Using power bank to power Arduino pro micro based project

Using Arduino General Electronics
1

Hi,

I'm building a project based on Arduino pro micro which has a 16X2 LCD and a few LED to power. I have an power bank of around 1500mAH as attached.. The battery shuts down automatically in few seconds as the the circuit draws less than 50mA of current. Can I take the power from red and black wires (marked with red arrows) and connect to the RAW pin ?

My concerns is whether it's hazardous for the circuit and people around (fire or explosion)

Thanks
Ran

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2

Don't try to connect anything to those wires, an accidental short could cause the battery to flame up or explode!
If you check the voltage on those wires, its probably only 3.7 to 4.2 volts, the power bank has a boost regulator built in to bring voltage up to 5 and also manage low current cutoff, if you put a 68 to 82 Ohm, 1/2 Watt resistor from Vcc to GND, will it stay on?
If so I built a simple transistor switch and timer once that pulsed the resistor on/off to keep the bank alive but not consume so much power as a permanent connection.

3

outsider:
Don't try to connect anything to those wires, an accidental short could cause the battery to flame up or explode!
If you check the voltage on those wires, its probably only 3.7 to 4.2 volts, the power bank has a boost regulator built in to bring voltage up to 5 and also manage low current cutoff, if you put a 68 to 82 Ohm, 1/2 Watt resistor from Vcc to GND, will it stay on?
If so I built a simple transistor switch and timer once that pulsed the resistor on/off to keep the bank alive but not consume so much power as a permanent connection.

Thanks for the reply..Now I realized that the battery output was 4.1ish even after full charge.. I will test it using a resistor to see if it stays or not. Meanwhile I came across https://www.dorkbotpdx.org/blog/paul/battery_pack_load which can also be built.

Thanks again!

4

There is a voltage regulator connected to the RAW pin. This voltage regulator has a dropout voltage so you need to supply ~6 V or higher to the RAW pin in order for the microcontroller to be running at the expected ~5 V.

Working with lithium batteries is a little tricky. You need to be sure not to over-discharge, over-charge, and over-current. Otherwise you could damage/degrade the battery or even start a fire. A protected lithium cell has a battery management system (BMS) that prevents all of those bad states. In the case of your battery, the BMS might be in the power bank rather than incorporated right onto the cell. So you definitely don't want to connect anything between the battery and the BMS. On the other side of the BMS, you can pretty much do as you like with it (electrically) without any danger. Of course you also need to be very careful to avoid mechanical damage to the battery.