MongoDB Lookup Issue
Yes, you can use the $lookup operator as part of an aggregation, after you $unwind the batches array. For example:

db.collectionA.aggregate[

  { $unwind: "$batches" },

  { $lookup:
    from: "collectionB",
    localField: "batches",
    foreignField: "_id",
    as: "collectionB"
  }
]