I'm working on my first Arduino project and this is my first post here. Thanks in advance for your help.
I have an MKR1000 board with a Seesaw I2C Soil Sensor. I have it set up to record moisture and temp to an Adafruit data feed. I have just been testing and developing using USB power at my desk, either directly from the laptop of from my USB hub. I also have used it recently connected to a 5v output Kindle USB charging block. All that worked just fine. Next step for my project is get it running off a battery. I went on Amazon and bought this battery . It seemed to have the right specs from what I've read, 3.7v, 2800mAh, built in protection circuit.
I also have read that the MKR1000 can charge a battery when both battery and USB are connected. But as soon as I plug both USB and battery into the board it immediately gets very hot near the USB connector. I have done this with two different power sources, the aforementioned Kindle charger and USB hub connected to my laptop. With the USB hub it got hot enough that after about 2 seconds the board started smoking. Luckily it does not appear to have done any damage, as the board looks and functions just fine.
Electrical circuitry is far from my forte, so I have no idea what caused this or how to remedy. My best guess is that the battery is causing the board to suddenly draw way more power than normal.
Am I correct that I should be able to have both USB and battery connected to charge the battery? Do I need an external charger for the battery? Could it be that the battery has bad protection circuitry?
Pics of the setup: