The DC power source of a low frequency RFID reader must be electrically quiet with very little ripple. Some power supplies generate too much noise which causes the read range to be shorter and can cause the reader to overheat.
All power sources need to be properly sized by knowing the operating voltage and amperage requirements of the reader. The actual amperage for a particular system will vary depending on the antenna and other factors. The voltage and effective amperage is measured by the datalogger to calculate power requirements.
When setting up a new site it is sometimes easier to use a battery during the installation stage and once the system is running, measure the amperage before configuring the power source.
Batteries are an inexpensive and dependable power source. With enough batteries a reader can run for many days or weeks. Batteries are electrically very quiet (low ripple) since the electron flow is from a chemical reaction.
Solar power is a low cost power source for remote operation. A solar power source consists of photovoltaic panels with a charge controller. The solar panels are sold by wattage and a 50-75 watt system can usually power one reader. The system needs to both charge the battery and power the system during the day. If the panels will be in a valley and not get enough then more panels can be added to make up for the loss.
The charge controller regulates the power from the panel to charge the battery at the proper rate and stop charging when full, much like the regulator in a car. Many charge controllers are electrically noisy and can cause the read range to drop and in some cases cause the reader to temperature to increase. They use DC-DC conversion circuit which have oscillators to control the level which can generate noise on the power line.
It is important to select an electrically quiet solar charge controller. We recommend getting an oversized controller to minimize electrical noise at maximum sun levels. Our customers have suggested these models of charge controllers that do not cause problems for PIT tag readers.
This USGS publication gives details about building solar power sources.