Saturday, February 23, 2013

Heavy Duty Connectors and Large Gauge Wire, & XT60 Soldering Experiment


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By Gabriel Staples
Written: 22 Feb. 2013
Last Updated: 2 March 2014
-added links to full soldering tutorials

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So, tonight I decided to do an experiment to see how large of wire could be used with my favorite connector, the genuine XT60, from HobbyKing.  Ultimately, I determined that a careful hand and hot iron (60W recommended, as my "Beginner RC Airplane Setup" document explains here) can easily handle wires at least up to 7 AWG, which is a very large diameter wire.  In my experiment, I twisted two 12AWG wires together, to make a 7~8 AWG-equivalent wire, which I then soldered to an XT60 connector with no problem.  A smaller diameter wire, such as a 10 AWG, can easily be soldered to an XT60 connector with this iron linked above (as this is the exact iron I used).  However, as 10AWG wire is capable of carrying currents much greater than 60A, you may be interested in using the larger XT90 connector, on which 10 AWG wire comes standard on a HobbyKing XT90 parallel harness or serial harness.

Various Large-Current, Large-Diameter-Wire Connector Descriptions, & Links:
XT60-style connectors are my favorite, hands down, for my personal use.  The 60 means "60 Amps," so as long as your *continuous* current is 60A or less, use these connectors, with any wire up to about 7 Gauge or so (though 14AWG wire is large enough to do the trick).  Anyway, for 60A or less continuous, or ~100A peak (<=30 sec), XT60's are the way to go.  For 90A continuous, or ~140A peak, use XT90's.  For 150A continuous (250A peak), use XT150's.  Also, as a side note, 10 AWG wire is designed to easily handle a high voltage 90A continuous current over short distances (you can verify using this online calculator here, with values of 1% loss, 22.2V DC, 90A, and 0.3m cable length), but again, if your system pulls <60A continuous, feel free to use XT60's, even for wire such as 10 AWG or as large as 7AWG. 

My Soldering Experiment on the XT60 Connector:
-My goal was to see if large gauge wire (10AWG or larger) could be soldered to the XT60 connector, in order to use this connector to replace other large, bulky, or cumbersome connectors on very large battery packs where you need less than 60A continuous current draw.  (Note: if you ever replace battery connectors, be very careful not to short out the battery leads by cutting off both wires on the battery connector at once.  Rather, cut off and solder one wire at a time to a new connector).
-Results: I successfully soldered the equivalent of 7AWG wires onto an XT60 connector.  I did not try to solder wires any larger, as this was large enough for the purposes of my experiment.

-This entire experiment, including taking the photos, took me 20 minutes, and 30 seconds.  I timed it, from the time I cut the first wire to the time I finished heat shrinking the last piece of heat shrink covering.   

Since I didn't have any 10AWG wire (my largest wire I have is 12AWG), I first cut a piece of 12AWG high-strand count, very high-quality silver-coated, silicone-cased audio cable.  You can see the gauge printed on the wire.   

Next, I stripped the covering off of *both* strands of high-quality 12AWG wire, and twisted them together to make one big strand of wire.  I measured this large single strand, made up of two 12AWG wire strands twisted together, and found that its diameter was 3.13mm, or almost as large as an 8AWG wire (see here for a table of AWG wire sizes and diameters; an 8AWG wire has a diameter of 3.264mm).  

I then tinned the end of this wire, and the solder increased the thickness to 3.75mm, or ~7AWG equivalent.

I then cut another wire, this time a low quality, low-strand-count copper audio cable, stripped the covering off of *both* strands of wire, twisted the two 12AWG strands together, and measured the diameter.  Since this lower quality wire was slightly thicker, the combined strands measured 3.60mm diameter, or 7AWG equivalent.

After tinning this wire, its diameter was 4.48mm, or nearly 5AWG equivalent.

Next, I carefully tinned the two golden terminals on the XT60 connector, leaving an ample pool of solder in the recess of each terminal in order to wick into the tinned wires upon soldering, making the joining process easier.  I then soldered the two sets of tinned wires to those terminals, one at a time.  

The below three pictures show the high-strand-count wires (blue casing; 8AWG wire equivalent when untinned) and the low-strand-count wires (copper, with clear casing,; 7AWG wire equivalent when untinned), soldered to the XT60 connector.  The 60W iron worked extremely well and easily tinned the large wires, and did this soldering job with minimal effort and only a few seconds of contact at a time on the wires or connector terminals.  The solder joint was very solid, firm, and strong, and I would feel confident yanking on these wires all day long without them coming loose.  

Finally, I placed a piece of 6mm black heat shrink tubing over the two 12AWG negative wires, and a piece of 10mm red heat shrink tubing over the two 12AWG positive wires.  The positive wires required larger heat shrink tubing since the nicer blue silicone casing was thicker than the cheap plastic casing on the other wires. As a final touch, I used a small piece of 14mm black heat shrink tubing over the edge of the XT60 connector itself.  Voila!  All done, no problems, 7AWG equivalent wire successfully soldered to an XT60 connector with no problems whatsoever.  NOTE: IF YOU TRY THIS WITH A 30W SOLDERING IRON, I THINK YOU WILL HAVE PROBLEMS.  You'll probably have a very difficult time getting good heat transfer, and will have to hold the heat on for a very long period of time, likely melting the nylon XT60 connector, and perhaps getting frustrated and angry. :)

Here is a final picture of all of my soldering equipment I used.  

