DEANS ULTRA VS. POWERPOLE
While both of these are excellent connectors, some people shy away from the Deans simply because of the perceived difficulty in soldering. They can be tricky for the novice and you can easily destroy the connector if you are not careful. I prefer them due to the size, a bit more compact than the POWERPOLE. Here is the soldering technique I use.

First you need the proper tools. A 40W soldering iron with a ¼” chisel tip, iron holder, wet sponge to clean iron, helping hands, and of course some rosin core solder and solder paste. Do not use acid core solder or paste!

Fig 1. Soldering tools

Prep the Deans by tinning the positive and negative terminals on the side you will be soldering to.

(step 1) Strip the positive wire 1/8” from the end, and then twist with a rolling motion of your thumb and forefinger, the exposed copper strands so that there are no strays. Next (step 2) Tin the wire with a good soldering iron, I recommend a 40 Watt iron with a ¼” chisel tip for good heat transfer. You should also have a wet kitchen sponge and a wad of steel wool in a small can to frequently clean the tip. Lay the wire on the side of the iron tip and just touch where the wire touches the iron with rosin core solder. A word of caution here. If soldering to battery leads do ONE AT A TIME to avoid shorting the leads. Starting with the positive wire (red) take the tinned lead and compress it in a small bench vice (step 3) or with a pair of vice grips so that it forms a flat surface (step 4). This flat surface then is positioned (step 5) with some “alligator hands” on the inside surface of the previously tinned surface of the positive terminal of the Deans (the one that is crossways, usually marked “+” except on some poor quality imported copies). Oops, don’t forget to put a ½ inch piece of 3/16 dia. heat shrink on the wire before you put it in place. Now apply the freshly tinned tip of the iron to the junction of the wire (step 6) and the terminal for just a second or so until the solder flows and makes the bond (step 7) .
Figure 3. Deans soldering sequence 7-9

Once soldered, slip the heat shrink over the joint (step 8) and shrink with your heat gun. Now you are ready to do the negative connection in the same manner. Tin the terminal. Note that the negative connector (the one running up and down) is slightly offset. Position the tinned and flattened wire against the terminal where there is the most
space and solder as before. When cool slide the heat shrink over the joint and shrink it in place. There you have it (step 9) a finished battery pack. Oh, that little hole in the connector is to allow you to use snap ring pliers to separate the connectors. A little Vaseline wiped on the pins helps here also.