Flexvolt Battery Fault Diagnosis and Repair

This video shows how to take apart a flexvolt battery and repair it.
The flexvolt battery is a dual voltage innovation from dewalt it is suitable for 18v and 54v tools 20v and 60v in USA. The flexvolt uses samsung 21700 cells as opposed to the 18650 cells used by the XR. This video shows a burned connection and the repair I carried out to a battery that was no longer functioning as intended it would still power XR 18v tools but not 54v and would not charge. I also had to clean the terminals to make it work. I show how you can sometimes repair these by relatively low cost means. Can You repair your 54v/60v flexvolt battery if its not charging ? If I can you can
#repair #dewalt #powertools

[@doctorlefthandthread]

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[@HossamElramy3]

I love how you showed everything that didn’t work except what actually worked lol

[@PULSARGT]

Disclaimer, these findings are my own and took all the safety precautions, if you don't have the knowledge and experience working with these batteries, you should not attempt it, do it at your own Risk. I figured out what the problem is, the problem is within the battery itself and it can be 1 of 4 possible issues. The battery consists of 15 cells, each 5 are grouped together to provide 20 volts, when combined together it results of 20+20+20=60 Volts, if one of these groups is faulty, the 20 volt tools will continue to work since each group provides 20 volts and they are all setup in a parallel configuration, may not last long but the 20 volt tools will work. When the battery is put into 60 volts configuration, by sliding/pushing the side black pins all the way to the back as well as you have to actually short C1 and C3 pins by means of a jumper wire, you will get 60 Volts across B+ and B- when fully charged if all 15 cells are good. Below are the steps you can do to determine what the issue is. 1- take apart the battery and check for blown fuseable links, each side of the battery has 3 major connection from the BMS (Battery Management System) to the actual batteries, one link is skinnier than the rest and may blow, and most likely it blew due to faulty cell (9ah & 12ah use 21700 cell while 6ah use 18650). 2- If a given cell is bad, the best way is to isolate and determine the one that is bad and replace it, to do so, push and hold the slider all the way (I shoved a piece of plastic to hold it in place while I am doing the testing), this will separate the 3 groups; then measure each group and determine which one has the lowest voltage (you many have bad cells across more than one group), you will find at least one cell that is below 3.6 volts while the rest should be above 3.8 volts. 3- check the spot welds on the batteries, use a tiny screw driver to try and shake them, I got one cell where the spot welds weren't making contacts (this is very rare, option 1 or 2 are the most common). 4- BMS is bad, Battery Management system. 5- You are welcome :)

[@doctorlefthandthread]

Thanks for the advice

[@xPPBx]

I have brought 3 9ah within the year 2 have packed up on me… thinking about swapping to Milwaukee

[@simonclark8290]

Really good to see that some faults are more straightforward. I have a question which you may be able to answer. I've just received a new 54V flex tool from DW but the battery code is 2022-47 and it's August 2024. If this battery goes faulty how do I prove it's not 2 years old and should anyone accept a new tool with such an old date stamp on a battery?

[@doctorlefthandthread]

You need your receipt to prove it you can register a battery when it's new as well

[@MrKevin920]

If you want to see the 54v volt on meter you have to short C1 and C2 together and push the Bar in then you can see the other voltage

[@doctorlefthandthread]

Thanks for the advice

[@MrKevin920]

@@doctorlefthandthread no problem

[@adriancullen3293]

I had the same problem with a 6ah 54 v battery, charger weld start charging and stop. I put the battery on a DeWalt torch and left on until battery completely flat, it then charged to full capacity

[@doctorlefthandthread]

That does work I have done a video on that fix too

[@rishisonoo7997]

Good video but it would have been better if you showed how to remove the top and what exactly you sanded.

[@doctorlefthandthread]

Thanks for the advice

[@ianhelsbyservices]

I've tried to dismantle a 9Ahr but the top is stuck on. It seems to be pulling at the side PCBs so will have to desolder them to remove the top.

[@team5824]

My 6ah flexvolt displays only one led and when connected to charger both lights come on after about 10 seconds but battery is flat...... Any ideas thanks

[@doctorlefthandthread]

Take off the sides look for broken connections

[@AlbertMartinez-vb9qo]

Would be nice to see what you’re doing there

[@doctorlefthandthread]

Sorry this video is one of my older battery ones and maybe not as well made as it should

[@sl12229]

What is the name of the welder??

[@ChiodiConstructions]

Why doesn't anyone explain how to remove the Top, Mine is stuck and is lifting the 56v switch mechanism!

[@doctorlefthandthread]

If you have the 4 screws out that hold the top on you have to pry with a screwdriver they are stuck on

[@ChiodiConstructions]

@@doctorlefthandthread Yeah I got it off in the end, its funny the newer models don't have any stickiness and are easier!

[@jamesdrennan890]

I have one of these same problem. Haven’t opened yet but not far away from you by the sound of your accent 🤔

[@doctorlefthandthread]

I got lucky with this one saw what was wrong right away. The standard batteries are more straightforward to work at than the flexvolt. Yeah I am in Tyrone.

[@emmettturner9452]

There’s a video of MrSubaru responding to VCG Construction regarding FlexVolt batteries and MrSubaru shows that the voltage is supposed to drop if you just hit the 60v switch without signaling through the middle terminal. Basically, every FlexVolt battery has two switches: Electronic and physical. You need to do both to get 60v.

