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-   -   Barrel connectors- What's the current rating? (https://www.rcuniverse.com/forum/questions-answers-154/5322897-barrel-connectors-whats-current-rating.html)

74Rallye 01-25-2007 07:00 PM

Barrel connectors- What's the current rating?
What are the current ratings for barrel connectors used for the ESC to motor connection? I have 3.5mm connectors on everything I've got. I'm putting a 350 Watt setup in a new plane and I would like to keep everything interchangeable. What size should I use? Thanks.

N1EDM 01-26-2007 01:52 AM

RE: Barrel connectors- What's the current rating?
I thought there was a magazine article from MAN on this a few years back. I just searched their website but could not find it.

A more important question to ask is how much current the contacts can carry, not how many watts. Higher voltage will use less current for the same wattage (P = E x I). Current produces heat when the contacts can't carry enough electrons through them.

On a hunch, I'd say that the 3.5mm contacts should be OK for a 350W setup, but in real life, more info is needed. What's the size of your pack?

Does anyone else know where we can find that article that I was referring to (above)?


74Rallye 01-26-2007 05:40 PM

RE: Barrel connectors- What's the current rating?
I use 3S 20C in 3200mAh and 2100mAh sizes. I've heated up the 2100mAh pack and warmed the 3200mAh. I know I should solder the wires, but plugs are nice.

N1EDM 01-27-2007 02:46 PM

RE: Barrel connectors- What's the current rating?
If the connectors are properly installed, my opinion is that heating up of the pack indicates that you're drawing a lot of current, perhaps more than it's capacity. Some heating is normal as long as it's not beyond the manufacturer's recommendation.

The "contacts" article I was looking for in Post #2 was actually on FlyRC, March 2004, page 46. They talk about Gold Bullet" connectors on Page 48 being rated at 70A. I assume those are the 4.0mm contacts (though they don't mention by name). I am interpolating their article to read that a 3.5mm contact is good for about 40A. But, that's just my own interpolation.

I should also mention this. I've been in the connector industry for many, many years. It doesn't matter whether you solder or crimp (flamers, hold off and read on before you push those buttons). A properly crimped contact is just as good as a properly soldered contact. Notice that I used the word "properly" twice. The problem is, when making up crimped connectors, many fliers mash the crimp barrels with pliers or something that is 'sorta close'. That just ain't gonna work. You have to use the crimp tool specifically made for that contact or you can just forget about it. Properly designed crimp tools are very expensive.

The same can be said for an improperly soldered connector. Trying to glob solder onto dirty wires or wire barrels results in cold solder joints that also work poorly, and then the flier blames the batteries, motor, esc. Again, refer to the "F" word in the paragraph above.

Anything less than a properly crimped or soldered connector is just wishful thinking. Wishful thinking doesn't let enough electrons pass through.

In short, one should use a proper crimp tool or the proper heat (i.e., not too high, not too low) when soldering. Overheating a contact can cause the contact leafs to lose their 'springiness' and not make sufficient contact. Overheating of the connector is a result.

I don't think that a poor connector joint will overheat a battery. The contacts should get no warmer than the surrounding wiring going in and out of them.

There you go, you asked me the time and I told you how to build a watch. I'm not saying that you fall into this category, it was just my way of mentioning some things...


oceansfiftyseven 01-28-2007 06:31 AM

RE: Barrel connectors- What's the current rating?
I have used the 2.5's up to 400 watts on 4s lipos without any issues. Your 3.5's should be fine. The wires coming out of the motor are often coated with resin. I sand off the resin and wipe with alcohol before soldering.

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