12 V Integration for Vanlife Smart Locks: DC-DC, Fusing & Parasitic Draw

Power the lock like a gentleman: safely, quietly, and without killing your starter battery.

1) Source Selection

• House battery only. Never the starter battery. If you must, add a low-voltage disconnect (LVD).
• Use a proper DC-DC charger between alternator and house bank; don't tap OEM harnesses.

2) Protection & Conversion

• Fuse within 20 cm of the source (0.5–1 A slow-blow typically sufficient).
• Buck converter near the door for 12→5 V systems; set 5.1 V, verify under actuation.
• TVS diodes: 18 V on the 12 V side; 5 V on the lock input.

3) Parasitic Draw Planning

• Typical idle 0.2–0.5 W → 4.8–12 Wh/day. Budget in your energy model.
• Add a master kill switch for storage; lock remains mechanical with key.

4) Wiring Discipline

• Twist positive/negative pairs to reduce induced spikes; separate from fridge & inverter cabling.
• Ferrules on screw terminals; strain relief at every transition.

5) Test & Log

• Measure current at rest and during actuation; write it on your service card inside the door.
• Road-test over speed bumps; re-torque after 100 km.

Related Reading

• Vanlife Smart Lock Retrofit Strategy — Mounting and wiring routing.
• House vs Starter Battery: Isolation, LVD & Storage Mode — Battery selection.
• Cold-Start Behavior in Vans — Battery performance.