Full Soldering Tutorials:

My article above is not a true soldering tutorial in any way, rather, it is simply a proof-of-concept demonstration that you can in fact hook up some very heavy gauge wire to a HobbyKing XT60 connector.  If you would like a true soldering tutorial, I recommend the following:
  1. Sparkfun's "How to Solder - Through-hole Soldering" Article - the two videos here are definitely worth watching too!  Very good information!
  2. Adafruit Guide To Excellent Soldering - this is another fabulous soldering tutorial, with lots of great pictures, tips, & tricks!
The above two tutorials, when used together, are an absolutely fantastic reference and guide, and I very highly recommend you check them out.  Also, don't forget to browse my blog and see what other articles I've written that may be interesting to you.  See the links to the top-right, and don't forget to click the envelope icon to subscribe by email.  Thanks, and happy days!




The below pictures are in answer to Scott's post below.  I am showing the tinning compound, and my tinned, worn-out, soldering iron tip.

Here is the tip tinner and cleaner from Radio Shack, lying next to a brand new soldering tip, lying next to my 60W soldering iron.  To use the tip tinner, just heat your soldering iron and roll your tip in it.  The soldering iron originally had a nice new tip just like that in it.  Now, it's all chewed up, as I have no temperature control on the iron, so it gets hotter than necessary and slowly melts itself away as I solder.  The tip is about 2 years old and has been used on *many* many jobs.  Notice the black crusty stuff all around the base of my soldering iron tip. That's heavy oxidation.

Here, notice the silver area on my solder tip.  That's a nicely tinned area of the tip.  Since the iron is cool, it is  a dull silver.  However, if I were to heat the iron and clean the tip on a wet sponge, that dull silver area would be a very shiny silver area, which is indicative of a nicely tinned area.   

Side view, again showing the tinned part of the tip.

Back view, showing only oxidized areas of the tip.

Another view, showing some more of the tinned part of the tip.

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  1. interesting article. I nearly ruined a brand new battery and XT60 connector tonight trying (for the first time) to do this with simple 12AWG wire. I used a new 40W iron with a pointed tip which despite transfering plenty of heat through the plastic handle to make it painful to hold the stupid thing, could barely melt the solder when I held it to the iron. It seemed like the tip was filthy simply from touching it to the solder. Yes - it took a long time to transfer heat to the connectors and the plastic sizzled a bit just trying to fill the little pots with tin. Thus, I had no recesses into which to push the heat shrink, so I just had to push them as far down as possible to avoid any bare wire. I think I'll do like you and get a larger piece of heat shrink to cover the whole connector. You should mention for others that if you are soldering a connector to something that has wires already attached (ex. wiring harness or battery) the heat shrink needs to be placed on the wire (slid back) BEFORE you begin soldering, then moved into place and shrunk - obvious, but easy to forget.
    thanks for the tips - oh, speaking of which, what tip did you use on your iron?

    1. How'd you nearly ruin your battery? Short circuit? Too much heat? (likely from poorly tinned tip requiring too much contact time)

  2. Scott, sounds like your solder tip is badly oxidized. An oxidation layer acts as an insulator and prevents good heat transfer. Clean the heated tip on a wet sponge and see if the tip (or any parts of it) is/are bright shiny silver. Bright shiny silver parts are properly tinned, but dull areas are oxidized. With my 60W iron it only takes a couple seconds to melt all the solder I need into the connector recesses, and only a few seconds to tin the large wires, since the tip is nicely tinned. If you've ever heated up your iron, even for only a few seconds, even once, without holding solder to it *as you heated it* for the *very first time* the tip was used, it's likely oxidized. To fix this, take an X-acto knife and scrape against the hot tip. It should get shiny immediately then rapidly begin to dull. Put solder against the shiny area the second it is cleaned and shiny. Repeat this process of scraping and applying solder to the tip until the tip has a nicely tinned area. A properly tinned tip will also easily hold solder, whereas an oxidized tip will cause the solder to bead up and fall off of it. Now, that's the hard way; an easier way is to use tinning compound. Buy some tinning compound (ex: Radio Shack model 64-020: and roll your *heated* soldering iron tip into it. It will instantly be tinned. Once a soldering iron tip is properly tinned, it never has to be tinned again. Simply maintain the tinned tip by periodically cleaning the hot tip on a wet sponge just before each soldering touch/job, and leave a little solder on the tip just before cooling and storing it.

    Having a nicely tinned tip means you can quickly transfer the necessary heat to the metal part of the connector *for only a few seconds*, thereby keeping the nylon part relatively cool so it doesn't melt. Also, a good solder joint will be very shiny, as the pictures above show. It is very strong. A poor joint, or "cold solder joint" will be dull and easily break, come loose, or fracture. If your joint is cold it means you didn't have enough heat, or flux, or both.

    As for the soldering tip, for large jobs where good heat transfer is necessary, I prefer a spade tip (flattened), as it is larger and has more heat transfer area. However, this isn't really important. I'll post some more pictures above and you'll see my soldering iron tip is chewed to nothing, as I've used the same tip for 2 years and am using a $7 iron, with no temperature control, so the tip gets hotter than necessary and slowly melts itself up as I solder.


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~Sincerely, Gabriel Staples.

P.S. Yo hablo español también. Je parle français aussi. (I speak Spanish & French too).