Solution : https://service.sap.com/sap/support/notes/390242 (SAP Service marketplace login required)
Key words : 
enter data type meprwe, select 'data type', enhance structure meprwe, purchasing info record, me21 solution implement, start transaction se11, 'compent type' column, component type charg_d, terms quantity conversion, purchase order item
Related Notes : 
       
| 1339273 | Qty conversion in condition rec. for active ingredient mgmt | 
| 1226419 | Batch information in PO item not passed for pricing | 
| 817589 | ME59: Wrong net price when Requisition item has a batch | 
| 668906 | ME22N: change batch : weights and volume not re-determined | 
| 571786 | Batch not transferred to price determination | 
| 568209 | Pricing not considering batch specific conversion factors. | 
| 556013 | ME21: Transfer quantity conversn SD document->purchase order | 
| 549013 | Wrong valuation at GR when using batches | 
| 529748 | Copying a purchase order item with batch | 
| 490331 | Wrong valuation at GR when batch specific units of measure |