How do high power li-ion incans avoid cooking their cells?

[Phaserburn]

Lumens Factory has heat warnings on their EO line of lamp assemblies, the caveat being that the heat will potentially damage the li-ion cells, not the light itself. How do lights like the Scorpion, DX lights and some others have outputs of over 300 lumens without cooking the cells? D26/D36 lamp assembly lights have direct thermal pathway between the bulb filament to the cells. Are these lights not intended to be run at more than 10 mins at a time?

I'm always looking for the best li-ion incan available that can be run without limitations for heat. Currently, that light for me is a M90 13V setup. Is there better?

Has anyone done temp readings of the closest cell to the lamp after longer than 10 minute runtimes and compared them to temp limitations as specified by the manufacturer? I love the output of LF's EO-13, but hate the runtime limitation.

 

[Phaserburn]

jeez, and here I thought this would be a hot topic...

:ironic:

 

[defusion]

it's just a warning of something that can happen.
the fact is, li-ion's deteriorate over time (loose some of their maximum capacity, so this is permanent), and the hotter the batteries get (either by outside temperatures or the bulb heating up) the faster it goes.

http://en.wikipedia.org/wiki/Lithium_ion_battery

read that, especially the bit about storage temperatures

 

[DM51]

The heat warnings are just there as a guide. If you are using a light with plenty of metal to dissipate heat, it won't get as hot as (say) a plastic/polycarbonate one (example - a Wolf-Eyes Raider would be OK where a SF G3 might not).

The cells won't be damaged unless they get uncomfortably hot to touch (above ~140F) or of course if they are being discharged too quickly (>2C for Li-Ions). You would be unlikely to get a damaging overheating problem while you are holding the light, because it would get too hot for you to want to go on holding it. You might get a problem if you left it tail-standing, and that is probably the reason for the warning. It is just there as a warning that overheating COULD occur, not that it necessarily will.

 

[SilverFox]

Hello Phaserburn,

I think we need to define how hot is HOT.

Li-Ion cells perform well up to around 140 F. When you exceed that, there is some damage done, but you are still not in danger of thermal runaway.

Thermal runaway dangers become an issue when the cell temperature gets up to 265 F, and will most likely occur if the temperature of the cell gets up to 302 F.

I am not sure a high powered lamp in normal operation would be capable of heating a battery to those kinds of temperatures. I can see temperatures in the 140 F range during high discharge tests, but that is at the very end of the discharge. If you limit your discharge to around 80% of the total capacity, you should minimize the heat build up at the end of the discharge.

Tom

 

[Phaserburn]

Hiya Silverfox. Hmm. Then the warnings issued by Lumens Factory are perhaps overstated? I can see warning against the head of the flashlight getting hot; it will, but as long as you know this, you are ok. Anyone have a rig for temp tests?

 

[leukos]

The heat warning could just be a marketing gimmick, or perhaps some part of the LA can't handle the heat?