Large spark from XT90 connectors

[Quinton]

First time using 6S lipos, (6200 mAh) and in the middle of a Skyjib 6 build.
Whenever I connect the lipo to the XT90 connector there is quite a large spark.

It looks like it would damage the connectors over time (not to mention other electronic stuff)
Any help would be appreciated.

 

[Bartman]

First time using 6S lipos, (6200 mAh) and in the middle of a Skyjib 6 build.
Whenever I connect the lipo to the XT90 connector there is quite a large spark.

It looks like it would damage the connectors over time (not to mention other electronic stuff)
Any help would be appreciated.

Quinton, the sparking is normal. THe motor controllers have large capacitors which act as reservoirs for electricity. WHen there is a large and sudden demand for electricity, the batteries get a little help from the charge stored in the capacitors and when the batteries get caught up the capacitors get recharged.

When you first plug in the batteries the charge in the capacitors is zero and so there is a rush of electricity as they quickly go to full charge. The spark is from this virtually unlimited flow of electricity. One way to minimize the spark is to lean the positive side of the connectors together before pushing the connectors together. BY doing this the spark happens on the negative poles of the connectors and the spark will be lessened as the current has to flow through the capacitors and the rest of the circuitry before getting to where the contact is being made.

Hope that helps,
Bart

 

[Quinton]

Thanks for the reply Bart

I was worried, as you can start to see burn marks on the XT90 Connectors, and thought over time this could be a problem.
I was scouring the net looking for other posts regarding this, but there was not much around but did come across the following Jet Anto Spark connectors which come in 4mm 5.5 and 8mm

You can see a video of them here..
http://youtu.be/yEQC7YPj0m0

Just wondering if these could be put in the lipo lead to stop the arcing, or would this be a bad idea?

 

[Bartman]

it's not an uncommon things in RC electrics to use different tricks to stop the sparking but it also isn't uncommon to just plug away. the damage, even after a couple of years doesn't amount to much so I haven't used any products/tricks to stop it. try the technique i mentioned above where the positive poles are made to touch before the negative poles. the spark will be smaller and you might be happy with that.

bart

 

[Quinton]

it's not an uncommon things in RC electrics to use different tricks to stop the sparking but it also isn't uncommon to just plug away. the damage, even after a couple of years doesn't amount to much so I haven't used any products/tricks to stop it. try the technique i mentioned above where the positive poles are made to touch before the negative poles. the spark will be smaller and you might be happy with that.

bart

Indeed your right, the spark is about half that of normal

 

[FlyGirl]

Quinton, the sparking is normal. THe motor controllers have large capacitors which act as reservoirs for electricity. WHen there is a large and sudden demand for electricity, the batteries get a little help from the charge stored in the capacitors and when the batteries get caught up the capacitors get recharged.

When you first plug in the batteries the charge in the capacitors is zero and so there is a rush of electricity as they quickly go to full charge. The spark is from this virtually unlimited flow of electricity. One way to minimize the spark is to lean the positive side of the connectors together before pushing the connectors together. BY doing this the spark happens on the negative poles of the connectors and the spark will be lessened as the current has to flow through the capacitors and the rest of the circuitry before getting to where the contact is being made.

Hope that helps,
Bart

That's a good tip Bart! Thanks! The 4s sparks are enough for me... The 6s spark must be a humdinger!

 

[jes1111]

As a matter of interest, why do you need XT90 connectors on your rig? Their (claimed) rating of "90A and beyond" (!) exceeds the safe rating for 10AWG wire. If you're going to pull that sort of current on a camera ship then you should be wiring to a bus bar (of some sort) so no single wire/connector has to take that sort of strain.

Incidentally, one of the (many) advantages of Anderson Powerpole connectors is that any arcing that does occur will be located at the tips of the "blades" which are not subsequently part of the contact path between mated connectors.

 

[Quinton]

As a matter of interest, why do you need XT90 connectors on your rig? Their (claimed) rating of "90A and beyond" (!) exceeds the safe rating for 10AWG wire. If you're going to pull that sort of current on a camera ship then you should be wiring to a bus bar (of some sort) so no single wire/connector has to take that sort of strain.

