This was not an easy light to build; not because it was difficult to assemble, but because it was difficult to obtain all of the parts. I have been working on this light for about a year. The holdups with this build are the D size Li-ion batteries, of which only 300 were ever made about 2 years ago, and a suitable regulating circuit to prevent instaflashing the bulb and driving it too hard.
With 14.4V from the 4 Li-ion cells, my AWR hotdriver can't handle dropping the bulb voltage down to 12.48 (IIRC) without frying the FET, so two tailcap resistors help by dropping about 1V with 9.3 Amps of current flowing through them. Thermal grease carries the resulting heat to the tailcap.
Since the D size Li-ion cells are unprotected, extra care must be exercised whenever handling, charging, or discharging them. To that end I also soldered a 10 Amp automotive style plug fuse into the tailcap in case the light develops a short.
This light gets extremely hot in operation, so the hotdriver circuit must be configured with the optional high power thermal shutdown option. The high power option also uses an FET with greater power handling capability. There is also a slightly different build up required for certain bulbs such as the 62625 in that they need the KIU socket to be set at a different height. The circuit overheats in something like five minutes of continuous operation without insulating it from the heat with ceramic insulation behind the reflector. I am using a 1/2" ceramic blanket material.
Of course, the stock lens and reflector must be replaced with borofloat glass and aluminum respectively, and since the 64625 produces a beam with many artifacts otherwise, the use of a stippled reflector is recommended. This light is not optimized for throw, but can light up everything for 300 feet in front of you. I like a #6 stipple (medium stipple) from Litho123.
Lights in this class are a responsibility and should be treated like loaded weapons, which is why I never store the batteries in the light. I built a PVC battery carrying tube for transportation and storage. Not only will this light start fires, but I would hate to see someone burned or with permanent vision loss because of carelessness. On this note, charging the largest Li-ion cells ever made should be of utmost concern, because it is overcharging that will result in a violent reaction aka explosion. I am building my own 2 Amp charger which is discussed in
this thread, but if I had the money I would like to invest in a Triton or Schulze or similar versatile charger. The last thing I would use is an Ultrafire WF-138 or WF-139 because they are known for overcharging unprotected Li-ion cells, and I have noticed that larger capacity cells tend to overcharge to a greater degree with these types of chargers. I charged one of my D cells with a DSD and came back for a voltage check to find it up to 4.22V and still charging. The same charger does not overcharge AW C cells, AW 18650s (both protected) or unprotected Sony 17670s. These cells should be charged individually and always monitored for voltage balance before and after runs. The hotdriver will automatically shut the light off when the input voltage drops to 90% of the set voltage, so this setup does have some measure of overdischarge protection.
