Batir (Spanish meaning, “to beat”) and its very common derivative, batido (meaning “milkshake” — you beat the ingredients together after all!) both come from the Latin battuere meaning the same, “to beat.”
From that same Latin root we get the English battery — think of the phrase, assault and battery! (Over time, the meaning shifted from beating, to artillery — that which beats the enemy to the ground, literally! — and then from there, to the electric power that powers the artillery, and from there, our more common modern definition of the word.) And batter, like the mixture you make while cooking — that’s you beating the eggs together, right?
The b‑t root is visible in all these words.