Electronics, Lighting, & Gadgets - What can I do about m ylight s dimming in the cold?

My Fenix LD2 and Cateye EL 530 both have dimmed on my during my regular ride home the last 2 times I've used them, and it hasn't been that cold here either. Temperatures were in the upper 40's last night, and in the mid 30's the time before that. I'm using freshly recharged batteries in the Cateye, and used both nonrechargable and rechargeable batteries in the Fenix. Both times the lights noticeably dimmed when outside, but worked much better after they warmed up when inside. I don't remember this happening before, is there something I can do to prevent this?

Well the non rechargeable batteries are most likely alkaline. Those perform miserably in cold temps, even in the 40s their performance drops off. So stop using those. As for the rechargeable batteries I am not sure. Are they NiMh, or NiCad? There are a whole lot of variables that affect their performance. Most can be traced to a poor charger. Other things we would have to know more about so we can help you would be their age, capacity, brand, and what type of charger you are using.

LEDs perform better in the cold, batteries, however perform better at warmer temperatures.

not even NiMH, NiCad, Li-I or lead-acid batteries function too well in colder temps.

I suppose you can give the entire thing a wrapping of insulation, but it can overheat and burnout the LED on hot days.

Build a headlight with some overdriven R2s mounted on the batteries ?

Sounds like a problem with your batteries. Try some higher quality rechargeables.

FWIW, I've used Fenix lights in some really cold temps (-20c) and have never had a problem.

Well the non rechargeable batteries are most likely alkaline. Those perform miserably in cold temps, even in the 40s their performance drops off. So stop using those. As for the rechargeable batteries I am not sure. Are they NiMh, or NiCad? There are a whole lot of variables that affect their performance. Most can be traced to a poor charger. Other things we would have to know more about so we can help you would be their age, capacity, brand, and what type of charger you are using.

I'm using NiMh rechargables, the LaCroose batteries that came with the BC900 charger I bought a little over a year ago. I reconditioned them on the lowest setting before I started riding after dark again, and they were around their 2400 mah rating. They had been used weekly until Thanksgiving last year when it suddenly got cold and snowed like crazy for most of December.

Sounds like a problem with your batteries. Try some higher quality rechargeables.

FWIW, I've used Fenix lights in some really cold temps (-20c) and have never had a problem.

I thought it worked a lot better last year, I've got some other batteries I'm going to try and see how they work.

your NiMH batteries are probably getting shorter life and smaller charge capacity after a year's worth of use.
plug in some new ones, see what happens.

That BC900 has a refresh function, have you tried it. Just make sure you don't need the batteries for about 3 or 4 days because that is how long it takes the BC900 to complete a refresh cycle. If that still does not improve things, then maybe your batteries are toast and it's time for a fresh set.