Hint: 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.

A 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.

Organize your workspace

One 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.

1. Hair Dryer or Heat Gun
2. Deans Battery Jig
3. Soldering Iron – 40w-60w with a 1/4" chisel tip
4. Cells
5. Wire Strippers
6. X-Acto knife
7. Solder
8. Individual cell shrink-wrap
9. Battery Bars
10. Pigtail
11. Rosin flux
12. Q-Tips
13. Heatsink Clips
14. Shoe-Goo
15. Gloves
16. Desoldering Braid

Step 1: Getting Started

First, 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.

You 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.

Below are before and after shots of the individual cell shrink-wrap being applied.

Step 3: Scuffing the cells

Next, you need to scuff the ends of the cell so the solder can get a firm grip.

Here 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.

Hint: 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.

Step 4: Laying out the pack

Now 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.

Next 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..

Now 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.

Now, 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 just applied.

Never 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.

Hint: Pressing on the bar holder with your finger will help ensure a strong mechanical connection between the bar and the cell.

Now, 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...

Step 9: The flip!

Now 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.

Hint: 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.

Step 10: Attaching the pigtail

Now 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.

Pre-tinning the leads is critical to a strong solder joint.

If 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.

I 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..

Final thoughts:
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.

Good luck folks!