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So, I recently bought a Rpi Pico and tried to make a Bluetooth remote control out from it.

What I did:

I used an HC-05 Bluetooth module (require 3.3V), 3 momentary button switch (powered from GPIO pin), and a laser emitter (rated 5V and powered by using the VBUS pin) to make the project.

The project worked fine but I seem to bump into an obstacle when I'm trying to power it remotely.

I tried to use two 18650 batteries rated at 2000mAh, 3.7 V (nominal) ~ 4.2 (full charge), 7.4Wh to power the Rpi Pico from the micro USB port.

Until yesterday, the Rpi Pico worked fine and it seems to be okay with the voltage.

However, that's not until I decided to fully charge both the 18650 batteries and connect them to the Rpi Pico again.

After I connected the fully charged batteries to Pico, something is starting to get wrong. My Bluetooth module's LED indicator isn't lighting up and the Pico isn't responding.

Out of curiosity, I measured the voltage in the circuit as around 3.94V as opposed it should have a 7 - 8 voltage. But just after I recorded down my findings, smoke started to come out from the Rpi Pico and the IC is like its about to explode.

TL;DR:

I tried to power Rpi Pico from two fully charged 18650 batteries at around 7 - 8V from the USB port. But unfortunately fried the board afterward.

Beginner mistake?

Sorry if I'm a complete idiot to think I can power it with such high voltage. (I'm fairly new to electronics) Is it true that I overvolted the Pico and thus fried it up?

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    Yes, that is what happened. The voltage regulator is almost certainly dead and other chips may have been taken with it. Feb 15 '21 at 16:22
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Max input on VSYS (pin 39) is 5.5V (range 1.8V to 5.5V)

VSYS is the main system input voltage, which can vary in the allowed range 1.8V to 5.5V, and is used by the on-board 2.1. Raspberry Pi Pico Pinout 8 Raspberry Pi Pico Datasheet SMPS to generate the 3.3V for the RP2040 and its GPIO.

From the Pico datasheet https://datasheets.raspberrypi.org/pico/pico-datasheet.pdf

You could use a step down voltage converter or buck converter to reduce 7-8V to 5V.

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