Grammar fix
charge up
fill the battery
To charge up a device is to plug it in and fill its battery with power.
phrasal verbB1core
Hear it in context
Notice where the phrase sounds natural.
I'll just charge up my phone before we head out — it's nearly dead.
Have you charged up the speaker? We'll need it for tonight.
Fix the pattern
One small grammar move makes it sound right.
Not: I need to load up my phone.
Say: I need to charge up my phone.
Batteries 'charge up', not 'load up' — 'load' is a false friend here.