Inverters

Job and waveform

An inverter makes AC from DC. Choose pure sine wave for a general camper system; modified sine can overheat, buzz or misbehave with motors, chargers and electronics.

Size from simultaneous loads

Add loads that can actually run together, then verify motor/compressor surge. Do not add every nameplate in the van unless they truly overlap. Load management may be cheaper, lighter and safer than a giant inverter.

DC reality

Approximate DC current = AC watts / (battery voltage under load x efficiency). A 3,000 W load at 12.0 V and 90% efficiency is about 278 A. The battery, BMS, fuse, disconnect, busbar, lugs and cables must all support it.

Idle draw

A 25 W idle inverter uses 600 Wh/day if left on. Search mode and a remote switch matter. Some appliances need continuous power, so measure the real idle state before planning.

Placement

Keep DC cables short, equal as specified and correctly fused; move the longer distance to the AC side where appropriate. Provide clearances and ventilation. Follow the inverter manual for cable, fuse, torque and neutral-ground switching.

Rule of thumb

If you cannot state the expected current, full conductor length, protection rating and manufacturer limit for a circuit, the circuit is not ready to build.

CHAPTER CHECK

• I can explain the purpose of every component covered here. • I can identify the exact manufacturer limit that controls my design. • I have added the decision, rating or measurement to my schematic/worksheet.