Many industrial solar system designers are faced with the issue of power systems needing to supply both 12 and 24V loads. Though SCADA systems are available with either voltage, issues arise when equipment of differing DC voltages is incorporated into the same system, for example 12V radios and 24V sensors. The solution includes the addition of a DC-DC converter (available in a variety of ampacities) to make all of the loads the same voltage to match the battery system voltage.
Here’s some ideas about designing a power system that provides two output voltages:
1. Select the battery voltage for the higher of the two voltages, typically 24V over 12V, as downward DC-DC conversion is easier than upwards. Click here for DC-DC Converters. If the 12V power draws are more significant than the 24V draws, you can use a 12-24V DC-DC up-converter.
2. Calculate your total loads carefully, with the goal of finding the daily total power consumption. A typical DC-DC converter is 88% efficient, and delivers power at a constant 13.8V. Find the current draw (in amps or milliamps) for the 12V loads, multiply by 13.8 to get watts, factor in the duty cycle of the 12V loads (if they are variable like a radio), then divide by 0.88 to arrive at the daily total needs of the 12V loads in watt-hours.
3. Add the 12V loads to the 24V (in watt-hours per day). This number is used to determine which solar panels to use. Note that 24V systems usually use two modules wired in series. Sizes include 50, 85, 125, and 150W. Each 100 watts of solar can safely maintain a daily load of about 120 watt-hours in December in Alberta.
If this is overwhelming, just bring your project to the HES sales support team. We have decades of experience and can advise you on the appropriate solution for your specific application. Contact our sales team for assistance.
Stay tuned for more solar design topics including variable loads, mounting options and the effects on output, charge controller technology options, and more. Or submit your questions to: firstname.lastname@example.org.