ADV4X4 Power System Builder

Plan a 12 V, 24 V, or 48 V system. We pick the wire size and fuses, draw the wiring diagram, and make a shopping list. No electrical experience needed.

How this works: 4 easy steps
  1. Pick your battery. Tell us what you will power your gear from.
  2. Choose a fuse box or switch panel if you want one. This is optional.
  3. Add what you want to power, like a fridge, lights, or a fan. We already know typical power use for common gear.
  4. Set up charging if you want it, then check your plan, save it, or print it.

Not sure where to start? Use a template and change anything you like.

Step 1: Your battery

Everything else is sized around this. If you are not sure, leave the suggested choices.

More battery options

Step 2: Fuse box or switch panel (optional)

A panel gives you one tidy place to fuse and switch your devices. Skip it if you want each device wired on its own.

Step 3: What do you want to power?

Tap a popular item to add it, or choose from the full list. We fill in typical power use for you. You can change anything.

Your loads

Step 4: Charging and outlets (optional)

How will your battery get recharged, and do you want household outlets in your rig? Each option has its own page that explains it in plain English.

Advanced wiring settings  (most people can leave these alone)

These are the defaults used to size every wire and protection device.

Your wiring diagram

How to read this diagram
  • Red lines are positive wires. Black lines are the negative return and ground.
  • Thicker lines mean thicker wire. Each wire is labeled with its size in AWG, and a smaller AWG number means thicker wire.
  • Yellow boxes are fuses or breakers. Each one protects the wire next to it.
  • The big red bar is the positive bus bar and the big black bar is the negative bus bar. They join everything together.
  • The key under the diagram explains every symbol.

Wire and fuse list (every circuit)

Wire ends and crimpsSee which terminals and tools each wire needs, and how to crimp them so the connections last.

Shopping list

Wire ends and crimpsSee which terminals and tools each wire needs, and how to crimp them so the connections last.

How this is calculated (for the curious)

  • Load current = watts ÷ battery voltage. Fuse = 125% of that, rounded up to a standard size.
  • Wire = the smallest copper gauge that stays under your voltage drop limit and is rated for at least the fuse size after the routing derate.
  • Voltage drop counts the round trip (2 × run length) with 10% extra resistance for warm wire.
  • The battery cable and main fuse carry whichever is larger: all loads on, or all charging sources at full output.
  • With a distribution panel, the feed wire and protection carry the panel's loads. The feed's voltage drop (2% limit) is subtracted from each panel circuit's drop limit. Loads go on the smallest circuit that fits them. Anything that does not fit is wired direct to the bus bar.
  • Ampacity values follow ABYC-style tables for 105°C copper. Smallest wire used is 16 AWG (12 AWG for chargers).

Grounding, shunt, and protection notes

    Glossary: what do these words mean?
    AWG
    American Wire Gauge, the standard size for wire. A smaller number means thicker wire that carries more power. 10 AWG is thicker than 16 AWG.
    Amp (A)
    How much electricity is flowing. More amps need thicker wire and a bigger fuse.
    Volt (V)
    The pressure of electricity. Truck and camper systems run on about 12 volts.
    Watt (W)
    How much power something uses. Watts equal volts times amps.
    Amp-hour (Ah)
    How much energy a battery holds. A 100 Ah battery can supply 1 amp for 100 hours, or 10 amps for 10 hours.
    Fuse
    A safety part that melts if too much current flows, which stops a fire. You replace it after it blows.
    Circuit breaker
    A switch that trips if too much current flows. You reset it instead of replacing it.
    Bus bar
    A metal strip where several wires connect together, like a power strip.
    Ground or negative
    The return path for electricity back to the battery. Every positive wire needs a matching negative.
    Shunt
    A small device that measures how much power goes in and out of the battery.
    BMS
    Battery management system. It is the protection circuit inside a lithium battery.
    Alternator
    The part of your engine that makes electricity while you drive.
    DC-DC charger
    A box that safely charges a second battery from your alternator while you drive.
    Solar charge controller (MPPT)
    A box between your solar panels and the battery that charges it correctly.
    Inverter
    A box that turns 12 V battery power into 120 V household power for plug-in devices.
    Voltage drop
    Voltage lost along a wire. Long or thin wires lose more. We size the wire to keep this small.
    AGM, EFB, flooded
    Types of lead-acid battery. AGM is sealed and common in trucks and campers.
    Lithium (LiFePO4)
    A lighter, longer-lasting battery type that can safely use most of its capacity.
    CCA
    Cold-cranking amps. How strongly a battery can start an engine in the cold.
    System voltage
    The voltage of your whole battery setup. 12 V is standard for trucks and campers. 24 V and 48 V use fewer amps for the same power, so the wire can be thinner.
    Series
    Batteries joined end to end, positive to negative. Their voltages add up and the amp-hours stay the same. Two 12 V batteries in series make 24 V.
    Parallel
    Batteries joined positive to positive and negative to negative. Their amp-hours add up and the voltage stays the same. Two 100 Ah batteries in parallel make 200 Ah.

    Device draws are typical values, not guarantees. Check the label on your own gear and follow the manufacturer's manual where it differs. This tool is a planning aid, not an engineering sign-off. Verify against the ABYC, NEC, or RVIA guidance that applies to your build, and use pure copper wire (not copper-clad aluminum).