From google dictionary: /əˈkəlt/
From my textbook: ['ɔkʌlt, ɔ'kʌlt, ə-]
The difference of those two is HUGE, Could you give me an explanation ?
In practice, the distinction between /ʌ/ and /ə/ is close to nonexistent in English. They are very similar phonetically, and [ə] can only occur in unstressed syllables, while [ʌ] can only occur in stressed, closed syllables. Because of this many linguists consider them to be allophones, and many dictionaries transcribe them with the same syllable or treat them interchangably. So the fact that your textbook has [ʌ] while google has [ə] is of little significance.
The only other difference between the two transcriptions is the treatment of the first syllable. I believe that the pronunciation with stress on the first syllable is non-standard, but if the first syllable is stressed, then the vowel is unambiguously [ɔ]. If the first syllable is unstressed, then [ɔ] will normally be reduced to [ə], which your textbook has as an alternate.
So they're not very different, after all.
[Edit: If I'm picking nits, I would point out that the second syllable in my speech has no vowel at all, but rather a syllabic /l/: [ə'kʰl̩t]. The vertical line beneath the [l] indicates syllabicity. However, I've never seen a dictionary that actually transcribes syllabic liquids as such, since it tends to freak out language learners, and linguistically naive native speakers disbelieve in them.]