Batteries and banks
Lead acid or LiFePO4, single or in series for a 24V or 48V bank.
12 volt systems
Build a 12V wiring diagram that adds up
A 12V system is unforgiving: low voltage means high current, and high current means thick cable, short runs and fuses that match. WireElectric shows you exactly where that goes wrong.
Drawing and checking is free and works without an account.
- Free drawing, no account
- Victron components with real terminals
- Checks on cables, fuses and voltage
What can you draw?
Every part comes from the component library with real ports, voltages and currents.
Solar panels
Panels in series or parallel to a charge controller at the right voltage.
MPPT charge controller
Charge controllers between solar and battery, including Victron models.
DC-DC charger
Charging from the alternator or starter battery over a DC-DC charger.
Inverter
From 12V or 24V to 230V for your onboard appliances.
Shore power and charger
Mains connection with battery charger, RCD and circuit groups.
12V and 24V loads
Lighting, pump, fridge and other loads with a fuse per circuit.
230V circuits
Sockets and fixed connections behind your inverter or shore power.
Where 12V diagrams fail
Conductor too thin for the current
The check compares the load current with the ampacity of the chosen size and with the voltage drop over the length you entered.
Fuse does not match the cable
A 100 A fuse behind 6 mm² protects nothing. Per branch you see whether the rating sits between the load and the cable limit.
Missing return path
The negative side is checked as strictly as the positive: every load needs a return path to the source through a busbar, shunt or ground point.
Automatic checks while you draw
WireElectric calculates along as you connect parts and reports what does not add up.
Wire size
The required cross-section follows from current, length and allowed voltage drop.
Fuses
A fuse that does not match the cable or the device is flagged.
Voltage drop
Per cable you see the loss in volts and percent.
Connections
Ports that do not match in voltage or type raise a warning.
Parts of a 12V system
Everything a 12 volt system needs is in the library:
- 12V batteries (AGM, gel, LiFePO4) single, parallel or in series to 24V
- Positive and negative busbars and distribution blocks
- MIDI, MEGA, ANL and blade fuses with holders
- Battery switches, split charge relays and low voltage disconnects
- Shunt and battery monitor for the real state of charge
- Loads: fridge, water pump, LED lighting, fan, USB chargers
Building the diagram
- 1
Battery and main fuse
Start with the bank, the positive and negative busbar and a main fuse right at the positive terminal.
- 2
Monitoring and charging
Put a shunt in the negative lead and hang the charge sources on the busbars: solar through a controller, the alternator through a DC-DC charger.
- 3
Distribution and loads
Fuse block or distribution panel, switches and the 12V loads with their power rating.
- 4
Enter the lengths
Fill in cable length and size per connection; only then can voltage drop be calculated.
Example wiring diagrams for campervan, boat and off-grid
Calculate it yourself
Every calculator answers one question about your installation. WireElectric then runs the same calculations for every connection in your complete diagram.
Wire gauge calculator
Find the cross-section that suits your 12V or 24V system, based on current, length and voltage drop.
View →Fuse size calculator
Find a suitable fuse for your circuit, including a check on whether the cable can carry it.
View →Voltage drop calculator
Check how much voltage you lose over a cable and what reaches your load.
View →Battery capacity calculator
Work out how much battery capacity in Ah you need for your daily use and autonomy.
View →Battery runtime
Calculate how long a battery can power a load, including the usable share and inverter losses.
View →Watts ↔ Amps
Convert power straight to current at 12V, 24V, 48V or 230V.
View →Solar panel calculator
Work out indicatively how many Wp of solar panels your daily consumption needs.
View →Build a 12V wiring diagram that adds up
At 230V hardly anyone worries about voltage drop; at 12V it is the first problem. A 1000 watt load draws over 80 amps at 12 volts, and over five metres of thin cable you lose so much voltage that the inverter shuts down. On top of that a fuse protects the cable, not the appliance, so its rating has to match the conductor size. The app does that arithmetic per connection while you draw.
You can start drawing without an account.
Open WireElectricQuestions about 12V wiring diagrams
- How much voltage drop is acceptable at 12V?
- For lighting and sensitive electronics 3 % is common, for inverter cables 1 to 2 %. Our voltage drop calculator shows the effect of length and conductor size immediately.
- Which fuse goes with which cable?
- The rating sits above the continuous current (often 1.25 times) and below what the cable can carry. On the fuse calculator page you enter current and size and get the matching rating.
- Can I draw a 24V or 48V system?
- Yes. You choose the system voltage per net; all checks on conductor size, fuses and voltage drop use that voltage.
- Can I hand the diagram to an installer?
- You save it in your account and export a PDF, so an installer or inspector sees exactly what you plan to build.
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