Why does the second sentence use 个? I read this sentence today :


  每天给自己的手机充电，
  也不要忘了给自己的口语充个电！


I wonder why the second sentence use 个 between 充 and 电 while the first one doesn’t.

Could anyone please explain it to me?
It’s vernacular language.


  Charge your phone every day, and don’t forget to also give your speaking [skills] a charge!


個 is a generic counter for an event or session in this case, and will commonly be heard in a casual spoken style.

You can get similar constructions e.g.


吃個飯 (have a meal)
旅個遊 (go on a travel)