How to charge inverter battery with generator?

How to charge inverter battery with generator?

You can safely charge an inverter battery using a generator by connecting the generator’s AC output to your inverter/charger’s input, ensuring the generator is properly sized (at least 1.2× the inverter’s rated power), and following a controlled start-up sequence. Modern hybrid inverters—such as Lento’s smart inverter series—automatically detect generator input, switch to generator mode, and manage battery charging with multi-stage algorithms.

Introduction

In locations with unreliable grid power, pairing a generator with an inverter/battery system creates a versatile backup solution. When the grid fails, the generator provides AC power and recharges the batteries, ensuring uninterrupted electricity. Whether you’re running a home setup, a small business, or a remote cabin, understanding how to charge your inverter battery with a generator safely and efficiently is essential to maximizing uptime and battery life.

1. Understanding the Components

1. Generator: Converts fuel (diesel, petrol, LPG) into AC electricity.
2. Inverter/Charger: A hybrid device that inverts battery DC to AC for your loads, and switches to charger mode when it senses an AC source (grid or generator).
3. Battery Bank: Typically deep-cycle lead–acid or lithium-ion batteries that store energy for inverter use.
4. Automatic Transfer Switch (ATS) or Manual Changeover Switch: Manages the transition between grid, generator, and inverter output.

Key Point: Not all inverters can accept generator input directly. Ensure your inverter/charger is generator-compatible—Lento’s smart hybrid inverters are designed for seamless generator integration.

2. Preparing Your System

2.1. Generator Sizing

• Inverter Rating: If your inverter is rated 5 kVA, choose a generator of at least 6 kVA–7 kVA to accommodate surge loads and charging current.
• Battery Charging Load: Charging at 10–20 A per 12 V battery bank (120–240 A @ 48 V) adds to generator demand. Factor this into sizing.

2.2. Cable and Connection Requirements

• Generator to Inverter Input: Use appropriately gauged, length-minimized cable (e.g., 4 AWG for up to 50 Hz, 230 VAC, 30 A) to avoid voltage drop.
• Earthing and Grounding: The generator frame and inverter chassis must share a common earth to prevent ground faults.

2.3. Safety Precautions

• Ventilation: Run the generator outdoors or in a well-ventilated area to prevent carbon monoxide buildup.
• Circuit Protection: Install suitably rated MCBs or fuses between generator output and inverter input.
• Manuals & Compliance: Follow manufacturer instructions for both generator and inverter. Abide by local electrical codes.

3. Step-by-Step Charging Procedure

3.1. Initial Setup

1. Switch Off Loads: Turn off non-critical AC loads or set the inverter to “battery-only” mode to relieve the generator.
2. Connect Generator to Inverter:
   • Ensure the inverter’s AC input selector is set to “Generator” or “External AC Source.”
   • Plug the generator’s AC output into the inverter’s generator input socket or dedicated AC IN terminals.

3.2. Generator Start-Up

1. Warm-Up Period: Start the generator and let it idle for 2–3 minutes at no load to stabilize speed and voltage.
2. Voltage & Frequency Check: Confirm the generator output is within the inverter’s acceptable input range (e.g., 220–240 VAC ±10%, 50 Hz ±1 Hz).

3.3. Initiating Battery Charge

1. Activate Charger Mode: On Lento inverters, the system will automatically detect the generator and switch to charging mode. If manual, select “Charger On” in the inverter’s menu.
2. Monitor Charging Stages:
   • Bulk Charge: High-current stage until battery reaches ~80% SOC.
   • Absorption Charge: Holds voltage constant while tapering current, topping the battery to ~95%.
   • Float Charge: Maintains a lower voltage to offset self-discharge, preserving 100% SOC without overcharging.

3.4. Load Management

• Simultaneous Load Supply: During the bulk stage, the generator powers both the inverter’s charger and AC loads. Ensure peak loads don’t exceed generator capacity.
• Peak-Shaving Strategy: If loads approach generator limit, consider shedding non-essential circuits or enable the inverter’s “Power Assist” feature (if available), which supplements generator power with stored battery energy.

3.5. Shutting Down

1. Charger Completion: Once float stage is reached, the inverter may signal “Charge Complete.”
2. Stop Generator: Turn off the inverter’s charger, allow battery to rest 1–2 minutes under float, then stop the generator.
3. Revert to Normal Mode: Set the inverter back to “Grid” or “Auto” mode to resume standard supply transitions.

4. Advanced Tips and Best Practices

4.1. Regular Maintenance

• Generator: Change oil and filters per hours-run schedule. Keep fuel fresh to avoid gumming.
• Battery: Check electrolyte levels (flooded lead–acid), clean terminals, and confirm state of health.
• Inverter Firmware: Update firmware for optimized generator-charging algorithms (contact Lento support for updates).

4.2. Automation with ATS

Invest in an Automatic Transfer Switch (ATS) tied to a generator auto-start controller and the inverter’s remote signal. This setup can:

1. Sense grid failure → Start generator → Switch AC input to generator → Charge batteries.
2. Restore grid → Switch back → Stop generator → Return to UPS mode.

4.3. Fuel Efficiency

• ECU-Controlled Generators: Modern inverter-type generators adjust RPM to match load, saving fuel and reducing noise.
• Load-Following Mode: Some Lento inverters can modulate charger current to match generator output, preventing overloads and fuel wastage.

4.4. Sizing for Multiple Inverters

In multi-inverter installations, ensure the generator can handle concurrent charger demands. Consider staggered or sequenced charging—configuring one inverter to charge at a time.

5. Troubleshooting Common Issues

6. Why Lento Inverters Excel with Generator Charging

• Seamless Source Detection: Built-in sensors detect generator AC and switch modes in under 100 ms—avoiding power interruptions.
• Multi-Stage Charging Algorithms: Precisely control bulk, absorption, and float phases to prolong battery life.
• Power Assist Functionality: Draw extra power from batteries during generator start-up or load peaks, reducing generator sizing needs.
• Remote Monitoring & Control: Lento’s cloud-linked portal lets you view generator run hours, charge profiles, and battery SOC from anywhere.

Conclusion

Charging your inverter battery with a generator transforms isolated power setups into robust, grid-independent systems. By correctly sizing your generator, using quality inverter/chargers like those from Lento, and following safe startup and shutdown procedures, you ensure efficient charging, long battery life, and reliable backup power. For turnkey solutions and expert support—covering equipment selection, installation, and ongoing maintenance—contact Lento today and keep your lights on, no matter what.