Regular FPS drops in battery mode

I am attempting to run Path of Exile on my new notebook computer. Specs:

Intel i7 3610QM (4 x 2.1GHz)
Nvidia Geforce GT650M 2GB
8GB RAM

Now, it runs fine when plugged in. However, when on battery mode, I encounter these consistent fps drops. For about 5 seconds I get perfectly fine performance, then the next 5 seconds it'll drop to ~15 FPS. This repeats over and over.

I made sure my notebook is running in high performance mode, and I set every option in power management to the same value as when plugged in.

Screenshot

Also, this doesn't happen in other games.