I also suspect that the limit does not quite match the description in OpenComputers.cfg. These limits are measured in OC energy. The Tier 1 Computer Case has a limit of 5/tick. Given the conversion rate, it should take 12.5 EU/t, if I understand correctly. In practice, If IC2 Classic is installed and CoFHLib is not installed, its limit is below 8EU/t if it is powered by GT6.
Also, the power transfer rate is different in the scenarios “from GT6 Batteries when CoFHLib is installed” and “from IC2C Batteries”. The Tier 1 Computer Case has a capacity of 500 and a limit of 5/t. In the first scenario, it charges in 5 seconds, which is in line with theoretical calculations. In the second scenario, it charges in 12 seconds.