Most rechargeable lights use NiCad cells. Some now use the lithium or lead acid type gell cells. The rechargeable type batteries, especially Nicads have very low internal resistence and therefore can produce higher amperage than alkaline cells. These coupled with a higher wattage bulb causes them to be much brighter but with a generaly shorter burn time before recharging. The D cells Nicads in industrial capacity are up to 4 or 5 amp capacity vs the ones from Wally World at about 1.2 amps capacity. With a known current draw from your bulb you can calculate the actual burn time from a fresh charge by dividing the draw from the bulb into the battery capacity. The low internal resistence of a Nicad is why if you put one in your pocket and your keys short it out it will burn a hole in your pants--yeah--they will--I know /forums/images/graemlins/shocked.gif. Alkaline non rechargeable cells have a high capacity but the internal resistence is much higher so they burn much longer producing a much lower amperage over a longer time thus they cannot be as bright as a quality rechargeable light.
Some of those 1,000,000 candlepower lights that can be had for less than 30 dollars actually work very well, use a 25 to 55 watt qrtz halogen. I think a 55 watt bulb of that type--H3 draws about 5 amps at 12 volts. I could be wrong about that exact number but you can see that you need either a big battery or must suffer a short burn time, one or the other.
I have a dive light I made --I built it--machined from aluminum 2024T3 billet and Plexiglass for cave diving that uses the Nicad liquid cells from the batteries that start jet turbines. These battery packs are composed of many individual cells, each about 1.2 volt but they have tremendous capacity. I run two 55w Halogens for redundancy, each individualy switched so I can run either or both. I can run two 100w bulbs as well but the run time drops to about 45 minutes. I built a few of the lights after so many wanted them and sold them for 1200 dollars but at the time I was a higly paid geologist and did not care to start a buisness--hmmm, maybe now that I am less highly paid I could revisit that idea--nah--I prefer sitting on the porch and shooting at Yankees, man o man, I can shin'em up good with that dive light /forums/images/graemlins/shocked.gif.
There is a new type of lighting system available--very expensive -- and very birght and uses very little power--HID--High Intensity Discharge. A transformer of sorts delievers power to a bulb that uses an arc rather than a filiment--like a welding torch--very bright blue light. Some cars, aircraft and special purpose lights use them. There are now small handheld flashlights but I bet they could run 400 dollars. J
