*A bike light for UNDER R1000!!

[KlapperKnop]

I bought a light from B-L and yes initially I thought that it was rather expensive for a light ... what B-L gave me, that advice, the entire package, the pride that goes with it .... It is worth every penny!!! Thanks B-L and I hope your sales goes from strenght to strenght!!

[Azonic]

Yep. Welcome to the BL Owners club 

[Dirty Twin]

BL is the KING of light builders in SA. Dropped my bike on Thursday broke my light should get it back from BL tommorrow or Tuesday.

 

Thanks BL for great backup & service.

[Brighter-Lights]

Pleasure! That's why the mounting bracket is plastic! So in case of a bad accident, your light survives and the bracket is easily replaced.

 

 

[ZorgusPrime]

If you can't measure the output current' date=' how can you do any calculation? You need the output current for every calculation in this case.

 

Measuring the volts on the LED won't help you with anything because every LED has a different forward voltage... some are 3.6v at 1000mA and others of the same manufacturer are 4.1v at 1000mA.

 

I just published my figures because if anyone really want to compete they'll post their measurements... because I know the figures I posted can't be improved.. unless you use a heavier battery... remember... that system was quoted to be even lighter than mine...

 

You'll see that running 1 led from a high voltage, the circuit is more efficient and that the low current on the battery makes the battery more efficient.

 

Running 2 LED's in series off 7.4 volt, you'll have linear dimming before the battery pack's empty voltage (even at 350ma)

 

Running 2 LED's in parrallel off 7.4v, you will have higher current drawn and less efficient battery. 

 

I run 790mA on the LED, so devide that by 2 =  395mA each for 2 led's.

 

Cree Q5's latest batches are all about 3.45v at 395mA and 125 lumens.

 

So 2 will be 250 Lumens at 395mA with a needed voltage of 3.45v+3.45v =   6.9v nominal for the LED's + at least 0.5v for the drop over the driver circuit = 7.4v

 

So 2 led's at even a low current of 395mA will only be in regulation until the battery pack reach 7.4v - then linear dimming wil start.

 

7.4v lipo is 8.4v full and 6.6v empty.

   

[/quote']

 

 

Alright, this has been bothering me for a while, so here goes:

 

1x Cree Q5

Vf = 3.6 volts (@ 1000mA )

I   = 1000 mA

Flux = 2.2 (relative to 350mA)

Bin  = 107 lumens (@ 350mA)

Thus:

Power  = 3.6 x 1 = 3.6 Watts

Output = 2.2 x 107 = 236 lumens x 94%efficiency = 220 lumens

 

I think this is how the Revelation1 is setup.

 

 

 

 

Now what if you try this:

 

2x Cree Q5

Vf = 3.4 volts (@ 500mA )

I   = 500 mA

Flux = 1.3 (relative to 350mA)

Bin  = 107 lumens (@ 350mA)

Thus:

Power  = 2 x 3.4 x 0.5 = 3.4 Watts

Output = 2 x 1.3 x 107 = 278 lumens x 94%efficiency = 260 lumens

 

Thus you are able to get 18% more light, using less power.

 

 

This is because the output and forward voltage curves are not linear,

and the led is more efficient somewhere other than 1000mA.

 

 

 

[Brighter-Lights]

You just worked out the LED's power and the forward voltage for 1000mA is too low... most of the 30+ I have here are that forward voltage at 800mA.

 

You also didn't consider the voltage drop over a driver... and you took the same efficiency for both setups = impossible... 7.4v and 700mA is way less efficient than 11.1v and 290mA.... 

 

You can't work out the power of one LED and then just multiply it by 2... it doesn't work like that... once you put 2 LED's in series everything changes on the input side... the biggest is current which influences battery efficiency - even when using lipo's which are high current friendly...

 

You're light will only burn at 500mA per LED until the battery reaches 7.4v, then it will dim... and I've been way conservative to take only 0.5v drop over the driver... most Drivers need: LED voltage +1.00v minimum to stay in regulation - some require 1v for the driver + extra 1v per LED... that's why you can't really drive 2 LEDs off 7.4 volt at any decent current...  

 

best is to tell us:

 

Actual voltage and current over LED's

Actual voltage and current over loaded battery...

 

If you still have to build your light, I can already tell you that it will be 700mA+ on the input with 2xLED in series at 500mA each.

 

To achieve the same burn time like you stated, you will need 0.7(I)x11.5(hours) = 8000mAh

 

I've yet to see a 7.4v 8000mA lipo... but since it's 8000 and I have 4000 cells here...;-) we'll need 2x 4000cells in parallel and 2 in series = 4 cells total, which gives me a battery pack of at least 380g.  

 

The revelation-1's battery is under 290g...  ;-)

 

Of course 2 LED's at a lower current will be slightly more efficient, but not as much as you initially stated - and they'll only burn at that brightness until the battery v+ drops enough, then they will dim slowly...

Brighter-Lights2008-06-17 09:34:31

[Conti]

BL, can you mount your lights on a helmet?

if so, why dont you sent saples to the minning companies

[Brighter-Lights]

I've already made a hard hat prototype... This technology will be superb for construction, but consider incandescent bulbs and lead acid batteries vs LED and Li-Ion, then there's quite a big price difference..

 

I'm busy with home security light systems, and emergency backup light systems... Just need enough time because I'm also designing a completely new housing for the Revelation-3.

 

 

[ZorgusPrime]

http://www.thunderpowerrc.com/html/prolites.html

[Agent Orenge]

Hi BL

How is that rear light design coming along?

Rgs

AO

[floyed]

Does anyone know the power beam 5led light?

 

I would like to know how good it is and what the lumens should be?

 

oh ja will it last the transbaviaans?

[Speedi]

how much does it cost?

[Azonic]

Not allot of lumens at all... I rate those will be regular old LED's (like the kind you get in flashing tail lights), so maybe, what, 40 lumens?

[Speedi]

 

 

 

 

thats a better pic ...

 

 

 

 

 

Speedi152008-06-18 04:18:10

[Speedi]

its not a light to see with! probably 20 lumens... it costs $7

[Azonic]

I was being generous by saying 40...