Home › Builds › 24 V truck or boat cabin: 12 V for a fan and a lamp, USB for a phone, and a 24 V fan, from a 24 V battery

24 V truck or boat cabin: 12 V for a fan and a lamp, USB for a phone, and a 24 V fan, from a 24 V battery

Bench build · Everyday gadgets · Intermediate · about 30 minutes

12 V and USB power in a 24 V vehicle, plus a 24 V cabin fan. Trucks, buses and many boats run on 24 V, and most gadgets want 12 V or 5 V. From the 24 V battery, through a 10 A fuse: a buck module set to 12 V runs a 12 V fan and a 12 V lamp; a USB step-down module (9–36 V in) charges a phone straight from 24 V; and a 24 V fan runs directly. Never plug a 12 V gadget straight into 24 V: it burns.

24 V truck or boat cabin: 12 V for a fan and a lamp, USB for a phone, and a 24 V fan, from a 24 V battery: the finished build running on the simulator's bench

Build it in the labGuided build, test sheet and fault finding, free in your browser.

zencircuitlab.com/l/24v-truck-boat-cabin

Parts list

Test procedure

Each test has an expected value and a pass range, like a factory test sheet:

  1. 12 V rail
  2. USB port
  3. 24 V fan speed
  4. Battery current

How it works

What it does: 12 V and USB power in a 24 V vehicle, plus a 24 V cabin fan.

Build it (guided or ready-made), then run its test procedure below. Every test has an expected value and a pass range, just like a factory test sheet.

Background

The cigarette-lighter “24 V to 12 V converters” in truck stops are a buck module in a box.

More builds: everyday gadgets