How can I record longer lectures from myself?

I would like to record my own longer lecture (3 hours) in a lecture room as a video. How do you do it today?

Mobile phones do not record for a long time. Laptop and webcam?

What recording technology is there that shouldn't be that expensive?

Photo camera with "recording function" and a corresponding external memory card.

I once used my NIKON CoolPix with tripod and recorded it for 2 hours