I hope you are refering the answer to the question that had the figure shown above.
I mean that 8V battery as second battery. The other battery is having higher emf 20V.
If you look the figure, 8V battery is getting charged from 20 V battery. When two batteris are connected in a loop along with some resistors as shown in this figure current will flow from battery of higher emf to battery of lower emf and battery of lower emf is getting charged.
Hence all the current flowing in the circuit is delivered by battery of EMF 20V