Yes, I have tried Low Tier Batteries.
If IC2 Classic is installed and CoFHLib is not installed, Computer Cases can be powered by Ultra Low Voltage Batteries, although two pieces of tin wire are needed to power Computer Case Tier 1. To power from more powerful batteries, you need OC Power Converter, which has the highest limit.
If CoFHLib is installed, then there are no significant losses when powering Computer Cases from Ultra Low Voltage Batteries. OC Power Converter can be powered by more powerful batteries without loss.