Peak: Hi-Power or Ultra-Power ? Lifespan/wear

Hello,

Fact:
As you know, Peak offers the Hi-Power and the brighter Ultra-Power. Peak advises against the ultra-power and says it is only offered because of popular demand.

Question:
- Will the ultra version wear out/get dimmer sooner ?
- Will the use of rechargable NiMH cells improve the longevity or, rather shorten the lifespan ? So: if using NiMH cells in an "Ultra" will give you the same lifespan as alkalines in a "Hi" ?
- Are there any led lights that are notorious to wear out quickly ?

Thanks for any replies as these questions keep bugging me a lot.

Joris

Based on my very limited knowledge, if all other things are equal the ultra-power's LEDs would degrade sooner. This is because there is more current flowing to the LED. Depending on how much you use it, the difference may never be noticed. I do not know what the actual difference is from the hi-power. Using NiMH cells would probably make no difference, as the circuitry of the light would determine the amount of current. I'm not sure if any particular lights are considered to be prone to burnout due to overdriving.

There are many more folks here that know more and will explain it better. Stay tuned.

Geoff

First, the "ultra" vs. "high" lumen maintenance issue applies to 5mm LED lights, i.e. the Matterhorn/Shasta/Kilimanjaro/McKinley (not the ultra power versions of Peaks luxeon lights Pacific and Baltic).

What Flying Turtle said regarding higher drive current in ultras is correct (but read on regarding cell voltage). For the white Snow29 LEDs Peak uses, Chimo made lumen maintenance tests showing that they degrade noticeably faster at 40mA drive current than at 30mA. However, these are constant current tests on bench power supply, whereas the circuits in those lights apparently are *not* constant current, so the LEDs would likely not be fried after the same number of hours in a light.

My 3 LED Matterhorn ultra is about twice as bright (measured with camera) on 1.7V AAA lithiums than it is on fresh NiMH (around 1.3V). Given that overdriving LEDs decreases their efficiency, and that increased heat will decrease output as well, rising input voltage seems to rise input current *considerably* in that light (and presumably in Peak's other 1.5V 5mm LED lights, if they use the same circuit), driving the LEDs way harder with lithiums or fresh alkalines, than with NiMH or half-depleted alkalines.

A rough comparison between a high power version on alkalines and ultra on NiMH would be possible by measuring the current draw from the battery (disregarding varying converter efficiency), but more accurate lumen maintenance predictions would have to figure in the discharge curves of the batteries - a bit complicated. A more practical idea would be to just use the light and check over time whether it still maintains the same brightness on fresh batteries. Out of curiosity, I'm doing that with mine.

Anyhow, an ultra power 5mm LED would likely live much longer on NiMH than on lithiums. For typical keychain light uses, that might not matter in reality, but if you're planning to use the light for hours at a time on alkalines or lithiums, a lower power version (or an underdriven Luxeon light) might be a better choice.

I thought the runtimes were the same on the ultra power and high power models? If that's true, then they will wear out/dim at about the same time...

Hello Carrot,
Actually the runtime is not the same.
This info is from the peak website about the 3led matterhorn:
Battery Life:
Hi-Power: 3 hours 50% 12 hours total
Ultra-Power: 2 hours 50% 8 hours total

Regards,
Joris