Dewalt 20v Battery Not Fully Charging

[bad_idea]

I tried Google, but it seems most people have issue with running the batteries too far down and then they won't take a charge. That is not my issue. I have (2) 5ah batteries that charge to two bars and then the charger says they are done. Anyone know how to fix this issue? Thanks.

 

[cgrutt]

Guessing there are one or more weak/dead cells in pack. Does charger fully charge other packs? Can take the pack apart and measure voltages of the individual cells.

 

[LB-1911]

DeWalt battery won’t charge past 2 bars?


It might be the case of a loose connection in the outlet or a loose battery. The battery will blink red light if it’s not inserted properly and won’t charge past 1 or 2 bars. Also, it can be a faulty charger or outlet and so replace them.

Source & full text @

6 Reasons Why Your DeWalt Battery Won’t Charge Past 2 Bars

DeWalt battery won’t charge past 2 bars is a problem that happens if the battery’s too cold or hot. Also, it can be a loose connection. Find out more here.

powertoolinstitute.net

 

[bad_idea]

I found that article in my search. Those are not my issue. I checked those items.

 

[darkzero]

I had 3 (well 4) of my M18 batteries have this issue just this past year, two of them being 9 yrs old & never had a problem until now. But then again I negelected to keep them in rotation/use & happened during cold weather (well cold for where I live).

Anyways, they wouldn't fully charge either, would charge to 3 of 4 bars then the charger will say fully charged. On all 3 packs one bank of cells were low. I charged those banks individually & brought the voltage up to meet the other banks. All 3 of those packs are working perfectly fine now.

The 4th one I mentioned I suspect had the same issue. But it was still under warranty, just in case it did have bad cells & being an expensive 8ahr 21700 pack I sent it in for warranty..... MW replaced it.

 

[bad_idea]

I do not have a charger like that. Can you recommend one capable of fixing this issue with consideration for very limited use after fixing this issue?

 

[darkzero]

You don't need a charger like mine. That's a charger for RC car batteries that I've had for a very a long time. Do you have any kind of li-ion charger that will charge individual cells, like most commonly an 18650 charger? They'll work, just will take longer to charge.

Just need to hook up the positive to positive & negative to negative (charger to bank). Make a note of what voltage all the other banks are at. Monitor the voltage of the low bank being charged & stop charging when it gets to about the same voltage as the other banks. Then put the pack back on the Dewalt charger & charge as normal. Assuming your issue is a low bank.

 

[darkzero]

Can also do it with bench power supply but most people wouldn't have one unless they mess around with electronics a lot.

There's also the crude way of doing it by jumping with another battery pack or cell(s) to bring up the volatge. I personally wouldn't do it that way but if your careful & know what you're doing it can be successful. But can also have a very bad day if you're not careful. Should be plenty of videos on youtube.

 

[bad_idea]

Gotcha. I am fairly clueless when it comes to electronics. Need to use small words and type slowly. I do have a couple desktop computer power supplies. I am gathering from my context clues that I need to apply a voltage until the voltage of the cells comes up to match the other cells. What voltage am I looking for?

Off to YouTube to research the topic.

 

[kbeefy]

Glad this thread came up, one of my 12v batteries stopped charging past 1 bar.
I think I'll take it apart this week and see what it looks like, thanks!

 

[kbeefy]

IIRC they need to be around 3v per cell. Charge voltage is about 3.6-3.7v

The interwebs has the right numbers, if you get yours close the tool charger should be able to finish it.

 

[darkzero]

Gotcha. I am fairly clueless when it comes to electronics. Need to use small words and type slowly. I do have a couple desktop computer power supplies. I am gathering from my context clues that I need to apply a voltage until the voltage of the cells comes up to match the other cells. What voltage am I looking for?

Off to YouTube to research the topic.

I wouldn't mind taking the time to do that but lots of videos on youtube that can show much better than I can explain in words. Here's a couple that I've found just quickly searching. I'm sure there may be better or shorter to the point videos.

The second video don't let all fancy equipment deter you, just try to get an understanding of what the problem & the goal is. I only skimmed through these videos so hopefly they are explaining in enough detail.

 

[cgrutt]

IIRC they need to be around 3v per cell. Charge voltage is about 3.6-3.7v

The interwebs has the right numbers, if you get yours close the tool charger should be able to finish it.

Generally nominal voltage is 3.6v or 3.7v per cell. Min voltage around 3.0v or 3.1v. Max charge up to about 4.2v.

 

[kbeefy]

Glad this thread came up, one of my 12v batteries stopped charging past 1 bar.
I think I'll take it apart this week and see what it looks like, thanks!

A week, 3 months... close enough.

Finally pulled apart this 12v battery to try and figure out whats wrong with it.
It will only charge for a few seconds then shows fully charged. When I put it in a tool it only works for a second before hitting the voltage cuttoff. I tried jumping it with another pack and didn't have any luck.



I checked and it looks like one cell is acting like a dead short. Measured 0.0v. The entire pack was reading 8.4v.
I don't have a lithium charger for single cells, but I found this cheappy charger for 18650 cells for a flashlight.
It read voltage when plugged in and no cell in it, so I hoped it was 'dumb' enough to charge a dead cell. Nope.
I used jumper leads and once hoocked tot he battery pack it dropped to zero volts.

I used the charger, not plugged in, as a holder for a charged cell and hooked my jumper leads to it for a while. After an hour or so the dead cell was reading 2.5v. I then plugged the charger in.... I was in a hurry so I didn't get an extension cord but instead used this handy work bench with an outlet built into it...



I let it charge for a few hours, then reassembled everything. The battery guage read full, so I put it on the actual tool charger.

It seems to have charged up and has been working for 30-40 minutes of use. I'm calling it a win, no clue why one cell went flat.

 

[IRQVET]

Ran into the same issue. Battery is 19 months old. Emailed Dewalt, explained the issue, got an email they are sending me a new battery. Super easy process, I was kinda shocked. Though I'd have to jump through more hoops.

Happy to see a corporation looking out for the little guy. I'm a DIY'er, not making a living with this stuff.