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Dangerboy

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Oct 23, 2006
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Having looked at the cost of 'decent' LED and HID bike lights I've decided it would be fun and (possibly) cheaper to build my own.
I've got some XR-Es and some 4 and 9 Leidl optics on the way from Cutter.
Can anyone give me an idea of what I'll need re. batteries etc?
Was planning on 2 XR-Es per light and running them at 700mA using a BuckPuck from Lumileds. Is this likely to be OK?
What batteries are best to go for- 7.2V li-ion pack/18650's/AA NiMH's?
Anyone else tried/planning something like this?
TIA
 
Yep i.e. :

7,2 4x18650 2,4 Ah battery pack + protection circuit.
1 BuckToot driver (highly efficient 85-90%)
2x XR-e's 2 optics

You will have 10 hours of constant light (160 lumens) weight under 300g.

My old project based on Cree 7090(1) leeds and L2 Optics.
xlampka.jpg
 
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Thanks, slightly confused though re. battery packs though (bear with me, I'm new to this...)
If a 18650 is rated at 3.6V, 2200mAh, then two will give 7.2V, 2200mAh.
Four 18650s would give:
14.4V, 2200mAh or
7.4V, 4400mAh
...depending on how they were wired together?
Thanks,
Adam
 
Not recommand to use Li-ion if you aren't a qualified engineer
If you not forget Sony recalling 8 Millions Li-ion Packs all over the world. The Li-ion pack is very dangerous and need highly protected.
to use AA either NiMH or Alkaline may be better, at least, you can change it anytime, anywhere you need. Besides, the cost may be lower.
 
I'm also trying something similar - my order from Cutter is on the way. I have a generator hub, and I just need an efficient rectifier to drive the led's. One of the powerpucks(?) takes AC, so I may just use that.

I'm also looking at batteries.
 
KWillets said:
I'm also trying something similar - my order from Cutter is on the way. I have a generator hub, and I just need an efficient rectifier to drive the led's. One of the powerpucks(?) takes AC, so I may just use that.

I'm also looking at batteries.
Click to expand...


Why would you want to use a relatively expensive power puck if you are running the lights from a generator? You could probably get by with a simple voltage regulator to do the job nicely for under a dollar (plus a capacitor, a few diodes and resistors); I'm no expert though.

What I see as a bigger problem is how to drop (transform actually) the 6 V output from the generator to something like 3.5 - 3.7 V efficiently. Of couse if you run two LEDs I guess you don't have that problem. If you want to add a stand light (nice feature) the circuits start to get a lot more complex.

I'm trying to put something together with one LED (Cree inside a vintage light case) and a bottle generator.

Perhaps MR AL could help here.
 
I think that safer will be put rb157 (or simply 2 shottky’s ie. 1N5818) and 1000uF 10v capacitors on each polarity - it will rise voltage to 7-8V and it's enough for standard DC driver or simple and cheap after diode put some standard voltage regulator (or resistor 😉 ) and vuala. You don't have to worry about wasted mAh...
 
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The generator is constant-current (~600ma) already, so regulation isn't required. Voltage will rise to whatever is needed, within reason.

I suppose my question should be "what is the most efficient rectifier to use"?. Efficiency on many models seems low.

BTW I also got one Ledil 10 deg. optic. The square beam looks good for mounting on a rectangular box or bar. 10 degree beam width seems to be what a lot of lights use, but I'm going to try it first before I order several.
 
I remember now -- the issue with bridge rectifiers at low voltage is the Vf of the diodes, which is .15-.45 V. for Schottky's. That hits the bottom line, obviously. There are apparently better designs, but I haven't looked into them yet.
 
