unused Dewalt A123 26650 cells from 2007....your thoughts?

[ElementX]

Your thoughts on how unused Dewalt A123 26650 cells from 2007 manufacture date will respond in 2018?

Roughly 8-9 years ago, I bought some Dewalt 28v lithium packs for some projects that unfortunately had to take a backseat over the years. Also bought chargers and some 28v flashlights to chop up for their connectors. On top of that I also bought the kfong circuit boards and a Lyen edition controller. I know this is all old tech now, but thought it might be interesting nonetheless.

Pulled most of my old project stuff out of the garage recently and found most of the Dewalt gear. Gonna start tearing apart some of the packs to see what the cell voltages look like.

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[999zip999]

Are they all new like the ones in the package or do you have a mixed group new and used ?
First check the packs voltages labeled a b c or one two three and or just write on them. When you find a low one open it up and see what the voltage of each parallel set is. Share with us. Best if above 2.8volt or above. I think pack 22volt after sitting is golden or grade A. What you got ? It all about the numbers.
My pouch A123 are 2008 and installed 2012.
I have 1,195 cycles 20,000 miles. Still use at 80amps . Use to balance charge no bms burned up 4 balance chargers. Screw that just bluk charge and self monitor.. Maybe good for 4 more years.

 

[999zip999]

Check them all before charging make a list on a piece of paper be so easy to keep track. As you are starting fresh in from the beginning one or two weeks and you have all those things all mixed up.

 

[ElementX]

I think I have a total of (12) 28v packs, but I can't find the 12th one lol.

6 packs were opened back around 2010 and never used to power my ebikes. I bought the 28V Dewalt circular saw and used it very sparingly over the years. I did use them with the flashlight attachments on fishing trips though. Only reason I opened that many blister packs back then was to physically fit them to my project bikes.

I needed to use the saw recently, and as you would imagine, those original 6 packs wouldn't charge. I opened a new pack (pack#7) and to my surprise it powered the saw out of the box. I opened another new pack (pack#8) and it was dead/wouldn't charge. Next pack (pack#9) worked out of the box so I'm down to 3 new/sealed packs.

Today I pulled apart one of the older packs and measured the cells.
Of the 8 cells,
- 2 cells were completely dead with 0v
- 1 cell was ~2.67v
- 5 cells were ~3.30v-3.33v

I'll tear down the other packs in the next few days, cut the cells apart, and get them sorted as you suggested. Since I already have the kfong boards on hand, I may as well figure out what cells are still good and use them to rebuild the dewalt packs.

 

[999zip999]

From my experience a lot of tool pass lose to death that are easily cut away and then start from there did BMS brain on a couple early parallel cells. These dead cells are paralytic parasites in the rain off the other parts. I guess maybe I guess right. The other cells that are 2.56 can be brought up to a respectable 2.8.. The dead stills cut them off with a ceramic sitters or a Dremel be careful not to touch the other cell the good cell.

 

[999zip999]

What was the pack voltage of number 7 and number 8 before you open it up ? If your right is down on a piece of paper it's so easy for you to keep track on the computer not very good in your mind forget it.
So what's the layout of the batteries S&P ?

 

[e-beach]

My thought is to put the ones you can on the charger and see if they charge. If they do, put them on a tool and see how long they last. If they don't charge, cut the cells apart and charge them and test the cells individually on a imax B6 or similar charger to see how long they last.

My expectations are that most of them have aged too long and should be retired. Much better batteries are being made today anyway.

 

[ElementX]

What was the path voltage of number 7 and number 8 before you open it up ? If your right is down on a piece of paper it's so easy for you to keep track on the computer not very good in your mind forget it.
So what's the layout of the batteries S&P ?

I haven't had a chance to open all the other packs yet, but I just checked the volts on packs 7 and 8.

Pack#7 - 28.01v before charging, 30v after charging on Dewalt charger.
Pack#8 - 19.55v....so I'm guessing 2 dead cells here too

 

[John in CR]

Once you take the string of cells out of the plastic case and remove the electronics board, I would suggest cutting only the dead cells apart. You at least triple the work and can only do harm to cells by removing factory series connections between good cells.

 

[999zip999]

I check a few and then charge to hall well one or two charge to see if the bms will not over charge a cell over 3.7v. That before you decide to charge all packs. The BMS can be connected to that first Parallel Group and be parasitic just to two cells if you put it on the charger and for some reason the BMS doesn't cut off property and just charges some of your cells will be over 4 volts making them no good. I was hoping you can use them as individual 28 volt packs and put two in series and as many as you need in parallel still keeping them in the DeWalt packs for a low wattage use around town daily driver. I wouldn't mess with the zero voltage cells just cut them off with a dremel maybe put a popsicle stick or some Thin bamboo underneath so you don't Nick the cell. Don't let them knuckle tabs of a positive cell touch the can of the cell you're working on.

 

[ElementX]

Thanks for your help guys!

I tried charging some of the dead cells, but they were a waste of time as you said. Voltage on those cells dropped back down to under 0.5v within a few hours.

Since I already have the kfong boards and lots of Dewalt chargers, I'm going to just replace the dead cells and rebuild the packs in their Dewalt cases. I haven't decided if I'm going to try to solder them because I'm not sure if there will be enough space in the case to account for the added thickness of solder on both sides. I'll have to test one and see before I try to rig up a spot welder.

 

[999zip999]

Do the dead cells live on one end of the pack or in the middle to ?

 

[ElementX]

I'll be opening up all the packs again sometime this week, but from what I remember, it was a mixed bag.

The most common dead cell was the one at the end of the negative side.
2nd most common dead cell was the next to last cell on the positive side.
There were a few packs with a dead cell in the middle of the string, in addition to one of the above.

 

[ElementX]

I pulled out the kfong dewalt interface board to test today. It powered up a pack and I was able to measure 29v. Then I plugged it into a 24v ecrazyman controller and it immediately shut down the BMS.