10440 safety question (LoD-CE)

I've been reading (searching everywhere) for a real answer. All i've been able to conclude is that using a 10440 in a LOD-CE (which is my question) will over-discharge the, cell I belive. My questions...

1) I know this will kill the life span of the battery... but by how much, 10%? 50% 90% of it's lifespan?

2) I believe i've heard people running their LOD - CE with a 10440 on high, it gets hot but will this damage the battery? Will this damage the LED? CAN THIS RUPTURE WITH FLAME? (assuming proper care is taken)

3) The 10440 (ultrafire) cells are unprotected, are there any more risks involved in charging unprotected cells than regular protected cells?


I'm tring to clear up this debate, I didn't want to start a new thread but this has been staying on my mind. I really want to use a 10440 in my loD-ce that will be arriving soon but I don't want to risk my health over a flashlight and i've seen "venting with flame" videos, that doesn't help my situation.

Thanks for all your help!

Hello Shadowbuds,

Over discharge damage with Li-Ion cells depends on several factors. Some of which include, the amount of time spent in a over discharged condition, the depth of over discharge, the chemistry make up of the cell, the health of the cell before it was over discharged, and how the cell was recovered from the over discharged condition.

The worst case is that copper shunts will form and short the cell out and the next time you charge it, it will rapidly vent with flame.

The best case is that the chemical make up of the cell will only be slightly altered and you will only loose some capacity.

Heat damage to Li-Ion cells starts when the cell temperature gets over 140 F. Thermal runaway occurs at somewhere around 300 F.

A charger designed for Li-Ion cells terminates the charge when the cell gets to 4.200 volts (or lower), and the current drops to a low value. If your charger does this, there are no additional risks charging unprotected cells.

Tom

Another thing to keep in mind is that the current draw is higher than recommended for the cells -- anything over 600mA current draw will be more than recommended, and on high, this flashlight draws about 1000mA. This will accelerate the wear, but I don't know by how much. Also, the problem with over-dicharging is that this light uses a boost-circuit, as it's designed to run on 1.5V cells, so even when the cell's voltage drops to around 2.5V (time to turn it off) it will still work. It should be significantly dimmer though. If you notice the light running significantly dimmer, switch the battery out -- just don't turn it on and leave it on until it's spent, as that will completely discharge the cell and ruin it.

If you're not sure, check the voltage before throwing it back onto a charger. The time you'll get a "venting with flame" is if a cell is completely discharged, and you try to charge it. This shouldn't happen inside the light. The only time I know of where venting with flame has happened in a light is when there are two cells in the flashlight, and they are mismatched -- the stronger cell can then cause a "cell reversal" and begin to "charge up" the weaker one. Again I'd say this goes back to the point about shutting off the light if it gets significantly dimmer.

As for the light itself, many on here have been using this setup for a long time, and I've yet to hear of a light failure due to 10440 use. Considering how widely talked about this topic is, I'm sure we'll hear of it if it happens. If cells get ruined, or last for fewer cycles, that doesn't really bother me -- they cost around $2 shipped from Dealextreme -- about the same as primary AAA Lithium cells (the next-brightest option for L0D-CE), even a handful of cycles and they've paid for themselves as far as I'm concerned. (NiMH batteries will work too, they won't be as bright but will have longer runtime)

AFAIK, all available 10440 cells do not contain any overdischarge protection. Using such a cell in any light such as the LOD-CE that will overdischarge an unprotected Li-ion cell is unwise. Subsequently recharging such a cell where you may put at risk life or property other than your own is an irresponsible act. I am appalled that there are so many people on this forum that casually endorse what is an irresponsible act. Unfortunately not all potential forum readers have the good sense to ask questions such as you have before stuffing unprotected Li-ion cells in any light that gets brighter when you do so.

shadowbuds said:

I've been reading (searching everywhere) for a real answer. All i've been able to conclude is that using a 10440 in a LOD-CE (which is my question) will over-discharge the, cell I belive. My questions...

1) I know this will kill the life span of the battery... but by how much, 10%? 50% 90% of it's lifespan?

2) I believe i've heard people running their LOD - CE with a 10440 on high, it gets hot but will this damage the battery? Will this damage the LED? CAN THIS RUPTURE WITH FLAME? (assuming proper care is taken)

3) The 10440 (ultrafire) cells are unprotected, are there any more risks involved in charging unprotected cells than regular protected cells?


I'm tring to clear up this debate, I didn't want to start a new thread but this has been staying on my mind. I really want to use a 10440 in my loD-ce that will be arriving soon but I don't want to risk my health over a flashlight and i've seen "venting with flame" videos, that doesn't help my situation.

Thanks for all your help!

Click to expand...

I think there's two separate factors to the L0D CD/10440 "over-discharge" discussion; the first is drawing more current from the battery than it is rated for, the second and more dangerous is depth-of-discharge concerning the voltage that the cell ends up at after usage. You can't avoid the first issue with the L0D CE on high. You can avoid the second with vigilant usage/battery maintenance.

if you toss out the curcuit, that makes it work with 1.5v and will suck a li-ion down way to far. and replace the curcuit with the appropriate resister, that runs it at about 300ma , or 1c cfor the battery, then (done correctally) a WHITE led would take a long time to discharge the battery to low.

as long as it is designed to work with alkalines, and isnt even designed to work with the voltage of a li-ion, its just going to overdrive the led, overdischarge, and discharge to quickly

so i would do it but only after modding the light itself to death.
if you can not change all that, then wait till they make one that is designed to work at that voltage, with that current, and has a cutoff for the battery.

something like that designed to work with 1.5v you couldnt even SEE that the battery was getting to low, there would be so little indication that even if you attempted to manually cutoff, you probably couldnt determine it.

the tiny parts for the curcuit, would probably give out early anyways, had that happen before.