TRS Tech

Technology: HID Ballasts Explained

Ballasts are necessary to turn on and run the HID gas discharge bulbs. They use a series of capacitors in an igniter to fire up the bulb with 25,000 volts of electricity, and then regulate power usage back down to less than that of a typical halogen bulb. Today, most ballasts have the igniters integrated into the bulb socket, whereas a lot of oldschool ballasts have external "standalone" igniters. There are a variety of designs produced by OEM and aftermarket manufactures, but we choose to only offer ballasts with integrated igniters because they're more retrofit friendly.

The more expensive OEM ballasts such as the Matsushita Gen 3's will not make your headlights any brighter than a less expensive aftermarket ballast. There is a good margin of quality between good OEM and really cheap aftermarket HID kit ballasts though, mostly in terms of long-term reliability. OEM ballasts also tend to warm the bulbs up to full operating intensity a few seconds faster than aftermarket units as well. Fortunately, the company that produces our Morimoto ballasts allows us to name our own price and thus the level of quality. Yes, they are a bit more expensive compared to the $50 eBay special ballasts, but that's because we're paying more for them in the first place. One quick giveaway that our ballasts are different than most aftermarket units is that they come pre-configured with D2S sockets for the bulbs. 99% of aftermarket ballasts out there come with what's known as "AMP" connectors for compatibility with rebased HID bulbs / HID kits. Eliminating this connection alone enhances the reliability of our aftermarket 35w and 55w ballasts.

One downside to OEM vs. aftermarket ballasts is that the OEM ones typically are not as "waterproof' as the aftermarket units. This is because they're usually mounted half inside a headlight assembly when they're spec'd OEM. Aftermarket ballast manufactures know that their ballasts will be exposed to the elements, so they're typically designed with fully sealed casings. Again, our Morimoto ballasts are not only externally sealed from the elements, but they're "potted" internally and will literally run even submerged in water.

Looking for a brighter output? One way to make your bulbs burn brighter would be to select 55w high output ballasts. All OEM applications use standard 35w units, but if you're a retrofitter looking to put the most possible light on the road, then these ballasts are for you. 55w bulbs are also available, and highly recommended for use with these powerful ballasts. You can use 55w ballasts with standard 35w bulbs, but the life of the bulb will be shortened, and there will be increased heat. All OEM applications use 35w ballasts, and when coupled with a high performance projector, you'll really be putting plenty of light on the road anyways. TRS usually does not recommend using 55w ballasts.

On top of wattage, Ballasts can also be categorized by the kind of bulbs they're designed to use

Ballasts designed for use with D2S/D2R bulbs

The igniter is part of the ballast system. The most commonly used kind for retrofits because the best projectors use D2S bulbs.

Ballasts designed for use with D1S/D1R bulbs

The igniter is part of the bulb, so it is not part of the ballast system. Becoming more common in OEM applications, but not widely used for retrofitting because projectors that use D1S bulbs lack in performance.

Ballasts designed for use with D4S bulbs

A new generation of mercury-free HID bulb technology is on the rise that requires the use of special HID ballasts. Relatively rare still (only found in Toyota vehicles) but will likely become more popular. These setups are not only brighter compared to other 35w setups, but are more environmentally friendly as well.

Our recommendation for retrofitters

Morimoto 35w slim ballasts to get the most bang for your buck- they offer great reliability, resistance to the elements, and a nice mounting system. If you want something that looks and feels expensive, but won't make your headlights physically brighter, the OEM Matsushita and Mitsubishi units are where it's at.