Here's why:
* Spelling: The "a" in "batter" is followed by a double consonant ("tt"). This is a common indicator of a long vowel sound in English.
* Pronunciation: The "a" in "batter" sounds like the "a" in "father", which is a long vowel sound.
So, while "batter" might seem like it should have a short vowel sound because of the double consonant, it actually has a long vowel sound.