DX protected 14500 != cold weather!!!

[Buck91]

Well I'm not sure if its the cold or the battery draw or what. I'm stumped.

I have a pair of DX Trustfire 14500 li-in I use in my cree q5 x1AA running at about 1A (battery draw) that seem to work flawlessly when handle held. But when I mount them on my bike, one will die in under 5 minutes. Granted, they usuallt see use going to the bar after dark in 0*F-20*F weather, but I would think they would last at least 10-20 minutes no?

Anybody have any ideas?

 

[mighty82]

Most lithium type batteries will suffer in cold weather. With a few exeptions i guess, because most people here think of lithium batts as the batteries than can handle the lowest temperatures (everything seems to be the opposite in the flashlight world). The kind of batteries we use in rc planes (lithium ion and lithium polymer) have very bad performance in cold weather, and has to be kept warm before using them.

I thought it was common knowledge that lithiums + cold = bad, before i started reading this forum

 

[nerdgineer]

Probably confusion because lithium primaries (lithium manganese hydroxide?) do handle cold very well.

 

[mighty82]

Yeah, didn't think of that. Rechargable lithiums are totally different from primary lithiums. So i guess rechargable lithium batteries cannot be trusted in cold conditions.

 

[VidPro]

just bring it inside with you once the device starts discharging and heating up it should make it through the cold then

i would test them in room temp and see if they even work well there

 

[Buck91]

Its works great in all types of cold when I hold it in my hand (say, working on the car or something), but it dies FAST when I use it a bike light. Very fast. My NiMH back-up handles the cold MUCH better, though its only about half as bright.

So I guess there is just no real solution to this then?

 

[Fallingwater]

Put the cell(s) in a small pouch and run a wire to the light. Keep the pouch in your pocket, or closer to your body if it's really seriously cold. Your body heat will be enough to let the LiIon cells run decently.

 

[kurni]

Put the cell(s) in a small pouch and run a wire to the light. Keep the pouch in your pocket, or closer to your body if it's really seriously cold. Your body heat will be enough to let the LiIon cells run decently.

I'm very new to LiIon; can they explode near your body?

 

[SilverFox]

Hello Buck,

This data sheet may give you an idea of what is going on. The chart only goes down to 0 C, but you can get the idea. The voltage drops quite a bit.

LG has a comment that their cells should produce around 70% of their initial capacity at - 10 C, but they don't show a voltage graph.

At any rate, if you can warm your cells before use, they should work better.

Tom

 

[Buck91]

I wonder if the temp decrease along with the voltage sag under load (1A load on cheap cells) results in in the low-voltage protection to kick in. Maybe some higher quality cells (thus less voltage drop) would do better?

 

[Fallingwater]

I'm very new to LiIon; can they explode near your body?

No more than they can away from your body, which is to say, practically never unless you drive them *really* hard, short them or don't charge correctly. And since yours are protected, I'd say it's not a risk.

 

[saabluster]

I have a pair of DX Trustfire 14500 li-in I use in my cree q5 x1AA running at about 1A (battery draw)

I think you hit the nail on the head. Cold combined with the fact you are running that 14500 very hard. I have found actual capacity of these to average 580mAh. So it would appear you are running that battery over its 1.5C discharge rating. This will cause severe voltage sag. Now add cold and you end up with a very short run time before the circuit cuts in.

 

[Gen1-4]

Its works great in all types of cold when I hold it in my hand (say, working on the car or something), but it dies FAST when I use it a bike light. Very fast. My NiMH back-up handles the cold MUCH better, though its only about half as bright.

So I guess there is just no real solution to this then?

How about putting some tubing insulation over the light after mounting it? Sounds like the air flow over the light is cooling it and that might help.