you will probably find that gaming performance on battery is a lot less than on mains. That statement however is from my own experience with gaming laptops and the batteries inability to give enough power to the GPU so it runs in a lower power mode so that it doesn't crash the system.
You should be benchmarking with the games you want to be playing really. If you want some synthetics however i would be looking at the latest benches from 3dmark probably timespy or port royal.
for cpu i would get Cinebench R20.