Electric Power questions: Soldering secrets

May 10, 2011 5 Comments by
I was told that soldering a plug onto a LiPo battery could result in puffing the pack or even a fire. Is this true?
Brent Paul [email]

You can puff the battery by getting the wire too hot from soldering, but if you set it on fire, you might be better off never touching a soldering iron again. Consider buying packs with the plug you need already installed; however, most modelers are very adept at building skills and should have no trouble learning the proper soldering technique for battery packs. The first thing you have to be aware of is that heat is the enemy of your battery, so don’t let it get hot.

To prevent heat buildup, you must develop good soldering skills. I stick to a regimented soldering technique when installing plugs at the end of the wire leads from a pack. I prefer to use the same plug for all of my electrical connections just to make life easier. On smaller backyard flyers with packs 1500mAh or smaller, I use Deans Micro Plugs. On larger planes, I use Deans Ultra Plugs. Because they have a very small space between the soldering tabs, I install only one wire at a time to prevent the pack from shorting. I always begin by securing the plug in a third-hand-type of device so that it doesn’t move. Before I strip off a little wire covering from the ends of the leads, I slide shrink tubing over both lead wires all the way down to the pack. Starting with the red wire, I strip off about 1/4 inch of covering. Then I secure that in the other alligator clip on my third-hand device.

The Deans micro plugs are indentical for the battery and ESC; using a different color shrink tubing helps to keep the polarity correct.

To start the soldering process, first apply a little solder to the tip of the soldering iron and then place the tip at the end of the wire lead. Working quickly, apply the solder from the tip onto the end of the lead and then back over the bare wire. By starting with the melted solder on the tip, you can cover the entire area of bare wire with solder within a matter of seconds. This keeps the temperature from traveling down the wire leads to the battery pack. Next, move the iron tip to the plug lead and add enough solder to form a small bead of solder on the plug’s metal tab. Using a pair of needle-nose pliers, grab the wire-lead covering near the bare wire and push the lead onto the plug tap with the bead of solder on it. Press the tip of the soldering iron onto the wire lead, and keep it there just long enough for the solder to melt on the wire lead and the plug’s metal tab so that a good solder joint forms. This should take only 1 to 2 seconds. Hold the wire lead in place with the needle-nose pliers until the solder solidifies. Give it a slight tug just to make sure that you have a good solid joint.

Before I started the second wire, the first wire is already done and wrapped with shrink tubing to prevent any shorting out. Don't forget to have the shrink tubing on the wire before you solder.

After it cools for a bit, slide shrink tubing over the bare wire and plug tab, and heat it with a heat gun so that you have a finished, covered solder joint. Now you can strip the black lead and perform the same procedure to make a nice solid solder joint on both tabs of the plug. By soldering and covering one tab at a time, you avoid any accidental arcing caused by the soldering iron or melted solder. I’ve soldered more than 100 plugs on battery leads, and I’ve never had trouble using this technique

With a bead of solder on the lead wire and plug tab, gently push down on both with the soldering iron until they melt together.

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About the author

West Coast senior editor About me: I’ve been involved with RC aircraft since high school and have flown just about everything. I started my RC career with scratch-building, but now like many pilots I rely on ARFs to get me in the air. My main focus is on pylon racing, aerobats, combat and scale warbirds.

5 Responses to “Electric Power questions: Soldering secrets”

  1. Anonymous says:

    Excellent article. Keep these coming.


  2. eff says:

    would it be possible to have the tip in video, thanks in advance

  3. John Reid says:

    that would be a good one to do

  4. Allen B says:

    One thing I don’t see in these “How to’s” is that you should ALWAYS use a heat shunt on the battery side wire when you solder. You can purchase one at a Radio Shack or similar electronics store. It won’t keep all of the heat from traveling up the wire, but it will help. Alligator clips will work, also, but don’t have the broad blades to help dissipate heat.

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