Nano V3 and battery question

Problem: I hooked up a Nano V3 to a homemade lithium ion battery pack (2 5000mAh 18650 batteries in parallel with 3.7v PCB-voltage verified by voltage tester). Nano reacted with continuous swing sounds. The same reaction occured on another nano V3.

I changed the battery pack to a single 18650 lithium ion battery pack from TCSS. No problems.

What do you think is happening? I need longer battery life. Im running 4 LEDs and FOC and sound.

You're running 4 LEDs of what, exactly? DO these LEDs have resistors on them?

4 Red Crees with 1ohm 2watt resistors on all.

Running Reds at 1A needs at least a 1.2Ohm resistor. Considering your getting constant swings with your homemade pack, it sounds to me like you're pulling too much from your new battery pack.

Ok. Will correct. Thx!