Soldering 8 AWG aint fun

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Re: Soldering 8 AWG aint fun

Postby Aviator » Mon Apr 11, 2011 10:08 pm

RCModelReviews wrote:If you do a search on Google you'll find out a lot more than I can tell you here but basically crimping is good because there is nothing between the connector and the wire to increase the resistance and the physical act of crimping doesn't cause the same "stress risers" that soldering does.

If you think about it -- solder isn't a particularly good conductor of electricity (compared to copper) but in order to create a soldered joint there must be a layer of solder between the two parts being joined. This means that electrically, a soldered joint has a higher resistance than a well-crimped one. With crimping, the wire and the terminal are pressed so tightly together that there's no resistance other than the resistance of the wire and the terminal itself. While this might not matter for low-current connections -- the resistance of the solder can become an issue at very high currents.


http://www.allmeasures.com/Formulae/static/formulae/electrical_resistivity/30.htm

Voltage Drop.jpg
Voltage Drop.jpg (43.77 KiB) Viewed 1497 times


Out of curiosity I've done some calculations. Lets say a 3.5mm bullet has the soldering area 37mm² and the longest distance for the current to travel through the solder is 0.5mm - the resistance is 0.00000229Ω... Lets try to get a picture of what does that number mean. Lets check.. Wow, the resistance of a 3mm in diameter and 3mm long solid copper conductor is 0.0000072Ω! That is 3 times higher than our connection in question. Another interesting fact is - the internal resistance of a standard LiPo battery is 1000 times higher than our connection. We could have 1000 solder connections one after another and only then it will add up to the internal resistance of one regular LiPo!

If my motor at one point is drawing 30A, the voltage drop across the solder joint would be 0.000067V
If my circuit has 8 bullets with 8 solder connections at any given time, the total voltage drop would be 0.00054V
That is equal to a total power loss on all my solder connections around 0.0162W
If my circuit is producing 300W of power, the power loss percentage wise would be 0.0054%
That is 200 times less than 1%!

Is it enough to worry about? Not for me. I am losing thousand times more power inside of my battery, conductors, connectors and other things with funny names than in all my solder connections.

Interesting calculations and unexpected results.. (or have I made a mistake or two? :) )
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Re: Soldering 8 AWG aint fun

Postby Coverdown » Tue Apr 12, 2011 11:36 am

takilara wrote:Hmm those connectors look nice.
Can the entire range be used with crimping? They had connectors for 120 and 180A wich would suit me perfectly..


Yes , they can be be used with crimping, but the standard crimp tool only crimps Powerpole 15, 30 and 45 amp. Connectors.
These amp ratings are very conservative tho.

If you want crimp connectors above 45 amp rating you will need a bigger and presumably much more expensive tool.
http://www.andersonpower.com/products/a ... #powerpole

P.s. I do not have the powerpoles at the moment (xt60) but i`m switching to powerpoles, because they have a lot of useful features.
1. no soldering
2. no heat-shrinking
3. genderless, so easy to use battery's in series or parallel without special adapters
4. ability to lock multiple connectors together
5. self-cleaning
The only negative is that they are pretty large compared to some other connectors.
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Re: Soldering 8 AWG aint fun

Postby Kozmyk » Tue May 10, 2011 9:51 am

I use either one of these:
http://www.amazon.co.uk/Jack-Sealey-Soldering-Iron-100W/dp/B000R9Y0ZK
or a butane pencil torch for soldering bullets.

The bulky bit of the Sealey has plenty of reserve heat for soldering heavy cable.
for EC# bullets I find the butane torch method leaves no solder on the outside of the bullet, making it much easier to press into the housing.

A problem with soldering pistols is that the claimed power is often not sustainable for very long and it's easy to burn them out, unless your buying a name unit like a Weller.
Even then I'd prefer the old fashioned element type of iron.

Regarding connector conductivity, Wayne Giles posted some interesting findings here:
http://www.rcmf.co.uk/4um/index.php/topic,78751.msg915307.html#msg915307
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