RRCi Focuses On Connectors.

Why is it that every electric RTR kit these days comes with the Tamiya style connector fitted, because they have been in the game since the beginning and it is become the industry standard, but is it any good?

In light of the recent developments since the BRCA AGM where a special committee decision was made to outlaw direct soldering of power sources to vehicles on safety grounds. All the top pro drivers directly solder batteries to speed controllers for minimal losses, in spite of the fiddly, time consuming and downright inconvenience of it, the maximum current flow pays dividends in acceleration and top speed, which are worth every second spent on the pit table.

Us mere mortals are quite happy to just plug and play, but should we be content with what we are handed? Can it be that much different from connector to connector?

A typical 1/10th electric vehicle will use most of a 3300 mAh pack in a five minute race and battery pack capacity is expanding ever upwards so the motors are decreasing in winds to make use of this extra capacity, putting more and more load on the connections in between.

To find out which connectors did the best job and what benefits they might have to offer we devised two tests using the CBA II from Aurorra Ltd, my faithful 'battery dyno', which I take everywhere with me. Our test equipment was a fully charged 5000 mAh Venom LiPo as the power source, loaded by the CBA II battery dyno set to a 10 amp drain your average RTR drain, running a 2000 mAh pack fl at in ten minutes.

To monitor the connectors under load we used an HPI Infrared temperature gauge set to monitor the maximum temperature in degrees Centigrade and hold it for easy reading. All this is stuff anyone can get their hands on if they want to try this test for themselves! In a race situation a typical 4000 mAh discharge takes place over the course of a 5 minute race, that's an average of 50 amps, and with a data logger attached to a 1/10th touring car we saw spikes of over 200 amps, so you see whatever a 10 amp drain test reveals will be multiplied many times under racing conditions.

UNDER LOAD

We took several well known connectors to compare to the industry standard Tamiya plug, including the old style 'Power Poles', the more recently popular 'Deans' style, the racers favourite Corally style gold tubes and the new Traxxas High Current fl at blade.

First, the wiggle test, whereby the wires are jiggled lightly like they would be when the R/C vehicle is in motion, over obstacles, rough ground, cornering hard, accelerating, braking or colliding. Any movement in the discharge curve indicates an insecure connection which might manifest itself in a number of ways including stuttering, limited power, apparent 'interference', power surges or even a complete loss of power altogether.

Secondly, any temperature rise in the connector is a sure sign of resistance, the higher the temperature rise at a constant current the higher the resistance in the connection and the lower the voltage will drop as a consequence, limiting speed, acceleration and endurance as a direct result. Displayed on our readout as a drop in voltage hold up under load.

Most power connectors are designed to be user friendly and idiot proof, because not many electrical systems will put up with being plugged in backwards, so the first job of any RTR connector is to protect the equipment from first time users and their predictable misadventures. The Tamiya connector does this, as does the Deans and Traxxas plugs, the Corally tube connector can be installed in a number of ways, but most sensibly with a male and female on the battery and a male/ female on all the speedo/charger/discharger equipment you intend to use, to prevent you plugging in backwards as you might if two tubes are used for negative and positive on the battery, ask me how I know!

It should be noted that the wires themselves reached 28C under 10 A loads, so any connector that matched that should be considered as good as it gets!

TAMIYA PLUG

Temperature rose quickly to over 40C before test was aborted. Voltage dropped below 7 V under load showing a high resistance, and it failed the wiggle test badly, as the voltage graph leapt about wildly with a simple tap on the connectors.

Easy to plug in and latch together, simple to disconnect, completely idiot proof and impossible to connect backwards once soldered in place properly. The connector is big enough to grab hold of when disconnecting without stressing the wires.

Tricky to fit, as the wires need crimping into the pins and then soldering for security, before pushing into their housings, pretty tricky to assemble and disassemble, twin barbs hold each pin in their housing. In use I've had many Tamiya connections push out of their housing, when the barbs dig through the material as it softens with the temperature rise and even melts causing a short circuit as the pins wander within.

POWER POLES

Temperature steady at 28C and passed wiggle test! Easy to grab hold of when disconnecting without stressing the wires so it disconnects easily and is reverse connection proof when assembled correctly. Easy to assemble to connectors, soldering onto wires was a breeze, and slid neatly into housing with a pleasing and confident click. Easy to disassemble with just the tip of a sharp blade to lift the connection over its latching plate, and slide out the back. I have yet to have a power pole fail on me whether in operation or through overheating, though I have had a couple of housings crack apart with age and the occasional dousing in motor cleaner which appears to attack the plastic.

