LittleBill
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Anyone know why the run times are so different between these 2 lights? same emitter and same lumens, yet a serious difference in run times...
Fenix PD35 vs UC35 Runtime differences
- Thread starter LittleBill
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There are several versions of these lights. Which are you comparing?
Until the most recent versions, these lights used timed stepdowns. Some of the runtimes I've seen advertised for the PD35 suggest they're resetting it to max output every time it steps down, producing a shorter runtime (just over an hour). If allowed to just do its thing, an older PD35 will step down twice and run for about 4 hours at a much lower output than it started.
Recent models are using active thermal regulation. They're not doing a very good job of it, as there's lots of ringing (oscillation around an average value instead of actually settling to that value). It's even shown on the graphs Fenix is now putting on their product pages and packaging. Lights with this are typically advertising the runtime if it's just turned on and left alone.
Until the most recent versions, these lights used timed stepdowns. Some of the runtimes I've seen advertised for the PD35 suggest they're resetting it to max output every time it steps down, producing a shorter runtime (just over an hour). If allowed to just do its thing, an older PD35 will step down twice and run for about 4 hours at a much lower output than it started.
Recent models are using active thermal regulation. They're not doing a very good job of it, as there's lots of ringing (oscillation around an average value instead of actually settling to that value). It's even shown on the graphs Fenix is now putting on their product pages and packaging. Lights with this are typically advertising the runtime if it's just turned on and left alone.
LittleBill
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the V2 versions, and i am looking based on the charts etc. yea the step downs are a bit new to me, i learned after my HP30R about the thermal activation.
that said the v2 versions appear practically identical, so i don't know why the run times are so different its pretty significant. and the pd35 is smaller so i would think it heats up more, but no idea, was hoping fenix would respond in theire manufacture thread.
that said the v2 versions appear practically identical, so i don't know why the run times are so different its pretty significant. and the pd35 is smaller so i would think it heats up more, but no idea, was hoping fenix would respond in theire manufacture thread.
Power Driver
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The UC35 V2 has slightly more throw and a tighter/more concentrated hotspot. I'm sure that plays into the lower runtimes compared to the PD35 V2.
The emitter and advertised output are the same, which would result in the same power consumption. If the throw is actually different (as advertised), the difference would likely be in the reflector and not significantly impact runtime.
Look at the graphs Fenix provides.
UC35:
PD35:
The UC35 stays in regulation much longer before output starts to drop below the thermally-regulated average. That's why the runtime is shorter. The same can be seen in lower modes; the PD35 falls out of regulation, then loses output gradually while the UC35 stays in regulation until what looks like a deliberate low-voltage stepdown.
Look at the graphs Fenix provides.
UC35:
PD35:
The UC35 stays in regulation much longer before output starts to drop below the thermally-regulated average. That's why the runtime is shorter. The same can be seen in lower modes; the PD35 falls out of regulation, then loses output gradually while the UC35 stays in regulation until what looks like a deliberate low-voltage stepdown.
LittleBill
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The emitter and advertised output are the same, which would result in the same power consumption. If the throw is actually different (as advertised), the difference would likely be in the reflector and not significantly impact runtime.
Look at the graphs Fenix provides.
UC35:
PD35:
The UC35 stays in regulation much longer before output starts to drop below the thermally-regulated average. That's why the runtime is shorter. The same can be seen in lower modes; the PD35 falls out of regulation, then loses output gradually while the UC35 stays in regulation until what looks like a deliberate low-voltage stepdown.
yea i noticed that after i went back to the graphs, makes sense, just surprised they would change it that much. I ordered the UC35 hope its a nice upgrade from my ld22 and fits in my back pocket ok.
but yea the games are bit annoying my HP30R has both active thermal management and timed drop downs, makes it difficult to really compare lights in regards to upgrades, then my CL30R apparently doesn't have thermal regulation. LOL makes your head spin,
this is a big jump from my AA series of lights to all of these 18650 lights. but the built in USB charge port is actually more versatile, then a bunch of enloops and a stand alone charger, also the fuel gauge is better then waiting for my AA lights to drop light modes to realize the battery's are dead.
Last edited:
CelticCross74
Flashlight Enthusiast
this is very interesting! I have yet to actually compare the ANSI numbers for the V2s right next to each other like that. I have the V2 PD35 and love it. Looks like the V2 UC35 just proved itself different enough to get...
@zak
Thanks for your very detailed answer.
Undecided between UC35 V2.0 and UC35 V2.0 I bought the PD35 but when I looked at the technical sheets before buying I asked myself the same questions that I see in this thread.
Undecided between the two Fenix I bought the PD35 V2.0
I must say that I'm happy with the PD35 V2.0, I don't like the fact that I have to use button top batteries and I would have liked a more powerful High level (at least 400/450 lumens instead of 350) but at the turbo level this light is fantastic.
Since the first day I thought that it had a throw higher than the declared one, tonight I tried the luxometer, with PD35 V 2.0 I get a peak of 18300 cd (declared ANSI 15600) and after 1 minute it still has 17400 cd.
Encouraged by this today I also ordered the UC35 V2.0 I hope it is performing as I have seen on various youtube reviews where the two lights compare, everyone says that the UC35 has a higher throw.
I have read many complaints (UC35) about the mode button that falls out but it doesn't seem to happen to all users.
The firefly level and a declared throw of 17700 cd seems interesting tomorrow I can say something more.
I thought maybe I get some more lux because I use unprotected batteries (Sanyo GA)
If so, the UC35 could reach 19000/2000 cd
Tomorrow I can say something more and maybe in the following days do a runtime test between the two lights using two Sanyo GA
