The voltage should be the same. Cigarette lighter is just constant battery voltage (direct Terminal 30) and flash light is activated on ignition position 1 (via ignition switch to Terminal R rail).

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E39 530dA -02 M-Sport Messing metallic
E53 X5 3.0dA -06 Sport Stratus grey
E70 X5 40d -12 M-Sport Space grey