Incidentally, one of the (many) advantages of Anderson Powerpole connectors is that any arcing that does occur will be located at the tips of the "blades" which are not subsequently part of the contact path between mated connectors.

Im quite new to this and I am going on the advice of my dealer who puts together quite a lot of these so I had no reason to disagree, not to mention Id never get the 6S Lipos to fit into an xt60.
I am doing a lot of digging around and learning however, as I usually "need to know why" certain things are/are not used, and during my latest web investigations came across that 10AWG is rated for up to 140A but I am no expert, I am just trying to gather as much info from others as I can so if anyone else has anything to say regarding this I am all ears.

 

[jes1111]

Didn't mean to imply that XT90s were a wrong choice, per se - just fishing inner detail on the build. A primary aim with a heavy camera should obviously be reliability - the entire drive train from battery to motor should be "de-rated", i.e. nothing should be stressed to more than about 50% of its rated capability. For example, 10AWG wire may well safely handle 140A for a few seconds, but asking it to do so (in the context of a camera ship) represents an unnecessary risk. In fact the real "rating" for 10AWG is about 60A, btw. There are ways of arranging the wiring between batteries and ESCs that would keep everything within a sensible de-rated range. One of the most obvious factors is the choice of battery packs - several smaller capacity packs run in parallel is better than a single pack of the same total capacity (in which the entire load will be carried by a single wire/connector path).

 

[Quinton]

That is actually interesting to hear, and I would love to research more on the subject.
I suppose it also depends on the type and size of the wire 10AWG being approx 5.5MM, and if its made out of Aluminium, Copper or other material.

May I ask where you got the 60A real rating for 10 AWG from, I just like to find out factual information and am interested on reading up on it.
The information I am working from comes from the attached file.

View attachment 14143

 

[Quinton]

One of the most obvious factors is the choice of battery packs - several smaller capacity packs run in parallel is better than a single pack of the same total capacity (in which the entire load will be carried by a single wire/connector path).

That's also something I am interested in finding out, but also to take into consideration is the weight of the battery packs.

Example all 35C..

4600 Mah 6s 22.2V being 672g (£75) approx
5200 Mah 6s 22.2V being 736g (£86) "
6200 Mah 6s 22.2V being 883g (£100)
8300 Mah 6s 22.2V being 1115g (£150)
10400 Mah 6s 22.2V being 1591g (£180)

So need to work out what would be the best setup for longer flight time/weight/price/anything else I am learning about.
There's a calculation theory in there somewhere also taking into account the extra wiring weight.

Don't worry about the ramblings below, Im just posting this for my own future reference.
Ok not taking into account flight time, the 8300 mAh seems to be the best value for £/weight/power ratio..

6.8 mAh/g
7.06 mAh/g
7.02 mAh/g
7.44 mAh/g
6.53 mAh/g

61.3p / mAh
60.5p / mAh
62p / mAh
55.3p / mAh
57.7p / mAh

 

[jes1111]

AMR (in that chart) stands for Absolute Maximum Rating - enough said!

10AWG is the "size" of the wire. We're only dealing with copper here (aluminium wire is another whole ballgame). The rating is related to the allowable (or sensible) temperature gain (above ambient) as well as the ventilation, the thickness and material of the insulation, etc. Silicone insulation is used in this application because it can (theoretically) withstand up to 200 degrees Celsius - but you'd be mad to "allow" a temperature gain of more than 40/50-ish degrees above ambient (for the wire or the connector).

Same goes for sparking IMO - I wouldn't "allow it" at all, since it does deteriorate the mating surfaces of these hobby-type connectors, increasing resistance and therefore exacerbating the heat gain problem.

 

[Quinton]

Same goes for sparking IMO - I wouldn't "allow it" at all, since it does deteriorate the mating surfaces of these hobby-type connectors, increasing resistance and therefore exacerbating the heat gain problem.

See you walked right into that one
I'm here to learn and to share with others, how do you not "allow it"!