[@doctorlefthandthread]

Yes

[@bradleyadams8397]

Mine seems too be a little diode or small tf or B fuse in the f1 line anyway how too change or replace it or even were too get such tiny little things I got 12ah flexvolt battery

[@doctorlefthandthread]

I honestly don't know they are the most complicated battery on the market due to the dual voltage set up I got lucky with the one I had

[@dannpurvis]

Love the accent…just wished I could understand it 😅

[@doctorlefthandthread]

Thanks watch my livestreams on Sunday night maybe you will get used to it and understood

[@mandamados]

tha connection is working like fuse and the nickel strip is narrow in that place. In many photos in the internet you can confirm this.

[@doctorlefthandthread]

Thanks for the info and fear not because the strip I use is only 0.1mm so it will burn out in case of overload quite easily

[@kevbarry7453]

Where can I get the little spot welder. It looks so neat. Can you post a link thanks.

[@doctorlefthandthread]

Here you are it's on ebay www.ebay.co.uk/itm/394275666040?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=yFg8j8t5T3q&sssrc=2349624&ssuid=cjPn_ZfdQLW&var=&widget_ver=artemis&media=COPY

[@KuwaharaBMXRider]

I've given up on Dewalt due to their shockingly bad reliability of their flexvolt batteries. I have a living to make I can't be messing about with batteries. Ive replaced my entire tool set with the makita 40v battery system. The flex volt battery isn't fit for use

[@doctorlefthandthread]

I would tend to agree They're too complex too much to go wrong

[@KuwaharaBMXRider]

@@doctorlefthandthread they need to go back to the drawing board and design a system using the pouch type batteries

[@doctorlefthandthread]

@@KuwaharaBMXRider I think they gotta put too many protective measures in them due to the volatile nature of lithium-ion they probably err on the side of caution.

[@KuwaharaBMXRider]

@@doctorlefthandthread they seem to manage just fine in mobile phones

[@doctorlefthandthread]

@@KuwaharaBMXRider good point

[@kenroper68]

Hi what size bit to remove screws please

[@doctorlefthandthread]

TX10 security torx

[@kenroper68]

Thank you great video

[@SrenSkaanning]

Thank you for the video. Very helpful! What kind of nickel plate should I buy to do this on one of my own batterys? I wont risk anything in case of over load.

[@doctorlefthandthread]

I buy 0.1mm nickel strip in case of overload it will burn through like a fuse and disconnect so very safe. The 0.1mm strip is easy to weld with a low power welder too.

[@davideloewen]

​@@doctorlefthandthread i have the same issue with a battery, what amperage does it take to overload? I was thinking about putting an actual fuse in to repair mine, but I was unsure what amperage I should use.

[@doctorlefthandthread]

@@davideloewen I use fine nickel strip 0.1mm I know that it will definitely burn through before if anything goes wrong. It happened to 2 of my repaired batteries when I accidentally shorted them. It kept me safe and both batteries were easily repaired again.

[@davideloewen]

@@doctorlefthandthread thanks! I might have to try that. I don't have a spot welder though, just a soldering iron... I did a little reading, and it looks like the Samsung 18650 cells used in these have a maximum safe discharge of around 20 amps. (My battery is a 5s 2p) so if I understand this correctly the 2 parallel battery circuits would have a maximum safe discharge of around 40 amps. So long as it's set up to fry at around say, 30 amps, it should be fine... I think... Feel free to correct me I'd I am wrong I'm kind of a novice when it comes to this kind of stuff, but I'm trying to learn, and I really dont want to start a lithium fire.

[@doctorlefthandthread]

@@davideloewen I am no expert either but I know the strips burn out quick if the battery is shorted because I have done it accidentally before. I don't solder directly on to the cells although there are plenty of people who do. My fear is solder run to cause a cross connection on the positive end of the cells. Lithium fires do not seem fun so be careful.

[@tommarkm8058]

You can’t check the cells without disconnecting them all can you?

[@doctorlefthandthread]

It's tricky on flexvolt if you can check the voltage of all but one then check the overall voltage by connecting c1 and c2 terminals then pushing in the 54v slider you can work it out. Flexvolt are awkward as hell

[@alonsonevarez2770]

What i did, i drained all the charge of the battery(with a 20 volt weed eater) after that, it seems to be charging good.

[@doctorlefthandthread]

That's awesome thanks

[@gositdown.3800]

Can't help becoming skeptical of the fix authenticity when the video skips the pertinent repair work.

[@doctorlefthandthread]

Check out my channel all I can say is I don't fake anything I have a tremendous amount of battery videos decide for yourself youtube.com/@doctorlefthandthread

[@raulmarin8704]

That battery is not original dewalt my friend

[@doctorlefthandthread]

Can I ask why you say that?

[@PULSARGT]

Yes it is, Dewalt made 3 variants, this is the first one

[@RikoRey92]

My flexvolt battery is not working on Flexvolt tools but it works on 20v tools. Do you know what could be wrong?m

[@doctorlefthandthread]

That's common I haven't come up with a fix for it yet

[@RikoRey92]

@@doctorlefthandthread thx for the quick response, will you ever make s video for that issue?

[@doctorlefthandthread]

@@RikoRey92 if I can figure out why it happens I certainly will