What's the Difference Between Bi-Xenon and Normal Xenon?

The difference between bi-xenon and normal xenon

Customers regularly ask us what the differences are between normal and bi-xenon. So we took the time to write a page about it.

The biggest difference between bi-xenon and the normal version is that with bi-xenon you get both low beam and high beam in xenon light. In most cases this uses a special bulb that changes its focal point in a split second by means of a magnetic switch. (There is also a duo H4 bi-xenon bulb, which we've left out of our range for practical reasons.) We'll take the H4 bi-xenon bulb as our example, because it's the most common one.

Bi-xenon vs normal xenon: 3 types of H4 bulb

1. "Normal" H4 xenon bulb: this has 2 bulbs on the fitting. The big long one is the xenon bulb that handles the low beam, and the small one is a halogen bulb that handles the high beam. (We no longer stock this bulb because of its higher chance of stray light.)
2. H4 bi-xenon bulb: this has 1 bulb on the fitting. The big black part at the bottom contains a magnet that switches the bulb from low beam to high beam in a split second. (best seller)
3. Original H4 incandescent bulb: the bulb that was fitted as standard if your car didn't come with xenon from the factory. This bulb has a low beam filament and a high beam filament.

Connecting bi-xenon

On top of that, an H4 bi-xenon kit always comes with a special relay cable that connects to the battery on one side. This cable lets the bi-xenon bulb switch between low beam and high beam when you flash your lights or turn the high beam on. Normal H4 xenon kits connect the normal way, with no cable in between.

Which cars and motorbikes have an H4 headlight?

An H4 bulb combines low beam and high beam in one bulb, with two filaments. You'll mostly find it in cars and motorbikes with a single bulb per headlight for both functions. If your car has separate bulbs for low beam and high beam, you probably have a different fitting, such as H7 for low beam and H1 for high beam.

Here's how to recognise an H4 bulb:

• The bulb has three contact pins on the bottom: one for low beam, one for high beam and a shared earth.
• Inside the glass you can see two filaments, one of which has a small shield underneath it.
• The base of the bulb says H4.

If you're not sure, check your car's manual. Besides H4, there are other fittings that put low and high beam in a single bulb, such as H13 and HB5. Bi-LED bulbs exist for those fittings too: have a look at the LED low beam and high beam bulbs or read the car LED lighting buying guide.

The H4 bi-xenon bulb Hilox Evolution: specifications

Our range includes the H4 Bi-Xenon Bulb Hilox Evolution. According to the product data:

• Wattage: 35W
• Light output: 4,200 lumens per bulb
• Operating voltage: 11 to 30V
• Lifespan: 3,200 hours
• Use: low beam, high beam and fog light
• Glass: anti-UV quartz tube from Germany, with UV protection shield
• Xenon gas: APL metal halide from the United States
• Electrode: Plansee from Austria
• Double-shielded wiring

Please note: according to the product information, this bulb has no ECE approval or Dutch E-keur and is not intended for public roads, but for circuit and private land use. You'll find other standalone bulbs under xenon bulbs.

How the relay cable of a bi-xenon kit works

With a normal H4 halogen bulb, the car simply switches between two filaments. A bi-xenon bulb has just one light source, which stays lit all the time. To go from low beam to high beam, a magnet in the base nudges the bulb a tiny distance. That changes the focal point in the reflector, so the light reaches further.

That magnet needs its own stable power supply. This is why an H4 bi-xenon kit comes with a relay cable that connects to the battery on one side. The cable uses the car's high beam signal as its control signal: when you turn on the high beam or flash your lights, the relay switches the magnet on.

When connecting it, make sure of the following:

• a good, solid connection to the battery;
• cables that don't run along hot or moving parts;
• a test of low beam, high beam and flashing before you tuck everything away.

After fitting, have the beam aligned and check that your car still meets the MOT requirements (APK, in the Netherlands). If you're unsure, ask the RDW or your inspector.