|Contributed by: Speed Munkey | Published: March 2005 | Views: 49963 | Email this Article
of the most frequently asked questions I get is How do you
assemble your own battery packs? The answer is a rather lengthy
one, but not difficult at all once you are comfortable with the
steps involved. The biggest key to doing this right is to have all
of your materials assembled and ready to go when you need them.
Extra special thanks go to John at Team Scream for his very kind
donation of the killer cells and build kit I used here.
6-cell race pack
Assemble the cells
and go racing
Working on a mat can save the table from being ruined by hot
solder and sticky flux. Here, I'm working on a desktop mat
that was purchased at Staples. It's a rubber mat that is both
non skid and hard to melt.
few words on shop safety before we begin
Soldering is a very
toxic hobby. The fumes and, in some cases, the lead in the
solder can really mess with your health. When soldering, I
always have a fan blowing across my work area and I wear disposable
vinyl gloves. You can't race from a hospital bed, so do the
right thing. Eye protection is also a good idea, because you
also can't race if you are blind from being splashed with
400° molten solder. Again, do the right thing.
of the most important steps in any project is to organize
all the tools and materials you will need, and make sure you
have everything. Getting halfway through a project and realizing
you are missing a tool, or something like the last battery
bar, can be rather annoying. Preparation is the key to success,
in all aspects of life.
Hair Dryer or Heat Gun
Iron 40w-60w with a 1/4" chisel tip
1: Getting Started
lay out your cells and put the single cell shrink-wrap on
them. The extra shrink wrap will help protect the cell, and
allow the Shoe-Goo to be removed in the future without destroying
the matcher label.
2: Applying the shrink wrap
might be wondering what you'll need gloves for when assembling
battery packs. Well, I use them to hold the cell while I heat
the shrink-wrap. That hair dryer gets pretty hot when holding
it 1-2" away from the cells, and the gloves keep that
heat off your hands. Here, I'm wearing Craftsman mechanic's
gloves, which are perfect for this application.
are before and after shots of the individual cell shrink-wrap
3: Scuffing the cells
you need to scuff the ends of the cell so the solder can get
a firm grip.
you see before and after shots of the cell that I scuffed
up with the X-Acto knife. Scratch it up really well good,
as this is critical to a good solder joint.
A popular hobby blade is the #11 from X-Acto. I find the #11
to be too thin to do a good job here. A #2 is much more effective
and durable for this job.
4: Laying out the pack
you need to decide the orientation of your cells. I recently
purchased a Novak Smart Tray, and I found most of my packs
were assembled in the exact WRONG orientation. I had the wires
attached in such a way that it made inserting the pack into
the tray very difficult. So stop for a second, plan this out,
and get it right the first time.
5: Preparing to solder
you need to apply a small amount of flux to the end of each
cell. Use as little as possible, as this stuff goes a long
way and is quite messy. A Q-Tip is a great way to control
it. Toothpicks work too..
6: Applying the solder
it's time to apply a 1/8" sized drop of solder to each
cell, which will promote good adhesion. Some people don't
do this, but I find it to be the easiest way to build a strong
pack. You can either apply it as a little ball, or spread
it around thinly. Either way works the same in the end. If
you manage to make too big a solder blob, then you can easily
remove it with the desoldering braid (Item #16). It's a good
idea to clean the tip of your iron everytime you make a new
joint by rubbing it on a damp sponge. This helps eliminate
pollutants and gives you a cleaner joint.
7: Attaching the bars
place one of the bars across 2 cells and apply the bar holder
to it. Try to center the holes of the bar on the solder you
apply heat for more than 5 seconds, as that will damage the
cell. If you must redo the solder joint, move on
to the next bar and then come back to it after the cell has
cooled completely. Touch the tip of your iron to the + or
- on the bar for 2 seconds to heat it up, then, while still
holding the iron on the bar, apply just a bit of additional
solder to get the joint to flow smoothly. Remove it as soon
as the pressure from the bar holder is able to press the bar
fully onto the cell. This will occur when the solder you applied
to the cell earlier melts.
Pressing on the bar holder with your finger will help ensure
a strong mechanical connection between the bar and the cell.
8: Checking the joints
with all the bars attached on this side, I take the X-Acto
knife and give a fairly forceful tug. If I can break it loose,
so can the guys I'm racing in the A-main. Get it right the
first time. Be careful here, as the bar can sometimes fly
off the cells! Eye protection folks, use it...
9: The flip!
it's time to flip the jig over and work on the other side.
Be very careful to start soldering on the correct cells. After
the flip, tilt the jig up and visually trace the circuit you
need to complete.
Notice I actually do wear the vinyl gloves I mentioned in
the safety note earlier? Working with hazardous materials,
such as solder and flux, should not be taken lightly.
10: Attaching the pigtail
that your pack is complete, it's time to attach the pigtail
if you choose to go with plugs instead of hard-wiring. Deans
are the plugs I choose, however this works for whatever brand
of plugs you prefer.
the leads is critical to a strong solder joint.
the heat is too much for you to handle, use a heatsink clip
to hold the wire. I don't use them, as I find my own ability
to handle the pain is about the same as what I'd want to inflict
upon a valuable cell. Sometimes this is a difficult joint
to complete and it takes a few tries. If I find it's getting
too hot for me, then I stop so the cell can cool and try again
in a few minutes.
now apply a bead of Shoe-Goo between each pair of cells. I
probably use too much, but I like a nice, strong joint. Your
milleage may vary..
There you have it, my simple steps to assembling a race pack.
Others may have different techniques, and their work might
look cleaner than mine, but this works for me. I hope someone
learns something from this.
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