Hi all,
Long time lurker here, finally posting as I need some help with selecting the right driver for my convoy S2+.
I am intending to buy 2 Convoy S2+ to use as bicycle lights. The lights will probably spend 70% of their life in strobe mode, and the other 30% in high mode.
What kind of runtimes can I expect on (a) strobe and (b) high with 7135*4 & 7135*6 drivers?
Thanks.
Using a good 18650, such as a Sanyo 2600mah, you can expect the following from 7135*6:
High mode draws 2100mA = 74 minutes (strobe would probably be around double)
Medium 840mA = 3.1 hours
Low 105mA = 48.8 hours
I’ve ordered a 7135*3 and I’ve estimated the following:
High 1050mA = 2 hours 47 minutes
Medium 420mA = 6 hours 2 minutes
Low 52.5mA = 49.5
Run time≈real battery capacity / current.
From the website:
7135*3 output current 1050mA
7135*4 output current 1400mA
7135*6 output current 2100mA
7135*8 output current 2800mA
Modes used from Convoy are 100, 30, 5%.
So using the Run time≈real battery capacity / current formula makes it easy to estimate the overall run time in each mode. Strobe is usually about double the high mode.
Thanks for the explanation Dave.
Given those figures I’ll probably stick to the 7135*4. On a bicycle runtime is probably a little more important to me than a few extra lumens.
Cheers
You’ll probably be well satisfied with the 7135*4 version. With the 7135*3 you can expect 500 lumens which is a pretty good amount. If you’re using it on strobe for the bike you’ll definitely be seen. I do the same on my bike, I have one on strobe and the other on constant. Same with my rear lights, one on blink and the other on constant.
Enjoy! 
What environment are you riding in? City? Suburban? How is the street lighting?
I have had two S2's on XM-L2 U2-1Bs with the 8*350mA 7135s on mid mode (1.13A measured) and they've held up on a 3-4 hour ride before stepping down with the low voltage warning. Using Sanyo UR18650FMs tested to 2200mAh~2300mAh.
Watch out while using the strobe mode, the programmed strobe mode in the Convoy's IMHO are too fast for bicycle use and it annoys oncoming traffic even while pointed to the ground :stare: (from first hand experience).
Because you're getting a pair of S2+'s might I suggest throwing a Carclo 10197 in one of them? It gives me a nice wide beam.
@Otanacious - Point taken about the strobe - I guess I never really considered that too much. I’ve been using a SWM V10A which is nowhere near as bright as an 18650 light would be. However most of my riding is done during the day though, so hopefully the 18650 doesn’t prove to be overpowering, especially when dipped down so that it doesn’t shine directly at oncoming traffic.
Interesting about the Carclo lens - that looks rather handy for a bike light. Will look into it!
Thank you.
I have two Cateye HL-EL135Ns that are on blinking mode while I ride during the day for oncoming traffic visibility, so I think using the strobe on the S2+ during the day would be ideal, but care to point it down once the sun starts to set.
As for the 10197, after reading garrybunk's thread on diffusing techniques I definitely wanted to have a 30*60 wide beam. If you're in the states, LEDSupply has them for $1.25 shipped w/ tracking, otherwise Intl-Outdoor has them in a 2-pack for $2.65.
Thanks Otanacious. Ordered the S2’s and the 30*60 lens. For $2.65 for two of the lens - it’s worth trying.
Safe riding!
If I’m not mistaken the S2+ is an 18350 light, if so run time will be considerably less than if the 18650 S2 were used.
It comes either as an 18650 or an 18350/16340 variant.
I bought the 18650 version ( at least I hope so! )
Edit:
18650
18350/16340
Ah, I didn’t realize it was available as an 18650.
That’s basically correct, but drivers are rarely 100% efficient. Typically high will be the most efficient mode, but it still isn’t perfect. I usually use this formula, then multiply by 0.85 or 0.9 to calculate 85% or 90% efficiency.
Excellent, thank you. I’ve noted this for future reference as it will come in handy as I get farther into modding
Different drivers have different efficiencies as well. Linear drivers (like these 7135 based drivers) are more efficient, but the PWM in the lower modes reduce efficiency a bit. Boost/Buck drivers are less efficient, typically 70-80%. Just change the coefficient depending on the driver you are using.
I’d imagine that (battery capacity / current draw * factor) also has to take into account when the light or battery cuts off due to protection. Most of my lights shut off around 2.9v - 3v so any remaining battery capacity is useless. However I’d guess that the remaining amount is too small to be noticeable.
True. Some batteries also have reduced capacity when run at high currents.
I would add that for high-current drivers (6-8x7135) runtime will probably be longer than estimated by the formula.
Only a fully charged battery will normally be able to provide say 2.8 amps, so during a large part of the dischagre cycle it will be working at lower currents thus reducing brightness and increasing runtime. For 4*7135 this effect is already negligible, I guess.
Those lenses fit inside the s2+?
Instead of the reflector?