Sounds like good advice . Long runs with small wire or bad connections can cause voltage drop. THe unit reading low voltage not on black box . I would consider a Lithium battery to run both . It is small and can be installed up close to units on most boats as very small . I run 1242 and black box on one 32 AH from Amped outdoors . It has been running them about 16 hours . Rated 14.8 volts and charges to 16.8 volts . Never drops below 12 volts before shutting off . Here is my battery box I rigged up with quick connects . Just a plastic ammo box from Harbor Freight and quick connects off Amazon . Protects battery and quick connects great to hook unit , then charger and then just to shut off power by leaving unplugged . I soldered both unit wires each to one quick connect .

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