Autostart generators can be started by an external signal, such as one that might come from an inverter when it detects a too-low battery voltage. The control over the generator’s operation—that is, when to run and when to stop—is external to the generator, while the generator provides its own safety protection, such as shutoff for low oil level, overheating, and other factors. Among remote-start generators, the simplest is the “two-wire start,” in which a closed contact tells the generator to start and run. When the contacts open, the generator stops.
All inverters with generator-start capability can do this, as can other system components such as a manual switch, a voltage-controlled relay, a threshold signal in some system monitors, and even a signal triggered by a big load. Automatic generator operation is at best a mixed blessing. In theory, the inverter calls for the generator to provide backup charging power whenever the RE source is insufficient. However, numerous real-world bugs can interfere with such seamless operation. Automatic operation can lead to a system owner failing to perform regular maintenance, and neglecting something as simple as checking oil levels can cause catastrophic generator failure, which might not be noticed until the system shuts down due to low battery voltage.
Poor programming can lead to excessive run time and fuel consumption, yet not guarantee that batteries are adequately charged. The most likely path to eventual failure is total dependence on a generator in an unattended system.
—Allan Sindelar (from HP131)