sezyal wrote: Even if it's drained too low for some reason, 2h+ driving should back it up I guess?
That not necessarily true.
Most modern cars charge their batteries regenerative. During normal continuous driving the battery is not charged.
Charging is done when you slow down with the gears engaged (braking on the engine). Try to limit your braking (with the cars braking system) to a minimum and try to use the cars ability to store energy more.