter cable! My makita batteries have lasted me 15 years! I bought the original lxt kit with the mail in rebate for the sawzall!

This really did work, thanks you.

Excellent video! thank you for sharing!

What if my battery reads a full charge when connected to charger, but will not power a tool?

Appearantly no or faulty LVC (low voltage cutoff) on the tool. This is sure to damage the cells if you continue to use it.

It worked for me. Thanks mate, appreciated. 😇👍

Thank you for your help

Keep in mind if you put two of the same batteries nose to nose the positive terminals will be on the reverse side so the wires you put on will need to be crossed instead of being straight.

How does one know if the battery has dendrited? How much life is left in a jump started battery such as that?

How do you determine the positive and negative on those batteries? Are they clearly labeled?

Thank you shall remember this for the future

Thank you for the information. I’ll give this a go. Regards🦘🇦🇺

It works as he said.

Be careful like he said as one of the cells could be dead with a similar voltage to what he showed. This will get the battery to charge, but it will likely have suffered a decent amount of runtime loss after undervolting so severely. It could also go Mt.St Helens. A safer method would be to buy an R/C style balance charger if you have multiple packs like this, open the pack, and charge the cells individually in a terra cotta pot (as they are cheap and insulate well) If it's a larger in parallel pack, things just got more advanced. You would have to disassemble the pack. The drill, and or pack in this video are likely malfunctioning and or of poor design, as an under voltage protection circuit should have literally switched the battery off (so that there would be no voltage at the probes, Methinks it's an issue with the pack itself, this also likely wouldn't prevent an overcharge if input voltage was high enough. Both can result in thermal runaway.) All modern brushless tools also feature over current protection that will automatically trip, just like a breaker if the motor is overwhelmed and calls for more current than is spec, whereas brushed motors typically only have temperature protection.

Can we do this same thing positive to positive and negative to negative with lithium ion ebike batteries ?

How do you tell positive from negative on a round lithium cord?

Would this blow up an air bed which has the build in plug ?

So, if there is any current left in it at all and can run the drill then it's not a short? Just won't charge because it fell too low behind the manufacturer's setting. Wonder why they did that? Was it just a design to sell more batteries or is there some safety issue they had to be compliant with?

You should be using a resistor in series when connecting the batteries like that or at least use one that't more discharged in order to have a lower current draw.

Amazing video, worked perfect for me

Trickle charger from harbor freight does the job to bring up voltage for me on all my tools

Thanks for a fantastic option. This will surely save us lots of cash and minimize unnecessarily throwing away a good battery. Thanks again...Abe Azar

Very good clear instruction

Excellent video and very informative!!

warm greetings. i have a newer battery. no continuity between strap1 and strap2. any advise?

I have seen countless videos on this magical fix. Just because you can fool the charger into charging a defective battery pack does not mean you have brought the bad cell to what I would consider back from the dead. I have tried these tricks on several batteries with little success. When you have one or more cells in these packs fail, they are done holding a normal charge. Try your test on how many screws you can drive with a new battery and compare it to one that you have brought back to life after sitting a few days and see which one wins.

Sir you are mistaken what you are doing is dangerous to say the least the Li-ion cells are 4.2 each charged and should never go below 2.4 volts the cells are series to equal the voltage needed and say 5 series is for a 20 volt then they might parallel another 5 to those for double amperage or wattage . No 2cells are ever the same resistance so they will eventually discharge differently and if the balance gets off to much the charger will shutdown to keep from overcharging some to get to the full charged voltage in the pack, by jump charging you aren't fooling the battery or charger only yourself . If you want to fix the problem go into the case and measure each cell or group and only charge or discharge them to Ballance the pack then if that's what was wrong then you will have many more uses left in them.

What kind of cable did you use??

It totally worked on my 20v lithium batteries . One battery was so dead it didn't turn on my drill at all . Charger was telling me it was damaged . Did what he explained in the video but for 10 minutes instead since it was completely dead . Put it on the battery charger and it said it was hot battery . It was warm after the transfer . But put it on the drill and it ran it this time . Next day once it cooled down I put it on the charger and it started charging the battery this time .

a short circuited 26650 li-ion can be revived? thanks!!!

Excellent video

I had this happen to my RYOBI 40v 6Ah pack. When I plugged it into the RYOBI charger, I got a flashing red light. The pack measured at 27 volts, which is below the charger's magical 30 volt 'bad battery' threshold. But I discovered a way to get it to charge. Just plug the battery in the charger first, THEN plug the charger transformer into the 110v outlet. The green light started flashing (red was off), and it charged fine for me.

