The H7 is a single-filament halogen bulb operating at 12V and 55W, fitted with a PX26d base. It conforms to ECE standards and holds approval for use in Europe, worldwide markets, the United States, and Japan.
The D5S is a high-intensity discharge (HID) xenon bulb operating at 12V and 25W, fitted with a PK32d-7 base. It is classified as a low-voltage compact type and conforms to ECE standards for Europe and worldwide markets.
On the Audi SQ7, the 2021 model year offered two distinct headlamp configurations: a halogen system and an HID system. Each configuration uses different bulb types across both high and low beam positions, making the headlamp system type a critical factor before any bulb replacement.
In the 2021 SQ7 with halogen headlamps, both the high beam and low beam positions use the H7 bulb. In the HID configuration for the same year, both positions use the D5S bulb.
For the 2023-2024 SQ7, the high beam position specifies the H7 bulb, while the low beam position specifies the D5S. This means both bulb types are present simultaneously within the same headlamp assembly.
The D5S draws 25W compared to the H7's 55W. Despite producing significantly less wattage, HID technology generates considerably higher luminous output, which accounts for its use in the low beam position on later model years.
The H7 and D5S use physically distinct bases, PX26d and PK32d-7 respectively, and the two bulb types are not interchangeable with each other in any position.
The D5S base designation PK32d-7 is specific to the D5S type and is not shared with other common HID bulbs such as the D1S or D3S, which use different base configurations. Cross-substitution with other D-series bulbs is not supported by these specifications.