Large spark from XT90 connectors

Quinton

Active Member
Easy to solder four wires to each of the battery pads on the Droidworx PDB so you can run four packs.

Also of interest - look at the pic on page 8 of that manual - the right hand ESC of the three facing you - the red wire is certainly exceeding the minimum bend radius for the wire and will be vulnerable to breaking strands internally. On the left, underneath the ESC, they've got a wire passing down through a hole in the carbon fibre plate - that should be protected with a grommet or sleeve so the insulation can't chafe against the sharp edge. And the left-most capacitor - the top looks like it's already swelling - it should be replaced! Anal little details like these keep you in the air :)

Have you seen the DRW PDB there is not much room in there for the 2 wires, never mind 4?
You also have to leave enough room, so you can screw the 8 holes at the outer diameter to the stand offs, which you need to be careful with even with 2x 10AWG wires.
Also you don't really have much of a choice but to bend the wires under. (Have no idea why their wires are going down through that hole, as the solderpoints are underneath the board that the ESCs are sitting on.
How else could you do it, without having the wires bent from top to underneath it?
 

jes1111

Active Member
The issue is the length of wire you leave between the ESC and the solder pad - just leave a bit more so the cable can "loop" gently rather than need to be folded over hard like the one(s) in that picture.

If you have the board in front of you, can you measure the +/- pads? 10AWG multistrand wire is about 5mm diameter, so if the pads are 20mm wide there's no problem. If they are narrower than 20mm then you can flatten the stripped ends and double up. Or you could scrape some of the resist layer away to enlarge the pads. Remember, you're going to be hot-gluing over the wires to keep them in place (after soldering) so can afford to strip the insulation further back so it doesn't get in the way. Needless to say, you're going to need a powerful soldering iron (and remember to tin the stripped ends and pads first).

Don't know what that wire is going through the hole in the CF but wherever it's going to or coming from - it should have a sleeve or grommet. I saw a video on Youtube just the other day of a guy with a heli - a CF edge had cut through a power cable and started a fire. Carbon Fibre is conductive!
 

cbpagent72

Member
Like you I find the sparking on connection objectionable. So I just make the connection quickly and move on. Nothing I can do about it and apparently it's normal.

Just for some feedback from a fellow Droidworx flyer. I have a coax octo SkyJib. I use the Droidworx PDB being fed from two 6S 8Amp batteries. I've been using XT60 connectors for some time. They are tricky to solder to the larger wire but it's entirely possible and I am extremely careful to make sure these connections are solid. I believe that XT60 connectors can actually handle 80Amps but I don't remember where I read that. Nonetheless, I keep a careful eye on them and they never get warm and have never caused an issue.

Anderson was recommended to me by another Droidworx flyer after I had been flying for some time. If I had it to do all over again I certainly would use them instead as all this soldering is a pain in the butt and you have to be soooooo careful. But for now I have many batteries and devices all wired up solid with XT-60s so I won't be changing any time soon.

I went with EC5 connectors for my batteries and I have not noticed any sparks. The plugs are not as difficult to unplug as my xT60 connectors are either which is a huge positive for me.

Sent from my SPH-L720 using Tapatalk 2
 

Quinton

Active Member
You do make quite a lot of valid points Jes, but with the likes of bending the ESC wires 180 degrees, I cant see how it could possibly break or weaken any wires, is this not just a bit too much caution, as I am sure there are 100s if not 1000s of machines flying around today.
I do agree with where the wires come out of the CF holes from booms etc should probably be shielded, as a precauition but I'm sure again most people probably didn't do this.
I will be puttting liquid tape over my electrical connections, Im not sure if you had a bad solder if hot glue would help you much, but then again I don't know.