This was AWESOME!

excellent works like a charm

Excellent demonstration and idea! Would cable with higher AWG above 12 transfer faster?

Thank you for showing that!

Thanks for the advice. I had one dead 40 volt battery, and now after trying your recovery method I now have 2 dead 40 volt batteries. Any suggestions?

I just saved 80$ on black&decker batteries. Thanks

Maybe I have an older type battery charger...Mine can charge lithium batteries which had no juice in it. And this happened quite frequently when I used them without knowing they were low in juice and dead on the jobs...No issues whatsoever for the charger to charge them up.

Soooo, why do the chargers fail to recognize there is a battery there to charge? I'd like to see a video showing how to modify the charger.

I only joined my 2 batteries for literally like less than 2 minuts and i took the original volatage from both batteries before the 2min and after the 2min on the low voltage battery the volatage was still as it was before however this time the charger actually started charing it... so for less risk don't join them for a long time even if the volage is still low the charger may surprise you and actually start charging them you never know may have same resulst as me (I have worx battery btw and the one that didn't want to charge is a generic worx made by Vanon).

Will it charge every time after that.

What if the voltage from a dead battery pack is at 0 volts? Would this work at all? Going to use a Harbor freight battery to revive.

Just bought the brushless porter cable combo kit drill + impact. The thing is I notices that one of the batteries lasts less than the other one, about 20%. : (

How do you know with one negative and with one positive?

Would you attempt Theo’s with an 82 volt lithium battery that’s only reading 34 volts and a flashing red light on the charger? I left it on the charger over the winter and a flashing red light was showing in spring I purchased a new battery and the charger is working fine.

Say, if you don't have another working Li-ion battery on hand, then would a 2 x 9 volt batteries in series work to revive the dead 18 volt Li-ion battery?

Does this shorten the life of the battery used to revive the bad battery?

Cutting to chase. 48VDC battery pack sitting for about a year will not charge. What voltage would I set my power supply to and do I need to limit the current and if so what limit should I set? After I have the correct numbers what is the length of time I should keep the setup going? Does the battery management board have any effect on this setup?

Could you hook a battery up to a charger this way if you have a battery but no charger it fits on

Thanks, very helpfull video

Kind of Useful solution! Thank u

I have only one 24v can I use a 20vol5 to jump it?

Is that revived pack good for more than 1 use?

Good work .

Thanks for video

hi. what would happen if you used a battery with a higher voltage than the dead battery ?

very usefull for me..👍👍👍

Great video though RTR !! now I know what todo if they stop working on me definitely information I can use...

The same steps can be used for NiCd battery?

Nice and easy to understand !

I'm hoping this will bring my Ingersoll Rand batteries back. Those things are $250!

thank you much

not always the case my battery pack would not charge because it had a bad cell which i replaced now it reads over 20 volts vs 17 volts with the bad cell.

thank you sir

Isn't there some firmware in the battery that makes sure the battery cuts off before it doesn't get down below whatever voltage the manufacture sets it to. I have a Porter Cable drill and driver, and they cut off when I need to charge it. I can still press it, and it turns on for a split second only. But I think it cuts power at 5%.

does anyone know what the charger base low voltage cutoff actually is? also this method is not working when the battery pack gets wet. any suggestions would be great..I have already disassembled the packs, cleaned them meticulously and reassembled . #1 has 19 volts in it but the charger rejects it none the less. any ideas? (PCC601)

What up!! I have a 60v battery 25 ah and reads 67v when fully charged. Let's say I'm riding my scooter and I'm at 58v. Can I use an 80v 6ah battery to boost the 60v 25ah battery?

I had 2 LI-ION 18 volt batteries showing DEFECT last year, didn't take them to the recycle drop off and still have them. Would this method work on them or would it be dangerous??? They have been sitting discharged for a year.

your hand and great video

I have a 18vt Lowe’s , can't get any new batteries. Can I use a 20 v ?

What happens if the voltage output gets lower and lower after each of the transfers?

If the battery pack is really dead, then this is really unsafe. The safest way is to use a lab power supply (constant current/constant voltage) with a low charging current and close temperature monitoring. The way you did it has no current limitation and the charged battery seems to have no protection circuit, considering the fact that it still feeds the drill although it's below the threshold voltage.

Best bet, don't run it that low, safer way to do this, get a hobby grade charger for r/c vehicles, more effective and does a proper trickle charge safely without the need to make new leads.