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 the wiring before you pull the wire.
Build a diagram with your batteries, chargers and other equipment. Get wire and fuse sizing, check voltage drop, and spot problems before you start installing.
Free for up to 10 equipment components. No account needed.
Cables, busbars and fuse hardware don’t count toward the limit.
For boats, campervans, RVs and off-grid cabins
A live example. A 100 Ah lithium battery, 175 W of solar through an MPPT, a fridge and cabin lights.
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. This run is fine as drawn.
Hover any cable for its wire size and fuse.
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.
How 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 300+ 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
- A fuse that can't break the bank's fault current
- Too much voltage lost between the battery and a load
Wire, fuse and voltage-drop results update as you draw, and 50+ checks flag potential problems on the drawing while you can still change the plan.
300+real parts to pick from
50+checks running while you draw
ABYC E-11the marine standard the wire and fuse sizing follows
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. Drawing, sizing and checks run in your browser, free up to 10 equipment components; cables, fuse hardware and busbars never count toward that limit. Without an account your work stays on this device. Sign in for free to save and sync one project across your devices. 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.
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 does Crimp Pro unlock?
Crimp Pro is a one-time purchase that adds unlimited equipment, unlimited cloud projects, project and image exports, printable installation blueprints, share links and 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.
Where do the numbers come from?
Wire sizes come off the ABYC E-11 ampacity tables and fuses off the standard rating ladder. Voltage drop is measured against the allowance E-11.14.2.6 sets for that circuit — 3 % on panel feeders, bilge pumps, electronics and navigation lights, 10 % on general lighting — and you can override it per cable. ISO 13297 covers the same ground for boats built to EU rules. Cranking circuits get a class-T sized to ride the crank, and are exempt from the continuous-load derating and the fuse-≤-ampacity cap the way E-11 exempts them.
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.