Two-Wire Dry-Contact Generator Autostart Wiring Guide: Automating Off-Grid Battery Charging
Trudging through 2 feet of snow at 2:00 AM with a flashlight to pull-start a portable generator when your battery hits 10% is miserable. Learn how to wire the NO/NC Dry-Contact Relay inside your hybrid inverter to start and stop your propane/diesel generator automatically.
📐 Step-by-Step Off-Grid Engineering & Sizing Rules
How a Dry-Contact (NO / COM / NC) Relay Works: Every serious off-grid inverter (EG4 18kPV, 6000XP, Sol-Ark 15K, Victron MultiPlus/Cerbo) has a small 2-pin "GEN DRY CONTACT" terminal block. It does NOT output voltage—it simply acts like a robot finger that closes a switch when Battery SoC drops to 15% and opens the switch when Battery SoC reaches 80%.
True 2-Wire Start Generators vs 3-Wire / Push-Button Generators: Cummins Onan, Kohler (with 2-wire kit), Generac (via Atkinson GSCM-Mini controller), Westinghouse iGen11000DFc (with auto-choke module), and EcoFlow Dual-Fuel Smart Generator support automated start/stop.
Programming Quiet Hours Lockout: Configure your inverter Gen Exercise & Quiet Hours window (e.g., Lockout 10:00 PM to 7:00 AM) and set an Evening Pre-Charge check at 7:00 PM: if battery SoC is below 35% at 7:00 PM, the generator runs from 7:00 PM to 9:00 PM so it never wakes you up at 3:00 AM!
Warm-Up & Cool-Down Timers: Set a 60-second Warm-Up delay before the inverter applies charging load so cold engine oil circulates first, and a 120-second Cool-Down delay before engine shutoff.
⚡ Conductor Sizing, Fusing & Conduit Schedule
Open Full Single-Line Wiring Schematics →- Control Signal: Inverter Dry-Contact [NO] and [COM] terminals -> 18/2 Jacketed Control Cable in separate conduit from AC power -> Generator 2-Wire Start Terminal Block (or GSCM-Mini Auto-Choke Module).
- Battery Trickle Maintainer: Run a dedicated 120V outlet or small 20W solar trickle panel to the generator's 12V starter battery so the starter battery never dies in January!
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Frequently Asked Questions: 2-Wire Generator Autostart Wiring
Can I add 2-wire autostart to a regular electric-start portable generator?
Only if the generator has an automatic choke (or fuel injection EFI) and you install a $220 Atkinson Electronics GSCM-Mini generator start controller module, which converts your inverter's simple 2-wire dry contact closure into timed choke, crank, oil-pressure sense, and kill sequences.