How should I expand my batterylife? What else can I do?

I use Linux Mint with Gnome and a few extensions (3 extensions) and I already installed autocpufreq and tlp, but the lowest cpu powerconsumption I could achive is 15 watts. What else can I do/should try to extend my pathetic 2 hours of battery life?

My specs: Dell Latitude E6430 i5-3380M 12GB DDR3 240GB sata ssd Intel HD4000

The battery is a 72wh replacement battery, which can hold about 55wh.

For comparison with throttlestop and battery saver mode I could achive about 6 hours on windows. Fair I choose security over battery life, but is there nothing I can do that I didn’t do already?

Thank you for your time😊