Putting something over the bullet connectors between the ESCs and the motors is a must, as the 3.5mm connectors aren't exactly the tightest of fits and I could see them working loose.
I have just bought a watt meter and a thrust meter to try and see exactly what sort of Amperage is being pulled (for my own benefit) just need to order up some more connectors to add it inline, will be interesting to see myself.
 

jes1111

Active Member
You do make quite a lot of valid points Jes, but with the likes of bending the ESC wires 180 degrees, I cant see how it could possibly break or weaken any wires, is this not just a bit too much caution, as I am sure there are 100s if not 1000s of machines flying around today.
I do agree with where the wires come out of the CF holes from booms etc should probably be shielded, as a precauition but I'm sure again most people probably didn't do this.
I will be puttting liquid tape over my electrical connections, Im not sure if you had a bad solder if hot glue would help you much, but then again I don't know.

Putting something over the bullet connectors between the ESCs and the motors is a must, as the 3.5mm connectors aren't exactly the tightest of fits and I could see them working loose.
I have just bought a watt meter and a thrust meter to try and see exactly what sort of Amperage is being pulled (for my own benefit) just need to order up some more connectors to add it inline, will be interesting to see myself.

You can certainly bend a wire 180 degrees - it's not the angle that's important but the radius of that bend. Remember that everything on the craft will be subjected to vibration - one of the two "killers" of electrical systems (the other being heat). Vibration and heat have a nasty habit of unerringly finding the weak point and spoiling your day.

Mmmm... is "most people don't do it that way" a useful indicator? If you really don't what to fall out of the sky (as I certainly don't) then it's taking care of these little details that add up to a more reliable machine. Such fastidiousness is not of my own invention - look at how full-size aircraft are built and wired. There are stringent and strict rules about how to do things - based, for the most part, on long experience of "what causes crashes". Aircraft designers and service technicians will know the Minimum Bend Radius (MBR) for an particular wire and they will stick to it. It would be "professional negligence" to skip cheap and simple techniques and procedures that could mean the difference between staying aloft and crashing catastrophically. Why we should we treat our flying machines any differently? Personally I don't subscribe to the "thousands of people..." line because many of them do have crashes and rarely do they properly investigate the cause. "Oh, my ESC burned out" is usually blamed on cheap, Chinese quality or "just bad luck" whereas it is equally probable that their soldering was bad, an unsupported solder joint broke internally, a wire was bent too tightly or the insulation cut through where it rubbed against a CF edge, etc.

Not trying to force anything on you, but your questions have opened some interesting areas.
 

Quinton

Active Member
Just wondering does anyone know what battery connectors the Kopterworx blokes are using in the EVO video at 28 seconds?
Also at 2 mins shows 58A on hover using 2x 5800mAh

http://vimeo.com/77081412



 
Last edited by a moderator:


Quinton

Active Member
Thank You, now the question is, these guys know more about flying Multirotors than most of us put together, (Kopterworx) and they sell hundreds if not thousands from their own store.
Why would they choose XT150s which are rated up to 250A?
They actually seem to have them on a lot of machines they fly.
 

jes1111

Active Member
I suspect for the same reason as you chose XT90s - the wires fit in the holes in the back :).

IMHO bullet connectors are the invention of the devil. They are conveniently compact for motor to ESC wires so long as you heat-shrink them together. I believe they are a poor connector for any other role on a multirotor because they suffer from a long list of designed-in problems. Encasing them in plastic sleeves creates more issues than it solves. They rely on friction to keep them together. The friction is provided by a combination of tolerance fit and spring tension, both of which suffer from variation in manufacture and wear through use - it's pot luck whether you'll ever achieve a perfect fit - they're either so tight you can't get the damn things apart or too loose to stay together. Vibration will always tend to separate them, never tighten them. As a piece of engineering they are a disaster.

Back to the "rating" thing - if your first priority is reliability (which it should be for a camera ship), then you should choose each flight-critical component carefully, balancing the other factors (size, cost and weight) without letting them compromise the primary aim. Putting 250A-rated connectors on 10AWG makes no sense since the wire will have melted long before the connector does. Therefore those big slugs of gold-plated brass are nothing more than dead weight. If you have batteries with 8AWG wires then you have little other choice if you stay within the RC retail world.
 

Top