 

[jes1111]

See you walked right into that one
I'm here to learn and to share with others, how do you not "allow it"!

in my rigs, by using Anderson Powerpole connectors - they arc, but not in the place where the blades press together once fully mated. This is one of the differences between using "real" industrial/military high-current DC connectors and hobby items designed to attract your money. As another example of the difference, look at the universal belief in the RC world that gold-plated connectors are "the best". The Powerpole contacts are silver plated because a) silver has lower resistance than gold and b) its oxides are equally conductive. But gold plating looks "flashy" so that's what the vendors want us to believe is better.

If I didn't have Powerpoles I'd go with a regular "resistor in a wire" setup. The anti-spark device you linked looks like it works - but it's pricey and it's the whole connector, i.e. you can't retrofit it to any other connector. In general I don't rate connectors that can't be positively locked together (as Powerpoles can) - and I choose crimped connections over soldered, for reliability reasons.

Oddly this is a very contentious subject in the RC world - your choice of connectors (and soldered vs. crimped) seems to raise more heated "discussions" than any other component

 

[jes1111]

That's also something I am interested in finding out, but also to take into consideration is the weight of the battery packs.

Example all 35C..

4600 Mah 6s 22.2V being 672g (£75) approx
5200 Mah 6s 22.2V being 736g (£86) "
6200 Mah 6s 22.2V being 883g (£100)
8300 Mah 6s 22.2V being 1115g (£150)
10400 Mah 6s 22.2V being 1591g (£180)

So need to work out what would be the best setup for longer flight time/weight/price/anything else I am learning about.
There's a calculation theory in there somewhere also taking into account the extra wiring weight.

Don't worry about the ramblings below, Im just posting this for my own future reference.
Ok not taking into account flight time, the 8300 mAh seems to be the best value for £/weight/power ratio..

6.8 mAh/g
7.06 mAh/g
7.02 mAh/g
7.44 mAh/g
6.53 mAh/g

61.3p / mAh
60.5p / mAh
62p / mAh
55.3p / mAh
57.7p / mAh

If you make cost the driving factor then it's going to be at the expense of reliability...

Start your calculation at the other end - what the power requirements of the motors will be - calculate the amperage involved, work back to the battery to make sure everything else in the chain can handle the load safely and reliably.

 

[Bartman]

...........Anderson Powerpole connectors - they arc, but not in the place where the blades press together once fully mated.

how many do? Deans, no. XT-60, no. EC-3, no. they all make contact on the sides away from where the arcing occurs and if connected properly the arcing is minimal.

Anderson's are bulky by comparison, and expensive. The thousands (hundreds of thousands?) of connectors out there in use are enough to ensure their reliability and utility.

here we go again. compulsive connectors commentary, gotta love it.

 

[Quinton]

in my rigs, by using Anderson Powerpole connectors - they arc, but not in the place where the blades press together once fully mated. This is one of the differences between using "real" industrial/military high-current DC connectors and hobby items designed to attract your money. As another example of the difference, look at the universal belief in the RC world that gold-plated connectors are "the best". The Powerpole contacts are silver plated because a) silver has lower resistance than gold and b) its oxides are equally conductive. But gold plating looks "flashy" so that's what the vendors want us to believe is better.

If I didn't have Powerpoles I'd go with a regular "resistor in a wire" setup. The anti-spark device you linked looks like it works - but it's pricey and it's the whole connector, i.e. you can't retrofit it to any other connector. In general I don't rate connectors that can't be positively locked together (as Powerpoles can) - and I choose crimped connections over soldered, for reliability reasons.

Oddly this is a very contentious subject in the RC world - your choice of connectors (and soldered vs. crimped) seems to raise more heated "discussions" than any other component

I just watched this video on Anderson Power Connectors, and could be sold on them before I start going in too deep into getting dragged into the XT60/90 and bullet connectors for chargers/lipos/motors escs etc.

http://youtu.be/y8ODI8fAU_k

So far I dont see any down side, no need to solder the connectors are dirt cheap and they take seconds to connect, however he mentioned the maximum was 45A for AWG 10, would that not be a bit low?

