DaveInDenver
Rising Sun Ham Guru
Just an fyi, but if this is your finished connection it looks like the solder never melted in your connectors.
You may not understand what he's talking about. It looks like you already hit your splices with a heat gun since the shrink is shrunk. But the solder didn't flow so the connection is electrically not done.I'm not done, don't have a good way to connect to the battery, so it's sitting unfinished right now.

You will see the outer shrink first but you have to hold the heat longer, enough time for the solder to flow.
View: https://www.youtube.com/watch?v=7Wh5gM8GM70