Greening Urban Environments

Guidelines - Project Three

Portable Solar Power System

Guidelines - Project Three

Portable Solar Power System

The objective of this project was to produce a simple small portable solar power system which can be used to independently power and control all sorts of small electronic devices (at USB 5 volts - e.g. ESP32, 5v or 3.3v relays, LED lights, irrigation valves) or other devices at 12 volts. A solar regulator takes the output from a solar panel to control the charging of a battery, but also provides the 5 volt and a 12 volt output for powering a range of useful GutterGrowing devices.

Currently this unit is being used to provide independent power for the ESP32 microcontroller and a range of sensors which check the operation of a GutterGrowing system and provide data and control messages (or warning messages to a mobile phone if a problem occurs).

The solar power unit packs into an easily carriable waterproof container so that it can be moved to any location where small amounts of 5 volt and 12 volt power are required.

What you need:

  1. Small 12v solar panel (10w or more)

  2. Small 12v sealed rechargable battery (now best to use LiFePO4)

  3. Solar regulator with 12v and 5v (USB type) output

  4. Waterproof carry container with lid


The following details are provided as GUIDELINES ONLY. There are vast ranges of all the components needed for this project and the choices will depend on individual requirements. The illustrations provided are for a working experimental system we have under test and are not intended to be prescriptive. Individuals MUST ensure that their choice of components fit together and are compatible with each other.

The choice of physical size of the container and solar panel is very much an individual choice. Vendors of solar panels and controllers will be able to advise on suitability and compatibility with various sizes of battery. Vendors will also be able to provide connection wireing suitable for your choice of components.

Step 1 Choose a small solar panel and a waterproof container

There are many options on the market for the choice of a small solar panel - the one shown here is a 10 watt solar panel which measures 38cm x 25cm. There are also many options for choice of waterproof containers - the one shown here is a 25 litre plastic storage box from Wilco which measures 32x40x25 cm. It has moulded in carry handles (useful) with a ridged top surface in the handle area (very useful for guiding power leads running out of the system). It has a transparent lid which when in position retains, and keeps dry, all the components.

It is important to check the dimensions of all the components to ensure they fit into the closed container. Our 10watt panel costs around £20-£30 and the container another £5

solar panel battery solar controller

Step 2 Choose a small 12v rechargable battery

Typically a small 12v sealed LiFePO4 rechargable battery will be the best choice. The one shown here is a Eco-Worthy 7Ah 12v LiFePO4 rechargable battery (cost £32-£34).

Step 3 Choose a 12v solar battery charge controller with 5v and 12v outputs

solar controller

Our chosen controller has a display which shows the battery voltage. The connection points along the bottom provide connections to the solar panel and to the battery. Usually it is important to connect to the battery first and then secondly to the solar panel. Down the right side there are two USB output connectors providing 5v and two output connectors providing 12v (cost around £15 - this one was from Amazon).

We have been using it to run an ESP32 microcontroller and relays (at USB level of 5v) which control 12v irrigation valves (details coming soon) . It also runs a music player which cheers everyone up when we hear what Donald Trump is up to.

system in boxsystem in portable boxperson carrying solar system

The whole system packs into easy to carry containers so that you can site it or move it to any convenient space. The solar panel is waterproof and so it can be used (for very limited solar capture) in the container - or more normally outside the container where it can be situated to maximise solar capture. Our experimenetal system has been running our microcontroller and relay to control the irrigation of our 'guttergrow' system during the summer months. The ESP32 has both wifi and Bluetooth to facilitate internet connections.

Return to projects menu