Request suggestions on LED for project

[joema]

I want to beef up the LED in some solar-powered landscape lights I have. Just a simple little experiment. Looking for suggestions on best type of replacement LED.

The lights look about like this: http://www.siliconsolar.com/shop/catalog/Multi-Tier-Solar-Landscape-Lighting-p-51.html

During the day, a 2" x 1.5" solar cell charges 2x NiCd AA batteries. Then at night the batteries run a single white 5mm LED, which isn't very bright.

I measured the 5mm LED Vf at 3.0 volts, and drive current was 18 mA.

Is there a replacement LED that would produce more output using the same drive current and voltage?

Below is what the LED and circuit board look like:

 

[VidPro]

somone did a FULL breakdown on efficiency at specific currents, and the 4die, called other names like SMJLED, was the most lumens per watt for the 5mm things, these 4dies are a bit bluish.
so if they were run at the SAME 20ma of juice, they would look brighter, each die would only run at 5ma , high efficent.

i THINK they even beat lumens per watt, at these very low rates, high powered leds like cree and seul. i tested a cree with 20ma and its about the same.

which brings up Phosphors and how short lived any 5mm led is.
say for example these things have already run for 625 days 8 hours a day, they would be at about 1/2 power. and if they were cheap china leds, that coulda happened a year ago
http://www.molalla.net/~leeper/ledlife.jpg

if you ran a high-powered led (like a lux or cree), at such low powers, chances are good you wouldnt notice any drop in output for 10-15 years, instead of 2. so depends on what is important too, low maintance, or todays output.

then some of these lights use Colored leds, with a SINGLE color , limited spectrum, the percieved color would be brighter , but no spectrum.

good examples of that would be a CYAN , which would light plants good, and still be the SAME voltage, Turquise and cyan type leds are very bright Looking.

another example is a Yellow led, but they are different voltages, a sick yellow color would match them sodium vapor lights well

just change the pattern, the spread, the appearance, by using 3 leds instead of 1, you will run the leds lower, and more efficient, and can aim the 3.

anything else i can think of would require SOMETHING somehow, like more solar power, along with more battery storage, and mabey some adjustements in a resister. so you increase the total MA the thing can do.