Integrating Solar with a DC Generator
Pairing solar power with a DC generator is an efficient and reliable way to supply power to off-grid, telecom, and battery-based systems. Solar energy is available daily when the sun is present. The DC generator starts when weather or seasonal changes reduce production or when loads rise. The aim is simple: minimize fuel use, protect batteries, and maintain uptime.
Designing for efficiency and reliability
Size the solar array to cover the site’s average daily load in good sun. Size the generator for charging performance, not peak site load. Fuel economy and engine health are better when the generator runs near about 75 percent of its standby rating. At that load, combustion is cleaner, the fuel consumption per kWh is lower, and underloading issues, such as wet-stacking, are avoided. Avoid overloads that cause heat stress and nuisance shutdowns.
Control strategies: fixed voltage vs current limiting
Fixed-voltage charging runs the generator until the batteries reach their target bulk, absorption, and float voltages. Use this when the generator’s maximum output is below the battery’s safe charge acceptance.
Current limiting caps output to protect batteries with lower acceptance or smaller banks, and when solar and generator charge simultaneously. Many hybrid systems use fixed voltage as the main method with a current limit as a safety cap.
When the generator starts
Hybrid controllers can auto-start based on low battery voltage (often near 48.0 V in telecom systems), high load, or scheduled top-ups in low-sun seasons. The generator runs until the battery reaches the absorption setpoint or a minimum runtime is met, then shuts off so solar resumes the lead role.
How common are solar–generator hybrids
Solar–diesel hybrids are widely used in homes, telecommunications, and remote areas. Many mini-grid deployments utilize a solar-plus-generator combination to balance renewable energy with reliability. Off-grid homeowners often rely on generators during winter or extended periods of cloudiness to prevent deep discharges.
Battery life with proper charging
Correct bulk, absorption, and float voltages, combined with appropriate current limits, extend battery life. Undercharging causes sulfation in VRLA. Overcharging shortens the life of both VRLA and LiFePO4. A DC generator’s direct high-current charging reduces time at a low state of charge, lowers the depth of discharge, and improves cycle life.
Monitoring and remote management
Modern DC generator controllers support CANbus J1939 and often Modbus, utilizing generator controllers such as our DynaGen TG350 or TG410 models, which enable remote monitoring and control of sites. Track solar output, SOC, generator runtime, and fuel level to plan service and prevent outages.
The result
A well-tuned hybrid can cut generator hours dramatically, reduce fuel and emissions, and extend the life of both batteries and the engine. Let solar do most of the work and run the generator only when needed at an efficient load, then shut it down.