I'm with everyone else here. I left my battery connected to my leaf blower and the battery was completely dead with the error code flashing on the charger. I used your proceedure and I now have a working battery. Thank You!

another win here. and the razer blades worked perfectly. thanks for keeping this video up

Thanks! Worked for me, but had to do it 3 times at 5-6 seconds each time. The "bad" battery started at 0.5VDC output and would go up 5-7 volts each time I tried this method. After the 3rd try it was at around 23VDC and the charger finally started charging it. Bad battery was a 7.5 AH FWIW. Also, the sparking when jumper attached was a bit scary

I went from 3 working batteries back to 5. Thank you so much! This is an amazing trick.

Worked for mine as well. It sparked at first touch then I held it for 5 seconds. I put it on the charger and it’s now taking a charge. I just inserted the wires directly.

This worked! Thank you for the video! Had one of these sitting brand new in a box for the last five years, so it was about as dead as dead gets.

Son of a gun it worked! I was so skeptical of online fix. Did what he told me, took a full charge, and weed whacked my lawn. So thankful! I appreciate you sharing your knowledge.

Brilliant! I shorted out one of my packs and after replacing the fuse it still wouldn't charge. This simple trick got it back up and running.

Worked for me! My battery was super dead, reading 0.5V with a multimeter. I was able to use a fully charged RYOBI 18Volt from another tool to jump it in 8 sec intervals until the 40V got back to 12.5V, then the charger would recognize it and start charging. Thanks so much. No way I was going to spend $140+ on another battery.

This worked on (2) of my 40v batteries. This saved me almost $300.

I've tried on older craftsman battery without luck and then just tried with larger 40v Dewalt. It worked this time but be careful to only do for a few seconds. I had smaller gauge wires connected like this guy and seen wires start to droop after about 8 seconds so I could tell heating up and they were very warm.

This worked perfectly. My one 40 v DCB404 wouldnt charge. Fortunately I had another. Jumped the good to the bad and it worked. Saved me a fortune, these batteries are so pricy your better off trashing the tool the are used on. Thanks Joe!!

This works because the battery cells (li-ion) have a voltage curve (more like plateau) meaning once the battery hits a certain percent discharge, the voltage rapidly drops. This jump-start pushes enough amperage into the battery to put the battery back into a proper voltage range the charger will recognize. I wound up using an RC battery charger to do the same thing (opened the battery and charged half at a time to 60%) wound up running the battery from 6v to 37 in minutes, then the normal charger recognized it.

bought a brand new 40v chain saw that was never used on Ebay, still had a wire tie on saw trigger lock, was disappointed the battery would not charge and indicating a fault, other battery i had was ok in the charger. the new battery was flat as in 0v, used small finnish nails to hook up alligator jumpers, touched fo 5 secs, with a good spark, put in charger, still fault. Did this again for 5 sec and put in charger and away it went, woohoo, This brand new battery was charging probably for its second time ever, the first was the factory charge. Kind of pissed at dewalt for abandoning the 40v line

This totally worked. The 40v system is discontinued and thought I was going to have to toss my blower and string trimmer. I have 2 of these batteries and unfortunately both were “dead”. So I didn’t have a good battery to do this with. I connected one to a 6s 22v rc lipo battery for just a couple seconds and I couldn’t believe it when I put it back in the charger and now it’s charging!!!

Worked for me!! Thank you

Update: A basic description of why this works. For whatever reason the battery voltage of the target battery has dropped too low to be recognized by the OEM charger. When you jump the battery it raises the voltage and the OEM charger can recognize and charge it. My success rate since this video is about 7 out 10 restored Lithium batteries for various tools using the jump method.

Wow! Worked great! Glad I found this! I was getting ready to trash 2 batteries!🤪🙄

Tried it, seemed simple to do, with no equipment like meters etc. It worked great. Only had it connected to a charged battery for less than a minute. Awesome.

OMG thanks thanks thanks it really works Thanks sir

One quick spark and it's charging normally now. :-) Actually, the blades work quite well.

Worked perfectly! Thanks for sharing!

Thank you. Sir.

Don’t have another 40v. Used couple 20v. I did

Didn’t work for me

I have several of these new in a box - no clue what to do with them