Lenovo Y500 doesn't run games fast if not charging?

This happens because the battery doesn't have enough energy to power the screen, processor and gpu all at once under full load. The system throttles power consumption by the GPU. I've looked in the nvidia control panel, and there's not really a setting to change, except the option Power management mode to prefer max performance.

It's normal though, so it's not a defect in your machine. My y400 does the same.

Also, I recommend changing your power plan so that it stop charging the batter at 60% or so and just runs as though it where a desktop plugged directly into the wall. You'll notice that the battery will last loads longer that way (health wise. You should still periodically charge it all the way up, then drain it all the way down)

Hi

Modern games are resource-hungry in terms of memory, graphics and CPU resources.

Using the battery modifies the performance parameters according to a range of preset battery efficiency modes. So batteries in conjunction with resource-hungry games can be problematic.

Using a laptop for extended periods with a battery installed while simultaneously plugged into the mains will eventually damage either the battery or the motherboard's power management system.

If you play the game for extended periods, the best advice is to remove the battery once it is fully charged and then use the laptop plugged into the mains without the battery. Then restore the battery and unplug from the mains when you have finished the game.

For full efficiency and long life extended indoor periods of use should be batteryless, the battery should be fully charged and discharged regularly, always unplugged from the mains when fully charged, charged without delay on receipt of critical low power warning messages and should never be left fully depleted for long periods of time.

I hope this helps

Rgds

Stoic

Try changing the power options from whatever you have it to "High Performance." Usually when you unplug a laptop, windows will change the power settings to conserve battery.