One of the most common questions about HID ballasts is what is the difference between AC and DC ballasts, which is better and why. Let's first look at what AC and DC is and then which technology is better.
DC, or direct current, is just that: electrical current that runs in one direction from a power source (ballasts in our case). The current stays constant and does not vary. The problem with DC is the current is distributed unevenly on the electrical components as the current is only going in a single direction. The initial portion of the electrode that comes in contact with the electrical current wears faster than the later portion of the electrode as the electrical current completes its circuit.
AC, or alternating current, is electrical current that alternates between positive and negative current. This allows for components to wear evenly as electricity is run through each component equally throughout its lifespan.
AC DC Ballast Diagram
The primary reasons AC ballasts are significantly better than DC ballasts are:
1. AC ballasts won't cause bulbs to flicker, this is a very common problem with DC ballasts
2. AC ballasts won't cause fluctuations in color, DC ballasts are notorious for radically unstable and varying Kelvin temperatures (color)
3. AC ballasts drastically increases lifespan of both your ballast and HID bulbs
This is why we have and ONLY will sell AC ballasts. They are the vastly superior technology. If you are comparing HID ballasts from other sellers, if they don't explicitly say their ballasts are AC, it is most likely they are DC ballasts. Always be sure to check which type you are getting before placing your order.