Properly soldering wire connections is the preferred method for a robust electrical system.

To make this process easier, use a Solder Sleeve! Preinstalled, and measured, solder with sealing rings covered with durable Kynar tubing. 

MATERIALS:

• INSULATION SLEEVE: Heat-shrinkable, radiation cross-linked modified polyolefin. Transparent clear.
• SOLDER PREFORM WITH FLUX: SOLDER: TYPE CD18 per ANSI/J-STD-006. FLUX: TYPE ROM1 per ANSI/J-STD-004.
• MELTABLE RINGS: Thermally stabilized thermoplastic.

APPLICATION:

• These controlled soldering devices are designed to splice tin-plated or bare copper stranded wires rated for at least +85C
• Heat Gun required for proper installation
• For enhanced sealing, use ES2000 x 50mm  

https://www.wloutdoors.com/copy-of-wlo-heat-shrink-e1-50-10-pcs.html