Fuel cell testing solutions

　　What is a fuel cell?

　　The basic working principle of all fuel cells is the same: converting the chemical energy of hydrogen into electrical energy. However, several different types of fuel cell technologies have been developed. In addition to PEM , PAFC and SOFC , there are also alkaline fuel cells ( AFC ) and molten carbonate (MC) fuel cells. Among them, PEM fuel cells are widely used in the automotive industry due to their relatively low operating temperature and high efficiency.

　　However, a single cell can only generate a voltage of no more than 1V. Therefore, when testing low-voltage energy sources such as fuel cells, the test equipment has the problem of how to carry a large current under low voltage conditions. Currently, the electronic load used to test fuel cells will try to reduce the internal resistance to the minimum, but the internal resistance cannot be zero. Therefore, we need to use other methods to try to obtain the most accurate test results.

　　Introduction to ITECH testing solutions

　　Hardware Requirements

　　Nowadays, electronic loads all have internal resistance, so when the current is large, the corresponding minimum load voltage is higher. So how can we achieve low voltage load or even OV load?

　　At this time, we need an "auxiliary power supply" whose function is to provide a voltage that enables the internal transistor of the load to operate in the linear region when the electronic load carries different currents, that is, the minimum operating voltage.

　　Take the ITECH IT8811 electronic load as an example, as shown in Figure 1.

　　It is obvious from FIG. 1 that the greater the load current, the higher the minimum operating voltage of the load.

　　To achieve 0V load on the electronic load, the "auxiliary power supply" can be a very common voltage regulator, but the current parameter must be higher than the maximum current value that the electronic load needs to carry.

　　Solution Architecture

　　Knowing the specific requirements of the "auxiliary power supply", let's take a look at the wiring method and various points to note for implementing this test solution. As shown in Figure 2, we connect the "auxiliary power supply" and the fuel cell in series, and then connect the sense end of the electronic load to the positive and negative electrodes of the fuel cell.

　　It is not difficult to see the wiring method of this test solution from Figure 2, but the necessary point to note is that the remote sense function of the electronic load must be turned on and the positive and negative sense wires must be connected to the positive and negative electrodes of the fuel cell. The purpose of this connection method is to make the voltage sampled by the sense end of the electronic load the voltage across the fuel cell, so that the voltage displayed on the electronic load panel is the actual voltage across the fuel cell, so the auxiliary voltage of the "auxiliary power supply" can be ignored.

　　Precautions

　　1. Since the current noise of the "auxiliary power supply" itself will be superimposed on the test product, we need to choose a low-noise "auxiliary power supply" as much as possible.

　　2. The rated power of the electronic load must be greater than the sum of the power of the test product and the power of the "auxiliary power supply". For example: if the power of the test product is 100W, it is not enough to select an electronic load with a rated power of 100W. Assuming that the power of the "auxiliary power supply" is 50W, the rated power of the electronic load needs to be above 150W.

　　In summary, the difficulty in testing fuel cells and low-voltage products lies in the load test at 0V or ultra-low voltage. The test solution provided by ITECH is simple, convenient and low-cost, and can achieve 0V load without special hardware support. ITECH can provide both the electronic load and the "auxiliary power supply" mentioned in the test solution.