Crafted to give the best features for makers and hackers, any of the Raspberry Pi model A, B or B+ are microcomputers designed to be connected to high quality chargers with stable power delivery and able to provide an output of 5V with at least 700mAh.
As any other single board computer, the fruit-name board can be supplied with power from different sources. In this article, I explore three different solutions to power the board including the standard Mirco USB power supply, and continue with batteries and solar power.
Here comes the science
To choose the right power supply for a Raspberry Pi, you first needed to understand the recommends from the Raspberry Pi Foundation. The group of engineers that take part on the project makes the recommendation to use a Micro-USB power supply. More than that, the Micro-USB power source has to produce 1.2A (1,200mA) at 5V.
Let’s see why these values are just recommendations.
Why 5V and why 1.2A? The value of power consumption is directly proportional to the amount of power consumption of consumers connected to the board as well as features of the board. For example, at a standard level the Model A uses around 500mA, the B model uses between 700mA and 1,000mA, while the Model B+ was engineered with some improvements and has a 36% less power usage compared with the model B.
Why anyone has to keep in focus these values? The answer is simple and belongs to the laws of physics. If you connect to a Pi a lower power supply, for example connect a RPi Model B to a 550mA power supply, will cause strange behaviours to your single board computer. On the forums can be found strange behaviors for an inadequate power source including keyboards that repeat some letters even the users press a keyboard key once, or errors at startup from the SD memory card.
But, what about the upper bounds? It’s fine to use a power source with a high output current. Higher or equal to 1.2A. The problems appear when is applied excess voltage that can damage the circuits that doesn’t have sufficient protection provided by voltage regulators. Also, an excessive current rating is inefficient in operation and provide increased costs. For example, would be excessive to apply a 5A power supply to a Pi.
The best way to find the custom power supply for your project with Pi is to use a multimeter and read the voltage on the circuit board across two test points.
Let’s take a look at all possible power supplies for Raspberry Pi and then discuss in the comment section if something is missing or has to be adjusted.
The first option is also the recommended option as a power source for the fruit-name single board computer. Probably using a Micro USB charger is the best choice from both sides: the costs and the multitude of options. On the market are available at good quality different micro USB chargers including the mobile power supplies from major mobile operators around the world. The Micro USB is a standard charging port in the US, Europe, Asia, etc., and is very popular among Android, Windows or iOS devices.
The best option to choose a mobile phone charger is to look at the bottom of the charger and see the output values (may read 0.7mA or 0.7A), which is a cheap and good power source for Pi.
On the forums, I find projects where the designed uses different power supplies from mobile phones. Two of these are:
If you don’t have available at home one of these mobile phone power suppliers, you can buy a special power source designed to power the Pi boards. Below I have chosen for you three power sources with different adapters:
- UK Micro USB Raspberry Pi Power Supply – 5v 1500mA
- 5V 2A Ultra HQ USB Power Supply
- USA Raspberry Pi Micro USB Power Supply Charger – 5v 1500ma
If you’re using daily a laptop, inevitably you have moments when your laptop battery charge is at a minute distance to crush your creative session. But otherwise, the batteries make wonders.
If you have plans to use your Pi board in a no wire application, the best choice is to use a battery power supply to power your fruit-named board. In other words, you need to substitute a wall adapter power supply. There are a lot of options to power the Pi, eventually starting with the most common AA batteries. At a simple calculation, a Pi board can be powered by 4 x AA NiMh batteries able to supply an average of 1.25V.
Depending on how much equipment is connected to the Raspberry Pi, the board could draw between 0.5A and 1A. In this case a 4Ah battery can keep alive the board between 4 to 8 hours, while a 10Ah battery could supply with power between 10 to 20 hours.
Most common projects where the Pi makes a couple with a set of batteries are in drones. The Pi board is the ideal brain in UAV applications, but a heavy weight battery that takes hours could be a problem and increase the drain. This is the main reason that a quadcopter uses Li-Ion batteries designed for a high output. The disadvantage is that a higher output has a low duration, sometimes a drone can fly around 10-15 minutes.
If you don’t have inspiration, you can choose one of these sets of batteries:
- Team Orion 2700mAh AA 1.25V NiMH (4) ORI13502
- Gomadic Portable AA Battery Pack designed for the Raspberry Pi Board
Using solar panels to power the Raspberry Pi board is the third solution explored in this article. If you have plans to build your own solar power, I will give you some tips.
The main thing that you need to be aware is that the voltage output of a solar cell varies depending on the sunlight conditions. For example, a 12V solar panel battery charger can measure 18V in bright sunlight. A higher nominal voltage can do damage to directly connected electronics if is not used voltage regulators. The simple solution is to use a battery connected to the solar panel. Using a battery allows you to accumulate the excess of energy production and power the robot when the sunlight is low.
Using solar panels and batteries to power the Pi has a direct impact over the total weight of the drone. The best option to use solar panels in a UAV is to calculate the average power generation, the battery capacity, and the total expected power load.
A list with solar panel charges that can be used as power supply for Pi.
How Much Less Power does the Raspberry Pi B+ use than the old model B?, Raspi;
Solar Powered Raspberry Pi, Instructables;
What do I need to know to power from batteries?, Stackexchange;
Running a Raspberry Pi from 6 AA Batteries, Raspberrypi-Spy;