DEANS STYLE

Settled at just 31.3C and passed the wiggle test. The Deans style plugs are quite small and you usually end up tugging the wires to get them apart which is far from ideal. If your pins are tough to get together and even harder to pull apart your pins have most probably wandered in their housing, either whilst under load but more probably during assembly. Use a high wattage soldering iron and keep it to just a short duration on each pin, enough to get the solder to flow but short enough to keep the pin from melting the surrounding plastic, I even go so far as to attach a pair of mole grips to the pin as a heat sink! Simple to assemble, just solder on and heat shrink over the connections, though soldering the wires in place can be tricky and prolonged heat applications can melt the housing and allow the pins to wander, ruining the location and therefore the connection.

TRAXXAS HIGH CURRENT FLAT BLADE

Crept up to a steady 28C and passed wiggle test. Traxxas flat blade connectors slide apart real easily, and are large enough to grab a hold so you don't have to pull on the wires.

Assembling the connectors can be fiddly, getting the right pins in the right housings, and the right way up, though it is written on each pin, 'A' for the male, 'B' for the female, and 'WIRE SIDE' stamped clearly on each pin, but all this is covered up once you tin the connection with solder so you need to be sure of your layout so you can keep track of which pin goes where. Also crossing the marked 'Solder Line' with either solder or wires results in the pins not completely seated in the housing and failing to latch home, so you need to simply fl at it back to the line with a Dremel. Disassembly is easy, just like the Power Poles, requiring just a point of a blade to lift the blades over their latches.

MICRO CONNECTORS

It's not just the big cars that draw high loads through tiny connectors; the problem is often compounded on smaller scale cars, as there isn't room for a big power connector.

Take your typical 7.2 V 1300 mAh micro battery, in just 5 minutes it is usually close to dumping, working out to an average current draw of 15 A, and with a data logger connected we saw spikes in excess of 25 A, so a mere 10 A draw is reasonably kind and totally possible during race conditions. The problem is twofold as these square connectors are also used for connecting to the motor itself, which can usually be simply cut off and soldered, direct from ESC to motor terminals.

TYPICAL SQUARE RTR SPEC MICRO CONNECTOR

Temperature rose to 69C before test could be aborted, and it failed the wiggle test; a sure sign of a poor connection. The miniscule connector pins offer a tiny surface area with high resistance that limits current flow and hence drops the voltage across the connector. Therefore it gets increasingly hot as the current continues to struggle across the gap.

MICRO CORALLY STYLE TUBES 3.5 MM

Recorded a constant 32C and passed wiggle test.

As simple to use and install as its larger 4 mm brothers.

As a consequence all my micro power packs, and for that matter all my receiver power packs for nitro models have been converted to mini Corally style 3.5 mm tubes for this very reason, even replacing the usual radio switch, just leaving either the positive or negative outside the radio box for easy connection and disconnection between races. I even use them to connect micro brushless motors to their speed controllers for easy maintenance and removal, motor swaps etc. Highly recommended. I even install them on receiver LiPo packs and their regulators, as some high torque servos are pulling some serious current in 1/8th off road buggies and truggies these days and require a regulator capable of delivering 3 A or more so I wouldn't want to trust the connection to anything less than a totally dependable unit. Would you?

CORALLY STYLE 4 MM GOLD TUBES

Creeping up to 28C by the end of the test, showing total efficiency with minimum losses and sure enough it passed the wiggle test.

Pulling the connection apart is easy, one at a time, and there is plenty of plug body to grab hold of without stressing the wires themselves. Assembly is a breeze, with the wire simply soldered into the back of the tube and then heat shrink covered to prevent any short circuits, covering the whole tube of the female connectors and just the shoulder of the male pins. Disassembly is a breeze, simply cut away the heat shrink and de-solder the wires. Venom, have recently come up with a clever variation on the Corally tube theme, with twin connectors, clipped into moulded pairs for an idiot proof and simple connection. They could be onto a winner there!

LET IT REV!

As a final test, we took the best and the worst and re created racing conditions using a Robitronic Motor Dyno powered by a 12 V lead acid battery so it had all the amps on tap that it could possibly draw, and a 10x3 motor to really ramp up the load. We wired the power from control box to motor via a Tamiya plug and then via Corally style 4 mm Gold tubes to see what real time effects the resistance of the connector had on torque, acceleration, power and revs. The results speak for themselves, look at the Tamiya plugs loss of torque, almost 20 Nmm down, and you'll also see that 30 W of power and almost 1000 rpm went missing! The max current draw tells the main story, with the Corally style tubes able to pull 132 A compared to the Tamiya 100 A, and right below that display you can make out the resistance the system recorded, whereby the Tamiya at 30 mOhms was double the Corally tubes 15 mOhms.

So regardless of what scale you race with, whether on road or off road, next time you are looking for a little more whoosh, take a good look at your power connectors! Fit a high current capable power plug to your batteries and ESC, and direct solder the ESC to your motor, losing any plugs or bullet connectors in between. It could be the difference between winning and losing!