How do you splice a micro USB cable to a USB cable?

Question

I'm making a "heated vest" Christmas gift for my wife by adding heating elements to a "fashionable" vest. I've done this for others in the past:

1. Velcroed in this tiny power bank
2. Micro USB to USB adapter
3. Plugged into these heating pads which are sewn into the vest

The adapter (step 2) is bulky, so this time I:

1. verified it was working
2. severed the Micro USB cable and the USB cable
3. both cables have only two wires, so I soldered them together
4. it doesn't work :(

The USB has white and black wires. Micro USB has red and black. Initially I tried white-to-red, black-to-black. Didn't work. Switched them. Still didn't work. Bought a new battery & new cable, spliced them again - no luck. Both batteries were fully charged.

Is there some magic happening in the adapter that I could be missing? Any bright ideas?

Answer 1

Figure 1. The solder has not wet the coated copper wire.

You haven't applied enough heat to melt the varnish coating on the copper coloured wire so you have no connection.

You need to either increase the temperature significantly or scrape the insulation off with some very find sand paper.

There may be other problems but I'd start here. Use a voltmeter to check for voltage at various points along the way.