It depends on what you need. But you should start by looking at Keithley's SourceMeter "source measure units" and competing instruments from Keysight and Rohde & Schwartz. There are even specific instruments in this vein that can emulate battery charge/discharge models out of the box. These are typically called "battery simulators" or "battery emulators".

https://www.tek.com/en/products/keithley/dc-power-supplies/2... https://www.keysight.com/us/en/product/E36731A/battery-emula...