I have this weird issue. I'm currently hooking up a 6-pack of 18650 batteries in parallel. I'm currently hitting 3.8v using the whole pack at the connector (yes, I need to charge them up). If I hook up my 5 meters of LED strip to it, I get a voltage drop in the beginning, which is really weird! Here's how I've hooked it up:
The VIN on the ESP8266 board can receive a wide range of voltage, so it doesn't matter if it gets 3.3v or 5v. The batteries won't ever go below 3.5v, so I don't need to worry about that.
The VIN pin receives about 1.3v whereas the first LED receives the 3.8v. The terminal/connector that splits the cables is simply one of these connectors. So the battery pack has a male connector, that connects to the female, which simply has two cables running from it.
What on earth is wrong?