Air carrier Captain reported a ground gate return to reconfigure DG cargo. The DG cargo was reconfigured and flight departed.

Narrative

The boarding and the pre-departure process was uneventful. We received an ACARS message that stated we had no planned DG. We pushed back from the gate without receiving the Final Weight Manifest (which is not an uncommon occurrence). Upon taxi-out; the First Officer sent the Late Weights Message; and then while we were holding short of the runway; I asked him to call Operations for an update. Operations responded saying that we had incorrectly loaded baggage; and that there was DG loaded into the aft cargo compartment; and they suggested we return to the gate. At the same time; we received ACARS messages from our Dispatcher; and the Load Planner telling us to return to the gate.At this time we were concerned about the DG on-board; because we had previously received the message of no planned DG; and did not receive a Final DG message either. We coordinated a gate return; and upon return I spoke with the ramp agent who stated we had a wheelchair battery that was stored in the aft cargo compartment; and was not secured by the required amount of baggage adjacent to it (I was then; and still am unaware of such a requirement; but assumed it was valid). I searched my manuals and was unable to find any more information on this particular situation. The ramp agent stated he needed to move 15 bags from the forward to the aft compartment. He moved the bags; and then returned to show me a picture of the 'DG' in question. I was concerned because the picture he showed me was of a battery; with a 'UN' label on it. I called the Dispatcher and he conferenced in the Load Planner. The Load Planner explained that this battery was allowable; and not considered actual DG and we were OK to depart now that the baggage was moved.I am filing this report because this loading error caused us to nearly depart with a potentially dangerous/illegal situation; and it caused an hour delay to our passengers; all of which was completely avoidable.