Hi Sirani,
I think the Battery Bus will still remain powered if you lose transfer bus 2 and the battery is discharging. The key busses you will lose are the Hot Battery Bus and the Sw. Hot Battery Bus. In this situation your decision was good if you were in a single battery equipped aircraft. In a dual battery aircraft both buses should remain powered via the aux. battery charger. The system will last much longer than the 30 mins. as quoted in the loss of all generators scenario and being on battery power. I have a 737 guide which gives a number of 2 hours but it actually could be quite longer than this if you could minimize the load on the battery. I would treat this scenario as a land soon but not land ASAP. Soon will have a different meaning for each captain. This is why we are paid to make decisions as Captains. Not all things are black and white and this scenario gives you little to no guidance from the QRH. The Transfer Bus off checklist is also leaving you hanging out to dry with little guidance.