Battery Emulators VS. Power Supplies & Electronic Loads
Battery emulators are bi-directional, whereas power supplies and loads are unidirectional devices. A power supply regulates voltage and expects some amount of current to be drawn. Electronic loads regulate current and expect voltage to be provided. Being uni-directional, these devices are unable to accept or supply power in the reverse direction.
An approach engineers often take is to build their own test setup using sources and loads. This can be challenging, and time consuming, and has many of the disadvantages of the common DC bus architecture described above. Typically, DC sources have a programmed response time of 10 to 100 ms, which is far too slow for today’s EV applications such as electric powertrains. For example, using a DC load to modulate power or provide a return path for back-EMF requires complicated software development, considerable integration and test time, and does not provide an accurate simulation of the battery’s internal resistance. Additionally, the load must consume power at all times, and since it is not regenerative, all of the power is dissipated as heat waste, increasing operating costs and creating uncomfortable work conditions.
Battery emulators maintain a positive DC voltage and can immediately accept or deliver current, allowing power to flow in either direction. More advanced battery emulators, like NHR’s 9300 Battery Emulator, allow further real- world simulation of battery characteristics by modeling the battery packs series-resistance (RINT).
The RINT Model: Accurately Simulating Battery Characteristics
The Internal Resistance (RINT) model provides a simulation of the battery’s internal chemical resistance, along with additional pack resistances created by internal connections, contactors, and safety components. The RINT model can be implemented with a true bi-directional source (Vocv) and a programmable series-resistance (Rs). This model is sufficient for understanding the major characteristics of battery-based resistances and pack resistances. While the number of mathematical models has increased, these more complicated models are used to understand the electro-chemical characteristics of batteries, the nuances of which have little impact on the overall system when compared with the total resistance of the pack.
NHR’s battery emulators feature this equivalent RINT Model providing an electronically programmable “Battery Emulation” mode. As in a real battery, NHR’s battery emulators adjust the output voltage depending on the direction and amplitude of current flow. This automatic adjustment of output voltage better simulates real-world battery pack characteristics especially when compared with common DC-bus and source/load simulation systems.
Need Help? Contact Us
Battery emulation is ideal for applications such as electric powertrain, fuel cell emulation, energy storage systems emulation, Solar PV inverter testing, DC Bus emulation, and more. For more information about key differentiators and technology considerations for battery emulation, please contact us.