Let me get this off my chest right up front. I’m not a fan of the Dean’s Ultra connector. Yes, they’re the hobby standard, they’re inexpensive, and they work well, but they’re hard to get apart and they are a pain to solder correctly.

Thus, I have changed all of my LiPo connectors over to the EC3 connector. Sold by E-Flite and Align, among others, the EC3 is rated at 60 amps, connects and pulls apart with ease, and is a snap (literally) to solder on. The best thing is, they pose less of a risk of shorting during the soldering operation than a Deans.

I say they’re easy to solder on now, but I ruined many an EC3 learning how do do it correctly. To that end, I thought I would share my method with our readers who may be interested in making the switch and perhaps spare them some aggravation.

The Tools

You can’t do a good job without the correct tools, right? Here’s what you’ll need to get the job done:

Soldering iron – I use an adjustable 40watt Weller (turned down to around 30W) with a #3 chisel tip.

Solder – I use fine rosin core solder form Radio Shack for almost everything.

Wire Stripper – Used for trimming the insulation from battery or component leads.

Helping Hands – If you don’t have a set of these, go to the store right now and buy some. I’ll wait…

Small Regular-bladed  precision type Screwdriver – You’ll see why in a bit. I use a jeweler’s screwdriver.

Choosing the correct connector

Like most electrical connectors of this type, there are two different types of EC3. The “male” connector is soldered to the leads coming from components such as chargers and ESCs. The “female” connector is the one that’s attached to batteries. See the picture to tell the difference. Notice that the EC3 shells are indexed, having one square and one round half, so as to prevent reversing polarity. Note that the red (positive) wire goes in the square half and the black (negative) goes to the round. If you forget, the connector shells are marked to indicate their polarity.

The contact portion of the connector are gold-plated bullet connectors of very high quality and low resistance. For this article, I’ll be showing how to solder a female  EC3 to a battery. The process for the male connector is the same.

First, turn on your soldering iron and let it start warming up. Next, grab a bullet connector and clip it into the helping hands as shown. (some guys use a 2×4 and drill small holes in them to hold these for soldering) Be mindful of the end you’ll be soldering. Each connector has one deep and one shallow end. The shallow end has radial rings on the outside of the bullet. We will be pre-filling this end with solder.

One of the reasons I prefer a chisel tip on my soldering iron for soldering connectors is because it has a flat surface that conducts heat well. Good soldering is all about heat transfer and a tinned flat surface transfers heat faster and better than a sharp pointy one. Take the flat edge of your soldering iron and put it to the rim of the connector as shown in the picture. After a few seconds, the connector will be hot enough to melt the solder. Place the solder end down into the cup and it should start to melt rapidly. You will be filling the end about halfway. We’ll be putting a thick wire in here later and if we have too much solder in the cup, it will be forced out and flow down the outside of the connector. You must be careful not to get any solder on the outside of the bullet or it will not lock into the shell properly.

New battery packs generally come with shrink tubing on the ends of their unterminated wires to prevent shorting. If yours is like this, take the shrink tubing off of ONE of the leads only. Usually, about 3 – 4 mm of the wire will be stripped and tinned, but check to make sure that the tinned wire will fit into the end of the bullet. Trim it carefully if it will not.

Next take the soldering iron and reheat the bullet just as you did when filling it with solder, while keeping the wire ready to put in. Once the solder in the bullet re-melts, pull the iron out of the way and quickly but carefully insert the tinned wire end and hold it still for a few seconds to let the solder cool and the joint solidify. You’ll know you got a good joint when the wire in your fingers gets warm. Once you think it’s suitably cool, give a firm tug on the bullet to make sure it’s secure. Again, be very careful not to get any solder on the outside of the bullet connector.

Once the bullet connector has cooled, we will be inserting it into the shell. We don’t want any loose battery ends that could possibly short on anything. By putting it in the shell before soldering on the other bullet, we’ll be assuring that shorting won’t happen.

Being careful to match the wire you’ve soldered to the correct connector shell side, insert the bullet into the back side of the shell. Holding the shell open-end down on a hard surface, take your screwdriver and insert it in between the wire and the shell body, so that the tip of the screwdriver contacts the back edge of the bullet connector. Now, push down with the screwdriver until you feel the bullet snap into place. You should also hear an audible *snap*. Note that you will need to push fairly hard, so don’t be afraid. To verify that the bullet is properly locked into place, hold the wire and give the shell a twist. You should be able to freely spin the wire inside the connector (or more precisely, the shell should spin freely on the end of the wire). Additionally, your bullet connector should appear inside the shell as shown if the picture.

Simply repeat the this procedure for the remaining wire, and you’re done! Behold the finished product!

Hopefully this has helped take some of the difficulty out of soldering these connectors on. They’re a bit more expensive than Deans connectors, so ruining them while learning how to correctly install them can be aggravating. Follow these steps and you’ll be a master EC3 installer in no time!

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