Low current from CR123 with high power LED

jlager

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Oct 17, 2016
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I'm pretty new at this stuff in general but I'm trying to power a Luxeon C Lime colored LED (https://www.digikey.ca/en/products/detail/new-energy/LST1-01H07-LME1-01/10663118) using a CR123 battery.
I was testing it with my bench power supply, giving it 3.1V with a 0.2ohm resistor and things were going great and it was pulling around 700mA.
Switch over to the CR123 battery and I noticed it was a lot dimmer. Measured how much current it was pulling and it was something like 80mA! I tried removing the resistor and immediately when connected, it now pulls about 450mA but within seconds that drops to about 250mA and it slowly keeps going down from there. If I disconnect the battery and immediately measure the battery voltage its 2.9V. It was 3.2V before I connected it.

What's going on here? Why is it not pulling more current from the battery? I tried more than one battery in case it was that but same result.
 

ChrisGarrett

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USA and Japanese CR123As are rated for ~1.5A, so what brand are you using?

New, old?

They also sag quite a bit under any appreciable load.

Chris
 

jlager

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Oct 17, 2016
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USA and Japanese CR123As are rated for ~1.5A, so what brand are you using?

New, old?

They also sag quite a bit under any appreciable load.

Chris
Energizer and new. While I was waiting for this post to get approved, I did some more testing and I think it's just the forward voltage of this LED is too high for a single CR123. Datasheet says Minimum 2.5V, Typical 2.75V and Max 3.5V. I guess under load, the CR123 drops to about 2.83V and at that voltage, it seems the LED can only pull around 200mA. I tested with a red LED and can get it to pull much higher current (around 400mA) from the same battery.

So I guess my question now is, is there a way to boost the voltage and make this work still with a single CR123 battery? I don't need very long run time if that helps.
 
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xxo

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Add a boost circuit or use a 3,2 Volt LiFePo4 cell.
 

jlager

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Add a boost circuit or use a 3,2 Volt LiFePo4 cell.
I have to use CR123 batteries for this unfortunately. I don't really know how it works but I read something about with boost drivers you lose current as a trade off? Not sure how much we're talking here.
Also, by any chance, do you know of a boost circuit for this that is already made that I can just buy? Will try to learn to make my own if needed but would prefer to just buy something.
 

xxo

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There is some loss using a boost circuit, but it shouldn't be too terrible.

I don't know of specific ones to recommend, but they are probably available.
 
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