A123 M1 Cells from Dewalt 36v packs
 

There hasn't been much information here (if any) about actual Dewalt 36v packs being disassembled for the cells, so here is (another) new thread. I got my first pack in today, factory sealed in plastic packaging. Since I had bought a security bit set, I was able to remove the star-pattern security screws without any trouble, so that the plastic case halves could be removed. Then I pried the cells out, and measured the voltage of each cell. All cells are at either 3.31v or 3.30v (good balance), except for one cell, which is at 1.11v. This is quite strange, considering that I am the first person to touch this battery since it left the Dewalt factory. I will charge this cell up to see if it can be revived, but I will be keeping tabs on it from now on.

I'm not yet sure if this is of any relevance, but the date code on the cells appears to be February 2006, as the cells have "FB06****" on them.

Another Dewalt 36v pack is on its way to me. This one cost $100 shipped, while the one I already have cost $101 shipped (both from Ebay). Hopefully that pack will not have a low cell, and it will be interesting to see if it does because that pack is also in the factory packaging.

That kind of sucks about the one cell. Keep us informed.

I brought the cell up, adding 548mah at 500ma starting and changed to 1amp halfway through. The resting voltage 5mins afterwards was 3.317v. We'll see if it holds.

That is odd.

Do you plan on removing the stock bus bars and soldering directly?

$101 shipped for 10 isn't that bad as retail is around $155 for 10.
What does it take to disassemble one of these packs? Are the cells soldered together?

I think I will solder to the tabs. Right now I have battery bars that have a hole in the center (so the vent isn't covered up), and I also have two different types of copper braid. For side by side, I think I'll use the bars, and for inline, I'll use the braid.

Retail is actually $16.50 for these cells.
It isn't hard to take them apart, but it makes it a lot easier to use a Torx driver bit to take the screws out (Harbor Freight has a 33pc. security bit set for $3). The cells are connected by metal strips through 4 weld joints.

What about those solderless power tubes? I hear they work well, but I guess there's no dummy cell for odd number packs yet...

Too expensive for me :).

really? i could have sworn i saw them selling dummies

They could be out now. The last I looked they weren't...

MM: Too expensive? Even with your "connections" at your work?

We can't get all brands of items, especially since Hobby People is a big hobby shop (23 stores, and a website).

I just got another Solderless power tube today from modelelectronicscorp.com
Pete was originally able to sell these cells individually for $13.50 each but A123 increased the price. He now sells them for $15.50 each. I guess I should have bought more sooner :007: The nice thing about Pete's cells is they have never seen solder and they do not have tabs. Money is definetly a factor but buying Dewalt packs have several caviats that could possibly out weigh the initial cost savings (dealing with possible crapy ebay sellers, receiving damaged or bad packs/cells, extra time spent tearing down and building a pack from scratch). I guess I probably sound lazy but I like a good product and would rather spend a few extra bucks to get it done right than to mess something up.

Pete does have a phantom cell solution but He is waiting for the first order to arrive. I'll convert my 2 cell pack to a 3 cell pack as soon as I can.

My current 6 cell setup gets a flat 15 min on the short track. Thats only charged to around 85-90% so I'm hoping 7 cells will squeek out an extra minute for those 15 min mains.

Since the SPT's don't have balancing wires, I'll have to disassemble the packs to balance the cells individualy. I'm using the LipoDapter so the cells never reach full charge so I'm thinking I'll probably balance them every 15-20 cycles.

What others have done with their SPTs is they have cut holes in the plastic tube and soldered wires onto the cells so that they could balance the pack easily. The only problem with this is that the cell cases are aluminum, so you need aluminum flux to solder to them.

After more than a month, I now have two separate packs using A123 cells. The first I built is a 3s2p and a 2s2p in series (5s2p). This pack was made using a technique I developed. The basis for this technique is soldering the cells side by side, but then putting them into a stick configuration. Basically, it's 5 groups of 2 cells in parallel. And with this method, I was able to keep the vents open, in the case that the cells need to vent. The copper braid I used to connect the cells together is soldered onto the metal tabs that came welded onto the cells.

Just yesterday I finished my two 2s2p brick packs. These are squares, 2 x 2. I soldered them together the same way as with the first packs, but didn't put them into a stick form.

I'll try to get some pics soon. Unfortunately I didn't document the buildup on the stick packs, so you won't be able to see how they were assembled.

I noticed that another manufacture (either Bosch or Hitachi) actually monitors individual cells on the charger for their Li-ion batteries.

Not sure about the DeWalt packs, but the emoli cells in the Milwaulkee packs monitor each cell as well...

I'm pretty sure the Dewalt packs do too. There's a whole module that does all of the protection for the cells.

How hard to do you suppose it would be to remove the battery bars from the cells. You guys have me really curious about these A123s. I just got a 7XL to run in a buggy conversion that I am doing and lipo has me kind of worried because racing can get kind of rough. I'm even considering going back to nimh for running at the track.

I want to use the cells in power tubes. One in a 3S2P configuration and the other in a 2S2P configuration for a total of 5S. I think that my Mamba Max ESC can handle that and the A123s should be much safer than lipo too. I figure I could have a complete set for about $140, if I use cells from a dewalt pack.

these cells look like a123's?

If you just pull (or "rip") the tabs off, the tabs will take small chunks of the aluminum from the can of the cell (where the welds are). To prevent this you need to grind the tabs off around the welds, and then grind down the welds so that they are flush with the positive/negative terminal. It's a bit of work, but it's a lot cheaper than paying $20+/cell!

They are.

I understand that they look like A123 cells. I've never seen an A123 cell. At least I don't think I have. From what I gather, they are identical in size to a C cell. Is that right?

I haven't compared them to a C-size cell, but here are the dimensions on the A123 cells:
26x65mm (1.02x2.56")

Thanks, that is about the size of a C cell.

Thats actually a good bit longer.