Re: Anyone running a Phillips 5761 in a FM 2" deep reflector? (now using ThrowMaster)
It sounds like maybe Beetleguise was repeatedly discharging the cells to the point that one of the over discharge protection circuits kicked in. The over discharge protection is not intended to be used this way. It is a last ditch measure to prevent the cell from being ruined in a single discharge, but over time it will still ruin the cell because the cell is discharged to somewhere in the neighborhood of 2.5V before the circuit activates. It is best not to discharge Li-ion cells below 3.0V under load on a regular basis.
Edit: The situation is actually probably made worse by the 3 stage PWM driver, because at lower current draws, the cells will discharge more fully before hitting 2.5V under load. A good measure of how fully the cell is discharged is how far the voltage bounces back. The cell voltage should return to 3.3V or higher. Any lower than that and damage is being done. This particular info was posted by Silverfox. [FONT=Verdana, Arial, Helvetica, sans-serif]
This is quoted from batteryuniversity:[/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]
"Avoid frequent full discharges because this puts additional strain on the battery. Several partial discharges with frequent recharges are better for lithium-ion than one deep one." I also found a story by someone that had stored a cell for a few months discharged to about 2.5V and it was ruined. As for my experience, [/FONT]I did discharge one of my C cells to 2.5V once and did not notice any ill effects, but I put a charge back into it in a hurry after learning more about over discharge from Silverfox and reading other member experiences. I check my cells often and recharge them when they show open circuit voltages approaching 3.6V, at which point they are almost empty. Remember, this is open circuit and not under load as with the above voltage values. If you take care of your cells like this you will not have the same problem.
If you keep discharging your cells until they are empty because you need more runtime than 25 minutes or so, then the 5761 on 2 C cells is not for you. Either switch to using larger capacity cells (or a 2s2p arrangement) or use a bulb that draws less current.
Edit: I didn't mean to come off like a jerk here... Truth be told, running the 5761 on 2 Li-ion C cells is a build that pushes to the limits of flashlight technology, and it is hard on the batteries and sometimes the bulbs. I find it likely that few people have used their AW C cells through 40 cycles with the 5761, so maybe the cells don't fair that well even if you don't run them until the protection circuit kicks in. I am glad to hear of another member's experiences, because real world data is much more useful than prattling.
