Look at the documentation http://api.rubyonrails.org/classes/ActionView/Helpers/FormBuilder.html#method-i-collection_select
collection_select(method, collection, value_method, text_method, options = {}, html_options = {})
# method: the field in your form's object
# collection: the collection of active records to display as options
# value_method: which method call in items of the collection to get the displayed value
# text_method: which method call in items of the collection to get the id value
So in your case:
<%= f.collection_select :bat_id, Manufacturer.all, :id, :name, include_blank: true %>
Given that Manufacturer
model has a name
field, otherwise you need to adapt