Completing the Solar Circle: Building a Small-to-Medium Off-Grid System
After learning the basics and diving into the technical theory behind voltage, current, and system design, I reached the final step in my solar journey applying all that knowledge into a working system that met my needs. I wasn’t aiming to go off-grid entirely. I didn’t need to power a fridge or cook with the sun. My objective was clear: use solar energy to reliably charge tool batteries, run lights, and keep USB-powered devices operational without drawing from the main grid. This blog shares how I put that into practice and what I learned along the way.
The Core Setup: Panel, Controller, Battery, Load
Every solar system needs four basic components:
Solar Panel – To capture the energy.
Charge Controller – To regulate and protect the system.
Battery Bank – To store usable energy.
Load – The actual devices you intend to run or charge.
I worked with 12V solar panels wired through PWM charge controllers, which were more than capable for my medium-demand use case. Panels were arranged both indoors (near sunny windows) and outdoors (angled to catch morning or afternoon sun). These fed into sealed lead-acid and lithium packs, where the energy was stored.
Wiring Safely: Matching Cable Size to Current Flow
At this stage, wiring became just as important as the panels themselves. I learned quickly that undersized cable leads to heat, loss, and inefficiency. For my tool charging setup, I used heavier gauge wire and proper crimp terminals to avoid voltage drop especially when drawing power through USB converters or multi-battery adapters.
My loads included:
12V battery chargers for tools
USB battery packs for field work
LED lighting strips in the workspace
A small inverter (only used occasionally for testing AC conversion)
Real-World Testing: Charging Power Tool Batteries
One of the most successful outcomes was using solar to charge my Ryobi and Bosch battery packs via compatible docks wired to the 12V DC outputs. Some docks allowed for native 12V charging; others required step-up or step-down converters. While charging times varied (depending on sunlight and panel wattage), a typical 2Ah pack took between 4 to 6 hours under steady sun using a 30W–60W panel. Key learning: If you're planning to charge multiple batteries or high-capacity units, parallel solar panels with matched voltage and higher amp output are essential. As I expanded the system—adding more panels, another controller, and additional USB charging points—I came to appreciate the importance of modular thinking. Instead of trying to centralise everything, I split the system into two: One system for daily charging tasks (lights, fans, USB tools). Another for heavier charging like drills or battery packs.This way, I could monitor each system’s draw, isolate faults, and maintain uptime without overloading.
Final Summary: What I’ve Learned
Here’s a quick breakdown of everything this three-part journey has covered:
Concept Practical Application Volts = Electrical pressure
Dictates system compatibility and device limits Amps = Flow rate
Determines charge speed and cable sizing
mAh / Ah = Capacity Defines how much energy you can store/use
Series Wiring Increases voltage; used when powering higher-voltage loads
Parallel Wiring Increases current; perfect for DC charging setups
AC vs DC, DC is direct and efficient for off-grid charging
Solar Charge Time Formula
Wh = V x Ah, Time = Wh / Panel Watts
Looking Ahead: The Future of Off-Grid Integration
This blog closes the loop on my first journey with small-to-medium solar systems. I now have reliable, renewable power running several of my workspaces charging tools, running lights, and reducing my dependency on the grid. But this isn’t the end. The final blog in this series will take things one step further. In that entry, I’ll be exploring how to build a fully mobile solar workstation compact, rechargeable, and deployable anywhere. It’s the logical next chapter, bridging everything I’ve learned into a field-ready, renewable toolkit. So Ladies and Gentlemen, until the next adventure... Take care.
Michael “Druid” Thomas
Lunacare Cymru | Media - Blog