ABCs of connectors
ASSEMBLE YOUR CONNECTORS WELL WITH GOOD SOLDERING FOR LOW RESISTANCE
Modern connectors come in two basic types: those with flat blade-style contacts and those with round pin-and-socket contacts, known as bullet connectors. Both styles have advantages and disadvantages, and making a choice can be difficult.
BULLET CONNECTORS
There are quite a few types of bullet connectors available today. In their simplest form, they’re used plain and almost bare, with the pin, or male, part of the housing completely uncovered so that it can plug into the socket, or female part. The socket and the base of the pin should be covered by heat-shrink tubing so that the connected pair is fully insulated. With care they can be used safely, but there is no standard orientation for them, and that can lead to problems. I have shorted plain bullet connectors before and seen others do it, and it’s no fun.
A solution for some of the shortcomings of the plain bullet connector is to develop a housing that protects the connectors from coming into unwanted contact, insulates them both in use and storage, polarizes them so that it’s not possible to plug them together in the wrong orientation, and helps the user grip them for connecting and disconnecting. Not surprisingly, there have been several different designs brought to market, so the electric-power flier has a wide range of choices.
EC CONNECTORS
Horizon Hobby uses blue EC3 and EC5 connectors, which are bullet connectors snapped into a polarized housing. The EC3 uses a 3.5mm connector and is rated at 60 amps. The EC5 has 5mm bullet connectors and is rated at 120A. Both connectors share the same basic shape and are assembled similarly. The wires and connectors are soldered
together and then the connectors snap securely into the housings. They’re impossible to connect incorrectly, are easy to grip and use, and provide good protection from electrical shorts.
XT CONNECTORS
XT connectors are bullet connectors that are molded into a uniquely shaped yellow nylon housing. XT60s have 3.5mm bullet connectors with a rating of 60A, while XT90s have a 5mm bullet and 90A rating. Since the connectors are molded into the housing when manufactured, wire is soldered to them in place and covered with heat-shrink tubing to insulate the bases of the connectors. Some XT connectors have a molded cover that snaps to the base of the plug and provides insulation for the wires. They’re easy to assemble, are well polarized to prevent connection mistakes, and have good gripping surfaces.
POLARIZED CASTLE CONNECTORS
Castle Creations has a green plastic connector housing offered in a couple of sizes. The smaller one uses 4mm bullet connectors and is rated at 75A. The large size carries 6.5mm bullets and has a 200A rating. Both sizes are polarized, are easy to grip, offer great protection, and use Castle’s solid pin contact design instead of a spring design. To assemble them, the wires are passed through the housing and soldered into the cups on the base of the connectors. Then the connectors snap securely into the housings. Castle also sells bare bullet connectors in 4mm, 5.5mm, 6.5mm, and 8mm sizes, which are well suited for connections between the speed control and motor.
FLAT BLADE CONNECTORS
A second type of contact utilizes flat connectors. Electrical connection is made by two blades of conductive metal sliding together that are held in tight contact by a spring in the housing. Like bullet connectors, these connectors have good connection properties when properly assembled.
T-PLUG CONNECTORS
These connectors get their name because the orientation of the blades in the molded body resembles the letter “T.” The Deans Ultra plug was the first of this style and has been in wide use in electric-power equipment since the late 1990s. The company doesn’t publish a current rating, but many people who use them consider 50 or 60 amps to be a good limit. To assemble a T-plug, the wires are laid on the flat blade and soldered to it, then covered with heat-shrink tubing for insulation. Some people who use them have trouble disconnecting them, and they can be fiddly to solder properly. They are polarized, so plugging them together incorrectly is very hard to do.
Hobbico’s Star Plug is an improved variant of the T-plug, with a nicely shaped housing that has grips molded in. There’s a rear cap with a center isolator that snaps securely onto the housing to separate and insulate the wires, and it provides additional gripping area for easier disconnection.
ANDERSON POWERPOLES
Anderson Powerpole connectors are flatbladed pin connectors that have cups formed into the rear for wire insertion. They can be soldered or crimped, and the pin snaps into a plastic housing that can key into other housings to make polarized plugs in several variations. Powerpoles come in 15-, 30-, and 45-amp pins that all fit into the same housing. Used singly they’re not polarized at all, and are easy to connect improperly, causing dangerous shorts. I know; I’ve done it myself several times.
That said, I’ve used Powerpoles for going on 30 years. I bought a crimper from West Mountain Radio that makes them fast and easy to assemble, with a better connection than soldering. Since I’ve started always keying the individual housings together to make polarized plugs, they’re perfectly safe, even for me. I’ve found them to be conservatively rated by Anderson, and I use the 45-amp connector regularly in power systems that exceed 75 amps with no heat buildup or other problems.
ADAPTERS
“Hey, I left my charger at home. Can I use yours?” “Do you have a 3-cell battery I can use for a flight?” I can’t tell you how many times I’ve been asked these questions, and with all the different types of plugs used by different vendors, it’s often hard to say “yes” because my connectors aren’t compatible with theirs. Adapters are the solution.
Adapters are simply one type of connector (the one that you use the most) connected to another type. They can be at either end of lengths of wire, or soldered directly together if possible. After a while, a modeler can end up with quite the collection of adapters.
BOTTOM LINE
One of the nice things about being an electricpower flier today is the wide variety of choices we have in connectors as well as in other gear. That wasn’t the case when I was starting out.
I’ve standardized on Anderson Powerpoles for battery and charger connections, and plain bullets for speed-control-to-motor connections since they don’t get disconnected often. If I were just getting into electric power today, I’d use one of the bullet connector housings as they’re all good choices. All the types discussed here have good contact resistance for reasonably low losses if used within their ratings. Regardless of which connector you choose, it’s important to learn how to assemble them well, with good soldering for low-resistance connections.