steps to a straight, tight pack
you're buying expensive matched cells for your race machine,
you probably don't want to goof them up (or worse, reduce
their performance) by doing a hack soldering job. Here's how
to build a tight, straight, clean pack that will fit in your
car properly and deliver maximum performance.
By Greg Vogel
It's a snap to
build your own packs. To make this job easy, I suggest using
equipment of the same quality as shown here. A wood-burning
iron from a hobby store may be able to melt solder, but it
won't work well enough to heat all the components at once,
which is what you'll need to do a good job. And building a
pack without a jig may result in misaligned cells that won't
fit in the chassis. You only want to do this once, so do it
right. Take your time, and use the right tools.
Gather all the equipment you'll need: heat-shrink wrap,
heat gun, X-Acto knife, solder, soldering iron, battery jig,
battery bars, wire and connectors (if applicable).
To keep the cells' labels clean on a Trinity* matched
pack and help prevent the chassis from marring the original
covering or causing shorts, simply slide a piece of wrap over
the cells and blast it with a heat gun or a hair dryer to
Scuff the ends of the cells with a Scotch-Brite pad,
fine sandpaper, or—in a pinch—use your X-Acto knife to
scratch their ends; this will give the solder something to
Tin both ends of each cell with good-quality solder such
as Acer Racing's* silver solder (shown here). I'm using an
Ungar* Race Station for the soldering duties. This iron has a
knob to adjust temperature, and at its hottest setting, it can
quickly melt solder onto the cells. Don't hold the iron on the
cells for long because excessive heating can damage them.
The easiest way to assemble a pack is in a jig—here, a
Deans* jig. Now is the time to determine how the pack will sit
in your car. Normally, the positive lead is in the back of an
off-road car; use the cell layout patterns as a guide; a
saddle pack's positive lead will be closest to the ESC.
Remember: keep the labels facing up; it's just the cool thing
to do. Place the cells in the jig so the positives will be
soldered to the negatives.
Place a battery bar across the cells, as shown here, and
place the spring clip over the bar to anchor it. Hold the iron
on one side of the bar and feed a little solder onto the top
of it. If you don't use a Deans jig, quickly put down the
solder after you've applied it to the cell, and use the X-Acto
knife to hold the bar while you remove the iron from it. When
you've completed one side of the bar, follow the same
procedure for the other side and for the rest of the pack.
When you flip the pack over, be careful not to place a bar
across two cells that have already been soldered together.
Remember, you're completing a "loop" between the
You've pretty much finished. If you're hard-wiring the
pack into your car, take a battery bar and bend its top
quarter over at a 90-degree angle. Solder the long end to the
battery pack; solder the wire from your ESC to the bent
portion. Connectors are easy to install, too; simply solder
the positive side of the plug to the positive side of the
battery, then repeat the procedure for the negative.