My laptops battery isn’t amazing and dies after two lectures at Uni so when I have a 7 hour day and there isn’t much in the way of plug sockets around, I’m stuffed
Honestly you should just get a Chromebook. It will last all day and is cheap.
Do what @CraigW said.
I have Chromebook and lasts if i’m not super bright on display about 9 hours.
I have a Pixel C which is about twice the cost of a Chromebook, lasts about a similar time but being USB-C I can use Anker products to top-up (and at back of my mind a Powercore 26800 would be a good pairing).