Additional battery at Ford Transit Euroline??

Hello together!! I have been the proud owner of a Euroline Bj 2011 for a few weeks! Now my question: Where is the additional battery? Lt. Westfalia additional description should you be under the passenger seat, but there is yawning void 😉 There are probably 2 batteries installed under the driver’s seat! Which is the additional battery?? Which consumers run over the starter battery (radio, light)? And where could I possibly connect a Cetek 5.0 MXS charger if I have somewhere for a few T age would like to stand incl. overnight stay and cooler??? The description does not help any further ;-( Maybe (determined) you can help me Thank you Grüß Gipfelzigeuner