Helpful Tech Tips and Tricks

AC & DC Xenon ballasts. Does it really matter?


One of the most common questions about HIDs is  ‘What are AC and DC ballasts?’. We would like to get a few things straight in this article.

What is the difference?

DC (direct current) works the following way: an electrical current runs in one direction from a ballast (a power source). It uses a constant steady positive voltage in a circuit. This type of the current is distributed unevenly on the electrical components. The DC ballast moves the positive ions to the negative side only. This increases the temperature of the bulb (one side is always hotter than the other) and shortens the lifespan of the light.

dc ballast current flow
ac ballast current flow

AC, or alternative current, sends power through a circuit alternating between positive and negative voltages, as a result ,the electricity flows in both directions. An AC ballast reverses the polarity on the same electrode with the help of a reverse switch, so there is an equal distribution of ions.

difference between AC and DC ballasts

Isn’t the car battery 12V DC?

This is a really good question. The battery supplies 12V to the vehicle’s electric system which happens to be the DC power. It is all about the Xenon ballast which converts the direct current into alternative. The AC power allows to put less strain on the components of the HID light bulb while producing the same and even better light output. This type of conversion kits benefits from lower operating temperatures in addition to longer term color accuracy.

Why a DC HID conversion kit?

The main reason is its low price. The DC ballasts are very simple to manufacture since they do not need to convert the power into AC. This kit burns out faster and car enthusiasts may end up spending more money replacing the faulty parts. The AC sets require inductor coils and voltage regulators inside the ballasts to convert the current, thus these lights are more expensive on the market.

The reasons to choose AC HIDs:

  • AC ballasts do not cause fluctuations in color while DC ones are notorious for varying color temperature.
  • AC ballasts increase lifespan of the whole conversion kit.

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