You should specify what you mean. The second battle he ever won?
The second battle of the Gallic Wars? The Second battle of Caesar's
Civil War? Which one?
It the first case, Caesar first command an army when he was
appointed governor of Hispania Ulterior (Further Spain) in 62 BC.
There he fought in Lusitania. I do not have information about the
battles he fought there.
In the second case, the second battle of the Gallic Wars was the
battle of Bibracte against the Helvetii in the department of
Saône-et-Loire in France in 58 BC
In the third case the second battle of Caesar's Civil War was
the Battle of Dyrrachium in Albania in 48 BC.