The HDS units with LSS-1 StructureScan boxes definitely need to have a dedicated circuit run directly from the battery. Preferably with an in-line master disconnect switch added between the battery and the units. Unless the StructureScan boxes are switched seperately with a toggle switch or with an in-line master disconnect switch they will continue to draw latent voltage even with the HDS units powered off. The HDS units surge 2.2 amps on start-up and operate at 1.3 amps which is just slightly less than an aerator pump. Also if the HDS unit/units are equipped with a NMEA backbone it should also connect to the master disconnect circuit as it to will continue to draw voltage even with the HDS units powered off eventually running the battery down unless it is charged continuously or used frequently. The HDS units don't like low voltage and anything under 10 volts will cause them to do crazy things. If they are wired to the starting battery and voltage drops below 10.8, starting the engine may turn the units off. It may work but the 16 - 18 ga wiring installed on most boats is not a reliable power source for the HDS/StructureScan units.