Customer returns and repair them send back to customer

Hi All,

I have a scenario like,we have taking back the customer return through return oder> return delivery>PGR.

Actually here My user does not know the batch number of this product,he will create PO with material ID,That will create Return order for me.I will create the new batch for this item while doing PGR.

After getting back the material into my storage location,we will create one repair order  for ME(SD and ME Integration).After material got repaired,how to trace that material along with batch number to send back to the same customer?.Is there anyway that I can refer prev doc to create free of charge order for my customer.I have heard that after repaired,the item got a new batch number altogahter.Is this correct?can't we got the same batch number which we sent to ME through repair ordr?

Thanks in advance

Kumar.