12V Power Distribution

I replaced my factory battery with a Group 48/H6  X2Power AGM dual-purpose battery by Northstar (search for a similar battery cover to mine here). I ran 12V from the battery, through a 100-amp circuit breaker, and to the back of the car via Stinger 4-gauge amplifier installation kit to a 200-amp relay on the driver’s side of the subwoofer panel. The relay is triggered by a voltage controlled switch, the APO3. The relay passes power so long as its supply voltage is above 12.7V, basically any time the engine is running, or for about twenty minutes after shutdown. Once the battery voltage falls below a preset threshold (I can set it for 13.05, 12.7, 12.1, or 11.8 volts) for a preset time (0, 5, 10, or 20 minutes), the 200A relay loses its trigger until the car is restarted and has run for a few seconds. The APO3 assures good battery health and no surprises as a result of a dead battery (been there, done that). From the relay, 12V travels along two circuits: 1) through a Stinger fuse and on to my subwoofer system; and 2) to a Blue Sea Systems fuse block which feeds a secondary battery system and a trailer lighting module, some USB fans, and a heating pad for my auxiliary battery.

An auxiliary battery? Yes, things just got even more complicated. HAHA! I knew I wanted more battery power when I started traveling with a refrigerator/freezer and operating my ham radios more frequently. The blue components in this photo are a 100-Ah Lithium Iron Phosphate (LiFePo4) battery with 120-amp BMS and an Orion-Tr DC-DC charger. The battery can power my transceivers at high power for hours on end; plus, they can run the fridge for a few days, if needed. The Orion-Tr charges the secondary battery at up to 30A without overburdening my factory alternator. This system powers the refrigerator/freezer, a 400-watt voltage inverter, a cellular signal booster, my transceivers through an “N8XJK Super Booster” voltage regulator, and even the car’s OEM 12V outlets. The starter battery is almost completely unburdened when the car is parked. I have plenty of fuses and circuit breakers in the system to allow me to isolate faults or completely secure power from any voltage source.

The Super Booster maintains a constant output of 14.2 volts (my setting), regardless of battery voltage. The Super Booster’s outputs feed a Blue Sea Systems fuse block that supplies regulated 12V to my communications system. Each of my amateur transceivers can easily draw enough power to cause a voltage drop at the battery, which can result in the radio being shutdown due to insufficient voltage input. The Super Booster ensures that the transceivers always sense sufficient supply voltage and maintain full output power.

As you can imagine, having all of this equipment in such a tight space can trap a lot of heat! I’ve never had a component overheat, but I still decided to add ventilation when I opted to make my rear seat delete a permanent change. The “delete” article describes how I implemented the ventilation and its basic function. In short, I have six thermostatically-controlled 3-inch USB-powered fans that force air through the equipment space any time key points reach 88°F. It’s not a perfect system, due to some leaks at the doors, but has proven to be very effective at holding the equipment space below 110°F on even the hottest days.

All components’ ground leads are tied to a common point on the electronics panel, which is then combined into a single 4-gauge wire. The 4-gauge wire leaves the panel and is fastened at a seatbelt anchor point that’s under the rear seat, just inches from the electronics panel. Some system component manuals call for individual ground wires to be run all the way to the negative terminal of the car’s battery; and some argue against using a car’s body for grounding electronics components. The choices can be confusing! All I know is the negative terminal of my battery is immediately fastened to a stud that’s welded to the car’s body. See a photo below. Electrically, this seat belt anchor is the same point, with nothing but uninterrupted steel between here and the negative battery terminal’s grounding point.

This 12-volt wiring system is overkill for my application, but it should never be the weak link in my setup. Read more about the subwoofer system and the ham radio system. See a video about this distribution system here.

More Complex Than Required,

Scott