My project: Power a Beaglebone Black (BBB) entirely from solar energy. Obviously energy efficiency is crucial here. My setup so far: PV panel connected to a deep-cycle lead acid battery. Now I need to get from the battery's 12V to 5V (2A) for the BBB.
Most similar projects suggest the use of a UBEC (Universal Battery Elimination Circuit), like this one. However, I am not sure if this is the right thing for me. The efficiency curve of a typical UBEC drops pretty badly for low currents. I expect the BBB to spent most of the time idle, i.e. draw around 150 mA, which means that efficiency would be pretty low.
Is an UBEC the best solution or are there more efficient ways to supply 5V/2A(max) for my purpose? Since my soldering arts are rather limited, I would prefer a ready-made solution.
Best Answer
In terms of efficiency, this is about as good as it will get. The most efficient method of transforming the voltage from 12V to 5V is to use a buck converter as opposed to a linear regulator. The UBEC is a buck converter. For power levels in this range, an efficiency of over 90% is considered good.
If you were willing to search around for a custom buck controller IC and do some PCB design, you could potentially eke out up to 96% by selecting an IC that includes a technology called synchronous rectification. An example of such an IC is https://www.fairchildsemi.com/ds/FA/FAN2001.pdf (however note that the input voltage on this IC only goes up to 5.5V)
With synchronous rectification, you can still achieve a good efficiency at low current levels (see page 5 in the pdf). For 100mA you can still get well over 90% efficiency.