I think I understand the miscommunication here, the 1507 motors can be supplied with a minimum 3S voltage, which means 3 nominal LiPo cells (3.7 Volts) arranged in series to give 11.1 Volts
The current required by your motors determines how many nominal LiPo cells are needed in parallel to supply the required current.
I did my calculations assuming the largest compatible battery back which was a 4S Lipo battery, but the peak current requirement is likely still similar.
It took me weeks to get my head around LiPo batteries when I first started building robots.
This video is targeted at children but still the most useful explanation I have found.
