Ohm’s Law states that the voltage and current flowing through a wire are related to the resistance offered to the current. As resistance increases either the voltage or the current must change. The connections between wires are often the source of unwanted resistance that reduces the available voltage, and this is a particular problem when the voltage is already low. Consequently, poor connections should be avoided. The best connection between two, three or more low-voltage cables is produced by a perfectly soldered joint, something anyone can achieve with a little practice. Connect three cables in the same way as you would two low-voltage cables.
Switch on a soldering iron or gun, and allow it to reach its operating temperature. Touch the end of a solder rod to the tip of the iron and allow a small ball of molten solder to form on the tip of the iron. Rub the tip of the iron on a damp sponge to smear the molten solder all over the tip of the iron and to remove any debris, oxidized metal and dirt from the iron. This is called tinning, and the result should be an even coating of shiny solder all over the tip of the soldering iron.
Wrap the entire joint in electrical insulating tape once it is cool, to protect it from corrosion and damp.