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I have found a lot of information that circles around what I'm looking for, but nothing that directly answers it. It is possible there is no right answer.

 
 
I am jealous of the Macbook MagSafe magnetic power connectors and plan to make my own. I will use these magnetic 2-pin pogo connectors with a standard laptop power adapter.

My initial plan was to clip the power adapter's wire 2" from the end, perform a lineman's splice, and solder the pogo connectors in the middle of the wire.

Assume the power adapter cable is stranded copper of an appropriate gauge. Splice will be done lineman style with solder on top and heat shrink tubing over that. The pogo connectors are rated for higher voltage and amperage than the power adapter.
My Concern: Will 20V/5A be too much for a simple soldering job? Will it overheat?

At what voltage/amperage does solder become unsafe and melt plastic/heat shrink tubing?
Is there an amount of current after which you should crimp instead of solder?

I want to know the general rule of thumb, if there is one.

 
 
I read that you must crimp in walls (110V), cars, and boats. Not much information on where to draw that line of safe/unsafe.
I want to make sure this is not a fire risk. Laptops are often plugged in and left unattended at home for long periods.

Thanks all!

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    \$\begingroup\$ The insulation will melt before the solder does so this should not really be a concern most of the time. 22AWG wire can carry 8A so you are fine. Crimping vs soldering is not for electrical reasons as much as mechanical reasons. (like vibration). \$\endgroup\$ – DKNguyen May 9 at 16:23
  • \$\begingroup\$ A solder joint might fail if a potent enough heat source is close to it. A (low voltage) connector which is designed to be low ohmic will not heat up at all due to P = I^2 * R (R = resistance of the connector, I = current). \$\endgroup\$ – Christian B. May 9 at 18:20
  • \$\begingroup\$ solder doesn't care about amps, it cares about temp. temp relates to amps via ohms. solder joints usually have lower resistance than crimps, and thus create less heat. \$\endgroup\$ – dandavis May 9 at 19:09
  • \$\begingroup\$ @dandavis Where did you read that solder joints usually have lower resistance than crimps? Solder has higher resistance than the both connector and the wire, and a crimp cold welds the two together without the need for the higher resistance solder. \$\endgroup\$ – DKNguyen May 9 at 19:27
  • \$\begingroup\$ @Toori've are you saying that a lineman's splice that's soldered-over has more resistance than a crimped-on pogo pin? i don't have any sources, but i find that very hard to believe. \$\endgroup\$ – dandavis May 9 at 19:33

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