Is a Car Battery AC or DC Power Source?

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?

This time, the answer is very simple.

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AC vs. DC

Abbreviations AC and DC stand for:

- AC: Alternate Current

- DC: Direct Current

The most common DC voltages are 5V (USB) and 12V (batteries), while the most common AC voltages are 120V and 230V.

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.

Car batteries feature both positive terminal ('+') and negative terminal ('-'), meaning that the batteries are Direct Current (DC) power sources - yes, it is that simple.

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%.

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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.

Long Story Short: Often, the most difficult questions have very simple answers.

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.

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.