Well, simply put, electronic loads are the reverse of power supplies. They are test instruments that simulate loads on a power source by drawing a controlled amount of current or power. In their simplest form, they function like a large resistor, electronically controlled to pass a specific amount of power. However, there’s much more to them than just that.
They are used in many applications. Personally, I use them for battery testing to measure capacity, determine discharge rates, and perform lifecycle testing with controlled loads. This helps ascertain how many charge cycles a battery can endure. They are also used for lifecycle testing of power supplies and stress testing to check if they can handle specific power outputs.
A quality electronic load tester offers various modes. The Constant Voltage (CV) mode fixes the voltage regardless of the current, useful for simulating LED loads by adjusting the resistance internally to maintain the voltage. Similarly, there are modes like Constant Current (CC), Constant Power (CP), and Constant Resistance (CR) where one parameter is fixed while the others vary. CP mode is ideal for battery load capacity simulation, while CR mode is handy when you need the load to act as a resistor with varying voltage and current. The CC mode is suitable for basic current sinking applications to test if the input supply voltage drops at constant currents.
So, what are things you need to look at before you purchase an electronic load? For hobby and non-precision applications, you can build one or get relatively cheap ones online. The one shown in the picture is a 150W load capable of operating in all the modes mentioned earlier. If you need something more advanced, there are benchtop models that are slightly more expensive. Start by determining the capacity rating required for your application, then you can narrow down your options based on size, the number of independent channels, and price. Remember these considerations and modes before you decide to buy one.
