I didnāt compare heat or amps or runtime, but when I compared tint of SST-20 4000K 95CRI to an XP-L HI 5A/5D, I found the XP-L HI made a much nicer-looking beam despite the lower CRI. SST-20 looked fine at high levels, but I donāt use high levels very much.
With an amc7135 chip like the D4 uses, the bottom half of the ramp stays in regulation longer with lower-Vf emitters. Basically, it stays in regulation as long as the battery voltage is higher than the emitter voltage. Then on a low battery, output falls much like it would with a direct-drive circuit. Itās a lot like a buck driver, except it burns off extra voltage instead of converting that to current.
Heat can definitely be a problem when burning off extra voltage like this, but the 7135 chips have their own thermal regulation built in. It typically works well as long as the voltage is within spec. It doesnāt work at 5V and above though, and the chips tend to die when used that way.
I stand corrected, I understand what Blue was saying now. But to poke at this a bit further, is the Vf at 0.35A really above 3V, and in the D4 now we are talking less than 0.1A per diode. Iām still thinking you are not staying in regulation on a rechargeable li-ion battery in a D4 before the voltage is so low it no longer safe to be operating. Guess it is time to investigate the Vf for an XPL-HI led.
Thanks, looks like roughly 2.74V of diode voltage for more than 0.1A of current (as the 0.35A gets split to 4 LEDs), and supposedly 0.12V across the 7135, so the light will regulate down to 3V easily at the full 0.35A going through 4 diodes. BlueSwordM is correct, but Iām guessing most of us are not planning on using batteries at less than 3V consistently.
Does it take a week to ship? I ordered a D4 last friday, and 7 days later the status is still āprocessingā. It is in stock, so is it normal or should I start to worry?
Hmā¦ Iam near to order this light with xpl ledsā¦ They dropped the price again or is it the old dropped price? The xpl version owners-whats the runtime on turbo? I got the samsungs, so probably cant get more from any othet 18650ā¦
Runtime on turbo depends mostly on the battery you use, and the level you set the thermal limit to. Thatās just how direct-drive modes work; the batteryās type and condition are a huge factor. However, in most cases, itāll still typically be under 30 seconds before the first step-down.
30 seconds to first step-down? Unequivocally? So a week (or so) ago, in the Northeast US, at ā35ĀŗF ambient and with a strong wind, the light would still step down in 30 seconds?
Oh, Iām very well familiar with where the limits areā¦ was just saying that there are variables, thatās all. Basically pulling TKās chain as it were. lol Different ambient temperatures, different humidity levels, different wind levels, a different grip on the lightā¦ a lot of things come into play as to just exactly how long Turbo will go before stepping down if it steps down at all. Sheās right though, of course, in most cases it steps down pretty quicklyā¦
