Возьми зарядку с собой: она пригодится в дороге.

Зарядка is feminine nominative singular. After возьми (take), the direct object goes in the accusative.
For most feminine nouns ending in -а / -я, the accusative singular changes to -у / -ю:

• зарядка (Nom.) → зарядку (Acc.)
  So the phrase literally is Take (a) charger.

Both can translate as take, but the aspect changes the nuance:

• Возьми (imperative of perfective взять) = take it (once), make sure you take it → a single, completed action.
• Бери (imperative of imperfective брать) = take (in general / habitually / start taking), or can sound like go ahead, take it depending on context.
  In advice like this, Возьми is very common because it means don’t forget—take it with you.

С собой is the standard Russian way to say with you / with oneself when the subject is already clear (here, an implied you from the imperative возьми).

• Возьми … с собой = Take … with you
  С тобой is possible, but it usually emphasizes you as a person (with you, together with you) and can sound less neutral in this “bring it along” meaning.

The preposition с meaning with takes the instrumental case:

• с
  • Instrumental → с собой
    Here собой is the instrumental form of себя (oneself). So it’s literally with oneself, idiomatically with you.

It’s future, because пригодиться is perfective. Perfective verbs don’t have a true present tense meaning; their “present-form” conjugation refers to the future:

• пригодится = will come in handy (not “is coming in handy”)

Зарядка is grammatically feminine, so the pronoun referring to it is она (she/it).
Even though in English you’d say it, Russian matches the noun’s grammatical gender:

• зарядка (f.) → она

В дороге means on the road / while traveling / during the trip.
After в meaning in/during, Russian uses the prepositional case:

• дорога → дороге (Prepositional)
  So в дороге is literally in (the state of) traveling.

Yes, with slightly different typical usage:

• в дороге = while traveling, often emphasizing the trip as a process.
• в пути = also en route / while on the way, a bit more “travel/status” sounding.
• по дороге = often on the way (somewhere) and can imply during the route, possibly stopping or doing something: По дороге зайдём в магазин (We’ll stop by the store on the way).
  In your sentence, в дороге or в пути are the closest matches.