Refitting a boat
Plan the house bank, starter battery and onboard loads together. Check cable sizes, battery protection and voltage drop along the longer runs.
12V and 24V wiring diagram software
Plan your 12V wiring.
For your boat, campervan or off-grid system.
- Size wires and fuses
- Estimate battery runtime and charging time
- Catch problems with 80+ wiring checks
Start free. No account needed.
Live example
What Crimp worked out
The cabin-light run, 3.5 m
- Wire
- 1.5 mm² · AWG 16
- Fuse
- 3 A
- Voltage drop
- 0.6%
Well inside the 10 % voltage-drop allowance for cabin lighting in this example.
Hover a cable for its wire size and fuse. Drag to pan or pinch to zoom.
Your tool identified I selected a larger amperage DC-DC charger and it would eventually smoke my small 75-amp alternator. I downsized to an 18-amp charger and all I can say is “Thank you — Thank you!”
Who it's for
Start with the system you're building.
Choose a wiring example or check a cable run, then use your own equipment and distances to make the plan yours.
Building a campervan or RV
Connect the leisure battery, roof solar, fridge and lights. Start with a DC wiring example and adapt it to your equipment and cable routes.
Adding a second battery
Plan the starter-to-auxiliary-battery path through a DC-DC charger. See where the battery fuses and common return belong in the example.
Adding solar to a cabin
Plan a 12 V or 24 V battery system with solar charging and DC loads. Check how cable length affects voltage drop before routing wire to the far room.
A larger live example
See the whole system together.
Follow solar and alternator charging into a campervan’s house battery, then through the fuse block to the lights and roof fan. Open the same drawing to make it yours.
Campervan · solar and alternator charging
Starter and house batteries · SmartSolar MPPT · Orion XS · fused DC loads
Live Crimp simulation. Try the charging sources and loads, or choose Wiring to follow the connections.
View full screenRed = positive · dark = return. Crossings are not junctions. Read the assumptions before adapting a circuit.
A 12 V DC planning example. Replace the placeholder equipment and cable lengths, check the battery’s combined charging limit, and resolve the protection findings before installation. Mains and inverter circuits are outside this drawing.
See the cable schedule and assumptionsHow it works
From your parts to a wiring plan.
Choose your equipment, connect the terminals, and see cable sizes and checks on the same drawing.
1
Pick your parts
Start with the real battery, charger and loads from a palette of 334 parts. If yours is missing, make it once and keep it for next time.
2
Draw the cables
BAT +
4 mm² · 40 A
BUS +BatteryPositive bus
Connect the terminals the way you'd install them. Tell Crimp the length and it picks the wire and fuse for that run.
3
Check before you install
Worth a look before you install
- A DC-DC charger pulling more than the alternator can supply
- Too much voltage lost between the battery and a load
Wire, fuse and voltage-drop results update as you draw, and 80+ checks flag potential problems on the drawing while you can still change the plan.
334real parts to pick from
80+checks running while you draw
ABYC E-11the marine standard the wire and fuse sizing follows
Crimp for AI agents · public beta
Ask your AI. Check the plan in Crimp.
Connect ChatGPT, Codex or Claude Code to look up components, calculate wire and DC-DC charger sizing, or build a small draft you can inspect and edit. Missing facts and assumptions stay visible.
Use Crimp with your AI
No Crimp account or API key required.
Good questions
Things people ask before they start.
Anything not answered here reaches a person at [email protected], usually the same day.
Do I need an account?
No. You can start drawing, sizing and checking in your browser without an account. Without an account your work stays on this device. Sign in for free to save and sync all your cloud projects, edit them across devices, share links and use comments. Anything you hand to the AI also leaves your device; signing in raises the daily allowance.
Is it only for boats?
It's for 12 V and 24 V DC systems — sailboats, motorboats, campervans, RVs, overland rigs, off-grid cabins. The catalog leans marine and van because that's where the questions come from.
Can I use Crimp on my phone or tablet?
Yes. Create and edit drawings in your phone, tablet or desktop browser. Start on this device without an account, or sign in for free to save and sync your projects across devices.
What if my exact part isn't in the catalog?
Customise any component — rename it, change its current ratings, add or move terminals — or build one from scratch. Custom parts are saved in your own library and reusable across projects. Parts reported through the in-app feedback button regularly end up in the catalog.
What is included in a paid export?
Paid exports include the full printable blueprint, cable schedule and bill of materials. Pricing shows the offer available to you before you buy. Cloud sync, cross-device editing, share links, comments, diagnostics and simulation are free either way. Anything the AI drafts has its own daily allowance and is not sold as part of the licence.See pricing and export options
Where do the numbers come from?
Sized against ABYC E-11. Boats built to UK or EU rules answer to ISO 13297 — check these figures against it before you build. Results depend on the component ratings, cable lengths and installation conditions you provide. Missing information can leave a recommendation unverified. Read the sizing methodology and its limits.
Who makes this?
Twinbolt AB, based in Sweden. Feedback sent through the app is read by a person, usually the same day.
Start small
Start with one battery and one light.
Nothing to install and no account needed. Your drawing saves in this browser, and you can add the rest of your system as you go.