All Hyundai Robots need 2 or 3 batteries to maintain the encoders when the power is removed. There is also a battery for the controller memory.
We recommend that your replace the batteries every two years.
I spent 1 day yesterday bringing a robot back to life after a company let the batteries go down, so this can be costly. Get your batteries.
Alternatively we can provide a service agreement for carrying out inspections of the installation and maintenance for your robots.