12 volt LED's good and bad how to tell before buying?

[ericmark]

Specification:

• Wattage: 2W LED
• Voltage: 10-14V dc only
• Consumption: <250mA
• Lamp: 18 White LEDs
• Light Output: >40lm

This was part of an advert for a caravan LED lamp. They actually admit it is only 20 lumen per watt where even the worst 230 volt LED lamp I have is 60 lumen per watt.

The problem is for caravans we need that 10-14V where lamps for the home are often fixed at 12 volt so using house lamps in caravans does not work. Clearly on the internet you can't see the lamp working and even in caravan shops there is rarely a display model.

To be fair the fluorescent lamps are not much better. I have measured a 16W 12V lamp and it used 20W so a standard 21W bulb in real terms used same power as 16W fluorescent. Also design has changed well know makes like Labcraft in early days had 4 connections to the tube I actually measured the voltage no tube 7 - 180 - 7 and tube fitted and running 2 - 50 - 2 volt the heaters were never turned off they just ran on reduced voltage. Latter versions did not use the heater but radio interference was rather bad on latter versions. I have not re-tested in latter years.

With the demise of gas lights in caravans having efficient 12 volt is important. One advantage with LED is failure is not sudden they start to dim before they fail.

I found some sites which did do good quality lamps 100 lumen per watt is very good.

But this one

unless they have made a mistake must be about the worst lumen per watt for any LED lamp and at £32.99 not cheap.