Still, let's assume that the full DC path is theoretically somewhat more efficient than the DC-AC-DC path, by perhaps 10%. So ignoring all the other factors, it is even possible that the full DC route is already less efficient than AC! At worst, if you buy one of the various adjustable buck/boost converters with wide input and output ranges, the efficiency might be considerably lower if it is operating outside of its ideal range. This conversion is likely to be, at best, as efficient as one of the above conversions.
Now consider also that the "end-to-end" DC path will generally also need a DC-DC conversion unless the device happens to operate exactly at the voltage (say 12V or 24V) of your DC system. Overall then, you're looking at a best-case loss of perhaps 15% (a 95% efficient inverter with a 90% efficient power supply) to a worst-case loss with a reasonable inverter of perhaps 40% (an inverter in the high 80s combined with a 70% power supply 2. Very small AC -> DC converters, such as those found in USB plugs tend to be slightly less efficient than converters will fewer space constraints. Some quality converters e.g., those supplied with some name-brand laptops approach 90% efficiency, but many others are in the 70% to 80% range. Very cheap or small inverters may be worse, perhaps in the low 80s and even good inverters are often less efficient when operating at very low power relative to their rated power.įor the AC -> DC side you'll find more variance. Most modern quality inverters are over 90% efficient and many approach 95% efficiency over a large part of their operating range. You have two primary conversions: the DC -> AC conversion in the inverter and the AC -> DC conversion in the power supply for the appliance. It depends on your hardware, but it's not too terrible. theġ2V car battery power is boosted to 120V by a power inverter and thenīack to 12V by the laptop's power supply)? In using a traditional car power inverter to power a laptop (i.e. Let's take a look at your first question:ġ) How inefficient is it to boost 12V to 120V and then back to 12V as When dimensioning the battery pack for your power inverter, be sure to consider your own needs and requirements, but also take into account the inverter manufacturer's recommendations.It's mostly a myth that it's much more efficient to power DC appliances like laptops on a full end-to-end DC system rather than using an inverter and then the existing AC-DC converter instead 1. In this case, car batteries are DC and they are able to power AC loads thanks to power inverters with, preferably, pure sine wave output 120V voltage. Long Story Short: Often, the most difficult questions have very simple answers.
Most 500-1000W power inverters use 12V input voltage, although there are even much more powerful units that accept 12V voltage - in order to decrease the energy losses in the wires due to the high currents, higher voltages (24V, 36V, 48V, sometimes even more) may be used, requiring connecting several batteries in series. Since most car or boat electric systems are 12V electric systems, power inverters convert the 12V electricity into the 5V (USB) and 120 volts (or 230 volts) thanks to modern electronics based on high-speed AC/DC converters that feature an efficiency of at least 80-90%. The main difference between these two is that Alternate Current (AC) changes its direction 50 or 60 times per second (mains power) while Direct Current doesn't change its direction.Ĭar batteries feature both positive terminal ('+') and negative terminal ('-'), meaning that the batteries are Direct Current (DC) power sources - yes, it is that simple. The most common DC voltages are 5V (USB) and 12V (batteries), while the most common AC voltages are 120V and 230V. Since automotive, marine, and industrial batteries are commonly used for powering both AC and DC loads, many people actually wonder if the simple car or marine battery is AC or DC power source?
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