You can perform battery simulation directly on the 2281S and generate charge models using the unit. The manual provides complete instructions and capabilities:
https://www.tek.com/en/tektronix-and-keithley-dc-power-supplies/2281s-manual/series-2281-precision-dc-supply-and-battery
We do provide software options for generating and running simulations.
Our KickStart software has a Battery Simulator Specialty Application that will allow you to create a model using the 2380 Series electronic loads and then run your simulation on the 2281S. You can find More information on the KickStart landing page:
https://www.tek.com/en/products/keithley/keithley-control-software-bench-instruments/kickstart
You can also find a video showing the software in use here:
https://www.tek.com/en/video/product-demo/how-to-use-keithley-kickstart-battery-simulator-app
If you have used our graphical TTI Source Measure Units in the past to generate your models, such as the Model 2450, you can use the script attached.