I would like to run my setup by some more experienced LiOn users.
I have custom cramed together a light I use every day for work. It gets used hard, but rarely abused. It is a DeWalt 2xAA. I have whittled down a light hound drop in so that it fits. Here is my potential issue. I run two 14500's in it. They are TrustFire 900mh's.
This is on me every day. I really don't want it to asplode while I am using, carrying, charging, or even the occasional dropping it.
Personally, I avoid using loose (non-pack) Li-ion type cells in series. When I do (actually it's typically packs of cells in series), I keep very close watch over their voltage, the current rate they're being drained at, and how much capacity they have. I use the weakest cell/pack as the limiting factor, and only use up to 80% of it's capacity. That isn't practical to do with lights, so I don't use Li-ion cells in series in lights.
Hi Megatrowned. The way I go about using two Li-Ion cells in series is to first, use protected cells. This should keep bad things from happening, provided the protection circuits actually work.
Rather than relying on the protection circuits though, a better habit to learn is to get a feel for how long the light will run before the cells are drained to the point where one of the protection circuits trips. Then try to shut the light down and swap cells, or recharge them, well before this point. This not only provides an additional safety margin, but also will extend the life of your cells, considerably.
Li-Ion cells discharged to the point the protection circuit trips are often actually over discharged. The protection circuit is added as a safety device, not to remind the user that the cells need to be recharged. Cells that are only half discharged each use will last many times longer than those that are fully discharged.