Use an autotransformer as a step-down to connect the 240 VAC output of a generator to the 120 VAC input on an inverter. This allows full output power of a 240 VAC generator to be used for battery charging. Autotransformers can also step-up voltage to operate 240 VAC appliances and motors from the 120 VAC output of an inverter.
DC-DC converters are used to power appliances requiring a different voltage than the battery bank supplies. For example, powering a 12 VDC appliance that needs to be run from a 24 VDC or 48 VDC battery bank. Using a DC-DC converter is preferred for powering loads that require a different voltage than the battery bank’s system voltage as center-tapping causes cell imbalances that shorten the useful life of the battery bank.
Generator Start Controls
It is very important to prevent battery banks from being discharged too far. These specialized controllers send a start-up signal to a backup or remote power generator when the battery bank reaches a given voltage set point. It is important to note that not all start controllers work with all generators. Please contact AEE Solar to assess or confirm compatibility.
Relays and Controls
The simple controls presented here enable you to automate certain functions for your renewable energy system, such as turning on/off a load or starting/stopping a generator, or inverter, based on logical conditions, such as battery voltage, time of day, or sensor reading. Relays enable a small control voltage signal to open or close a switch for a much larger voltage and current. Select relays and design your system so that it will “fail safe” if the control signal is lost.
AC input battery chargers can be used with AC generators to provide battery charging on an emergency basis or in the absence of a renewable energy source. Since proper charging is vital to battery health, a high-quality charger is recommended if you plan to charge batteries from an engine generator.
Wind and hydroelectric generators can be damaged if they are allowed to run without a steady load. Battery banks can also be compromised if they are overcharged. Diversion loads, usually resistive heating elements, are used to provide a safety load for when the battery bank is fully charged and cannot accept more energy. The diversion load is generally switched on by a controller, or relay, driven by battery voltage.