[KwartzLab] battery pack rebuild: results!
digitalfalcon at rogers.com
Thu Sep 22 22:11:56 EDT 2011
Thanks for the results. As for running the drill directly from the charger, I'm not sure I'd recommend it. The drill draws a ton of current, likely more than the charger can handle.
Sent from my iPod
On Sep 22, 2011, at 9:59 PM, Andrew Netherton <andrewnetherton at gmail.com> wrote:
> It's been a good long while, and I thought I'd post a follow-up.
> I recently disassembled a heavy lumber structure in my garage that was
> mostly screwed together. Very high torque to get some of those screws
> out, it really gave my cordless drill a run for its money (and in a
> few cases, stopped it cold). I even managed to cycle both packs
> through some quick charge cycles.
> I managed to get most of the structure apart before one battery pack
> suddenly stopped working. Taking it apart, I noticed that it was the
> pack that I had soldered the battery leads directly on to the adjacent
> battery. One such junction had failed, but some of the wiring that
> was in the pack originally had also burned through the insulation. So
> that pack is toast.
> I continued with the other pack, but within an hour of burning out the
> first one, the second one stopped working as well. This one was the
> pack where I soldered the tabs of the battery together (the
> replacement cells I had purchased had spot welded tabs top and
> bottom). I did that figuring it might result in a stronger solder
> joint, and would prevent any heat damage to the battery cell itself.
> Well, in this pack there wasn't any burnt wires, but the pack quite
> readily fell apart - many of the solder joints had failed. Whether
> the high current actually melted some I can't say.
> So my conclusions are that rebuilding your own cordless drill pack is
> entirely possible, and works well for everyday tasks. Once you start
> getting to tasks that really task the drill and put a serious draw on
> the battery, however, a pack rebuild with soldered connections likely
> won't cut it. At that point it would be necessary to use a capacitive
> spot welder or equivalent to get a permanent connection that is both
> mechanically and electrically sound.
> I don't think I'm going to rebuild these packs again. Instead I'm
> going to disassemble the pack charger, and hook up the DC output
> directly to the drill and see if I can run it as a corded drill. I'm
> hoping I'll get close to full power that way, instead of piddling by
> with a wall wart or having to go full-bore with a PC power supply.
> I'll be dependent on mains power, but will have a much lighter
> (although now imbalanced) drill to use. If I ever come across a
> heavy-duty 12V battery, I might see if I can find a middle ground -
> tethered to a large, powerful, non-hand-held battery, but still
> portable enough to take anywhere.
> On Wed, Jan 26, 2011 at 8:07 AM, Andrew Netherton
> <andrewnetherton at gmail.com> wrote:
>> Last night at TON I managed to rebuild one of my two cordless drill
>> battery packs. It was a bit slow going at first, as I had to climb
>> the learning curve first, but eventually did get a pack made with the
>> new cells I had. The cells were all soldered together, which worked
>> well enough, despite not being especially pretty. (Next time I'd
>> probably just weld tab-to-tab, but that will be pack #2.) After I got
>> home, I got out the charger and popped in the rebuilt pack. The
>> "quick charge" light came on, which was a good sign.
>> As of this morning, the pack was registering as fully charged, and the
>> drill once again turns! WOO!! So I'm calling the rebuild process a
>> success, and will now just have to wait and see what kind of life I'll
>> get out of the pack.
>> A big thanks to all who helped me with the rebuild, especially Mark
>> for his mad soldering skills. :)
>> I've already got some process improvements in mind for the next pack,
>> but I'm not sure when I'll get out to do that one (my wife's water
>> just broke this morning, so I'm home for two weeks). Once it's
>> complete and have the process a bit more refined, we can call a meetup
>> for rebuilding the DeWalt, and anyone else's packs that may want to
>> try their hand at it. (And if anyone wants to whip up a capacitive
>> discharge spot welder in the meantime, PLEASE DO!!)
>> Thanks again, KWartzlab. I'm seriously stoked at how well this worked!
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