Refitting a sailboat
House bank, starter battery, a panel on the rail and the long run to the bow. Crimp keeps the fuses at the bank and the gauge honest over the distance.
Free · works in your browser · no account needed
Plan the wiring before you pull the wire.
Drag in the battery, charger and gear you actually own, draw the cables between them, and Crimp tells you which wire and fuse each run needs — and what would go wrong — before you buy anything.
For sailboats, campervans and off-grid cabins · 12 V and 24 V
A live example. A 100 Ah lithium battery, 175 W of solar through an MPPT, a fridge and cabin lights.
Hover any cable for its wire size and fuse.
What Crimp worked out
The cabin-light run, 3.5 m
- Wire
- 1.5 mm² · AWG 16
- Fuse
- 3 A
- Voltage drop
- 1.3%
Well inside the 10 % voltage-drop allowance for cabin lighting. This run is fine as drawn.
Open this example in the editorWho it's for
Made for the systems people actually build.
You don't need to know the standards. Bring the parts you have and the place they're going in — Crimp brings the rules.
Building out a campervan
Lithium bank, a DC-DC charger off the alternator, solar on the roof, a fridge and lights. Crimp checks the charger against the alternator and sizes every run.
Adding solar to a cabin
A 12 V or 24 V bank, an inverter and long runs to the far room. Crimp checks the voltage drop so the light at the end still comes on bright.
How it works
Three steps. No spreadsheet.
Pick what you own, draw the cables, and read the answer on the drawing — not in a calculator somewhere else.
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
See what would go wrong
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 point at the problem on the drawing — before anything is bought or crimped.
300+real parts to pick from
50+checks running while you draw
ABYC E-11the marine standard the wire and fuse sizing follows
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!”
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, 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?
One developer in Sweden — Twinbolt AB. 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 nothing to sign up for. Your drawing saves on this device, and you can add the rest of the boat later.