Battery problem...

[alexwang32]

Finally had one of my Dewalt batteries die on me, in the middle of a job.

I wouldn't post this here without having tried everything I can think of and find on the net, which includes cleaning the contacts with alcohol, checking voltage, switching chargers etc.

The charger would charge the battery for a seconds normally, then the light stops flashing, as if it doesn't recognize the battery. Same phenomenon every time.

It appears that the cells are equal, no abnormal voltage in any of them, the fact that it just refuses to charge all of a sudden really bewilders, I always take good care of the batteries by not using up all of its juice... I have batteries from 5 years ago which, although have declined in capacity, can still take a charge.

The battery I'm having issues with is 2 years old, with their limited warranty on these things I'm guessing filing a claim won't help.

By any chance anyone here experienced the same problem and succeeded in fixing it in the end?

Thanks...

 

[GeoBruin]

It sounds like you've measured the voltage across each cell individually but it seems like that would require breaking the spot welds to accomplish. Have you done that or figured out some other way around it? Unfortunately, I would expect that to be the issue - a single bad cell in the bunch. I've managed to source the exact same cells needed for a friend's milwaukee pack and he is currently undergoing "surgery" to swap out the bad cell. In his case it was a pack he dug out of the dumpster at work so warranty wasn't an option.

Good luck!

 

[alexwang32]

Hi Geo, thanks for replying.

Well my idea of testing out the voltage of individual cells is by measuring between the C1, C2, C3, C4 and B-. So in my case I have a 20V battery, the total voltage across B+ and B- is 18.5V, if the first measures 3.7V, second 7.4V, third 11.1V and so on, the cell should probably then be equalized as the increments are the same.

I saw some videos on youtube where people disassemble a battery pack and swap out the bad one, very remarkable work, but not something I can indulge in at the moment. If I do get to it someday maybe I'll ask you for some suggestions.

 

[American Locomotive]

What's interesting is that 3.7v per cell shouldn't be a dead battery with lithium. 3.7v is the nominal voltage rating for those cells, so they should still have like 30-40% of their capacity left. Do you have voltage at the battery's main contacts?

 

[alexwang32]

What's interesting is that 3.7v per cell shouldn't be a dead battery with lithium. 3.7v is the nominal voltage rating for those cells, so they should still have like 30-40% of their capacity left. Do you have voltage at the battery's main contacts?

Yeah the battery definitely has juice in it, it can even still power my impact driver with no problem, though I'll refrain from using it until I can get it to recharge. It shows two bars, which according to DEWALT means it has more than 50% of it's capacity left, total voltage is now 18.2V.

I have no idea what the charger picked up from the battery that it makes it consider it to be dead... As far as I can tell this battery doesn't differ from other ones at all.

 

[mrvm]

Try a different charger. Sometimes it worked for me.

 

[Robbie B]

Watch this video and try this. It helped my batteries.