Where is the aux battery located on a 1994 Coach House 192TB

An old-time friend had a Coachman motorhome and did not want to run a lot of wiring from his understep battery. So he had a carpenter make a tiny box just to fit a meter pair and put a 45 degree angle on the face so he could look down and read the meter. His idea worked like a champ. Three and a half feet feet of wire.