 

[Scott Drysdale]

In North America the voltage and current ratings of each conductor size are listed the National Electrical Code, i.e., NEC (USA) and CEC (Canada). There will be other agencies for other countries and perhaps IEC - International Electrotechnical Commission. The conductor material and diameter determines the amount of current the wire can handle. Copper is the most practical conductor material choice. The voltage rating of a cable, i.e., wire encased in protective insulation, defines the wire insulation capability, i.e., a 600 volt rated cable has insulation designed to handle 600Volt without insulation breakdown. BTW - Never use aluminum wire for connections to equipment prone to vibration such as motors.

That is actually interesting to hear, and I would love to research more on the subject.
I suppose it also depends on the type and size of the wire 10AWG being approx 5.5MM, and if its made out of Aluminium, Copper or other material.

May I ask where you got the 60A real rating for 10 AWG from, I just like to find out factual information and am interested on reading up on it.
The information I am working from comes from the attached file.

View attachment 17811

 

[Quinton]

Anderson's are bulky by comparison, and expensive.

They aren't too expensive here if these are the same things then only 56p each?..
http://uk.farnell.com/jsp/displayProduct.jsp?sku=2102001

I love to hear what people use, and the pros/cons for each, especially as I am just starting out and can afford to make the best choice.

-------

Ok an update on that, I have just watched another on installing on 10 AWG and it doesn't look as straight forward, requires another expensive tool and seems quite bulky.
http://youtu.be/5l31i571S6Q

 

[jes1111]

I just watched this video on Anderson Power Connectors, and could be sold on them before I start going in too deep into getting dragged into the XT60/90 and bullet connectors for chargers/lipos/motors escs etc.

http://youtu.be/y8ODI8fAU_k

So far I dont see any down side, no need to solder the connectors are dirt cheap and they take seconds to connect, however he mentioned the maximum was 45A for AWG 10, would that not be a bit low?

The "45A" label is misleading - it's there because that's the official NEC/CEC rating of 10AWG wire (which is for domestic installation in an unventilated conduit, etc. etc.). The reality (for our application) is that the connector can take whatever the wire can take and 10AWG is the largest wire that will fit inside the Powerpole, i.e. a "45A" Powerpole matches the ampacity of 10AWG wire, which is more than 45A (in our application). User reports of "45A" Powerpoles easily handling 100A are easy to find in RCG, etc.

A lot of people complain that the crimp tool (a necessity when using Powerpoles - they can be soldered but you lose half of the advantages) is too expensive. That's a personal choice but I never begrudge (reasonable) money spent on tools that the make the job easier and/or better.

how many do? Deans, no. XT-60, no. EC-3, no. they all make contact on the sides away from where the arcing occurs and if connected properly the arcing is minimal.

Anderson's are bulky by comparison, and expensive. The thousands (hundreds of thousands?) of connectors out there in use are enough to ensure their reliability and utility.

here we go again. compulsive connectors commentary, gotta love it.

See what I mean, Quinton? Hackles rise so easily on this subject - very odd. Not trying here to "push" Powerpoles on anybody or persuade anyone away from their personal choice. This thread started about arcing and I just thought I'd mention the Anderson's designed-in tolerance to that problem. Since you've expressed an interest in Powerpoles I'll continue, in spite of the personal risk

Powerpoles are, as you've found, way cheaper than any of the "pack of 3" RC connectors. They are not bulkier (even if that was a problem on a Cinestar, which it isn't) when you include the stiffening of the wire usually caused by soldering and the heat-shrink required to protect/support a soldered joint.

If I dare mention the crimp vs. solder issue (for fear of being jumped on by the pro-solder brigade :black_eyed - for aircraft, trains, military gear, etc. crimped connectors are the de facto standard - because they're easier and faster to make, they allow positive visual verification of a sound joint before final assembly of the connector, do not require the additional mechanical support/protection that solder connections do and have a lower resistance than an equivalent soldered connection. Powerpoles can also be positively locked together to remove completely any risk of in-flight separation due to vibration - another standard practice in aircraft, trains, military gear, etc.

Looked at the other way, if Deans, XT60s or whatevers are so great and reliable as high-current DC connectors, how come they are never used anywhere outside the RC world?