Powering the Arduino GSM Shield from a 5V battery


I'm hoping to power my Arduino with the GSM shield at a location without power. I have a solar charging kit that includes a battery with a 5V/2A usb output. The challenge is that the GSM shield requires up to 1A, which is more than what the USB input on the Arduino allows for. However, if I power the Arduino from the 5.5x2.1mm plug to allow a higher current, the regulator will decrease the voltage down from 5V.

The solution I'm thinking of would be to instead connect the battery to the 5V and ground pins, bypassing the regulator. Since the battery should never exceed 5V, as far as I know, would this option be safe?


The limitation of powering the Arduino through the USB socket could be the ~500mA? polyfuse.
You can also put your 5volt supply, if you're sure it's 5volt!, straight on the 5volt pin of the Arduino.
That bypasses the fuse and the "on USB power" mosfets.
There is a small risk of frying the onboard regulator.
If you're worried about that, use a 1N4004 diode between 5volt and Vin, with the cathode/ring to Vin.
Are you sure your shield uses 1A. That must be from the Vin, because Arduino's 5volt line can't supply that.
Better post the exact items you're using.

If your solar power kit has an 5V output, other than the USB connector, you can connect this output to the GSM shield power connector. Take care to always connect the Arduino first (USB cable), before applying power to the GSM shield. Otherwise you may risk to damage the Arduino pins connected to the GSM shield. A diode from the GSM power connector to the Arduino Vcc may eliminate that risk, but see @Wawa about frying the onboard regulator.

Otherwise you can connect the GSM power input to pin 1 (xUSB) of the USB connector. This solution may not work if you connect the on-board USB connector to e.g. an PC, instead of your power supply, as required to download an sketch to the Arduino. Simple solution: unplug the GSM shield until done.

I really wonder why I couldn't find instructions on proper (intended) powering of both an Arduino and GSM shield together. Did I miss something?

Items I'm using:

This is what I found on the above website for the shield it says:

It is recommended that the board be powered with an external power supply that can provide between 700mA and 1000mA. Powering an Arduino and the GSM shield from a USB connection is not recommended, as USB cannot provide the required current for when the modem is in heavy use.

I'm going to look into using a diode between 5V and Vin. What does that accomplish exactly?

The diode bypasses the onboard 500mA fuse, and should withstand the maximum current drawn by the GSM shield (2A).

The diode bypasses the onboard 500mA fuse, and should withstand the maximum current drawn by the GSM shield (2A).


The diode effectively is across the in and out of the 5volt regulator.
It prevents backflow through the regulator.
Most regulators already have such a diode inbuild, but it's not clearly stated in the datasheets of the small regulators used on Arduinos.


I just had a look at the schematic diagram of this Sparkfun shield.
It uses an onboard low-dropout 3.8volt regulator, so in theory it can run from a 5volt rail.

If you use this shield, and you're sure your USB supply delivers 5volt!/2A, you can JOIN (wire, not diode) Vin and +5volt and connect your USB supply to that point.

Also possible now, but not wise, to power through the USB socket.
The >500mA current could trip the polyfuse and overheat the USB mosfets.