Dangerboy said:
Having looked at the cost of 'decent' LED and HID bike lights I've decided it would be fun and (possibly) cheaper to build my own.
I've got some XR-Es and some 4 and 9 Leidl optics on the way from Cutter.
Can anyone give me an idea of what I'll need re. batteries etc?
Was planning on 2 XR-Es per light and running them at 700mA using a BuckPuck from Lumileds. Is this likely to be OK?
What batteries are best to go for- 7.2V li-ion pack/18650's/AA NiMH's?
Anyone else tried/planning something like this?
TIA
Click to expand...
I would go with a higher voltage pack since the 2 XR-Es will need about 7.5v just to operate normally. Either an 11.1V or 14.8v Li-Ion 4amp pack from BatterySpace.com would be sweet. (Or get a 9.6 or 12v NiMh battery pack of similar amp hour rating (about 4Ah). The Buckpuck will handle the higher voltage fine and supply the proper current to your LEDs (I'm assuming here that your Crees are wired in series)

I run my 3xLuxIII and 2xLuxV bike lights off the 14.8v, 4amp Li-Ion setup and it works great. Both use the buckpuck driver (one 1000mA and one 700mA).

So this (or something similar): http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2009
or
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2370
or
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2310
would work fine. (Not advertising for Batteryspace here, just using these as example packs that should work fine) As you run the Buckpuck with higher voltages than you need, it becomes a little less efficient.

Good luck and let us know how things turn out.
 
Dangerboy - can't wait to see how this turns out!

Battery choice is personal (and largely in my opinion charger-cost-feature limited). If you go with smaller cells (like AA), with a buck or linear regulator (not a boost), make sure to get well above the Vf (at least 1-2 volts), and more importantly, get multiple parallel cell packs (for a 7.2V NIMH AA cell pack (5), running 2 LEDs in series, you'll see a dramatic sag (dropping your current well below desired levels)... put 2x5 cell packs in parallel and that will make a dramatic difference (and be easier on the cells discharge rate).

Nice thing about AAs, they are gettting near to 3000mAh at decent drain rates (0.3C per cell typical from Energizer for instance), In a pinch you can substitute Energizer Lithium 1.5V primaries instead, which are also around 3000mAh, and can be stored with your bike light as they don't self-discharge significantly (the best alkalines will give around 1200-2000 mAh at bikelight current draws before cell resistance kills the current).

Sorry no hard advice, I'm having the same dilemma (and in the meantime running reliable NIMH. Want to also build a multi-Cree XR-E bikelight next, so eager to see others designs (the one above looks great!) Running 2 LED arrayed lights (each around total of 500mA off AA batteries) and a 10watt halogen helmet light (5x18650s at 3700mAh)
 
KWillets said:
The generator is constant-current (~600ma) already, so regulation isn't required. Voltage will rise to whatever is needed, within reason.

I suppose my question should be "what is the most efficient rectifier to use"?. Efficiency on many models seems low.
Click to expand...

Most efficient? Switched rectifier - but also most complicated, and you'll have to be careful that the driver stage doesn't use more power than you'll save.
Next in effciency would be Schottky diodes. Problem here is that the more efficient they become (i.e. the less dropout voltage they have) the more sensitive they become towards overvoltage and ESD.
Finally ordinary silicon bridge rectifiers. If chosen right for the application (i.e. current and voltage) not really that much worse thean Schottky, but more robust.

A lot of bike light builders use Schottky, I prefer silicon bridges. But then again, on one of my bikes (actually two, but the other one's my wife's) I also use a 5 Ohm series resistor in order to get the ~2.5 V needed for running the EL wire...

Bye
Markus
 
Hi!

I'm also in for building a bike light. I will use 3 Cree XR-Es on 3 2.4Ah Panasonic LiIon cells. As a driver I plan to use the MaxFlex from George (TaskLed).

My design will be to use a heatsink as a backplate of the construction, which will be fixed at the bike. On the other side, the Crees with Ledlil optics will be mounted. A plastic enclosure with a rectangular hole for the optics to shine through will protect the whole array from dirt and moisture. At the left and right side of the plastic enclosure, there will be holes for 4 superflux LEDs to shine sidewards. This is important to be seen when crossing a road.

I'm waiting now for the LEDs, Optics, Cells and the driver to arrive. Then the real fun will begin. Yesterday, I made the backlight from 25 red Leds; 5*5 in series. This works nice on 10V without a resistor.

Today, I will finish the superflux LED circuit. 4 of them will shine to each side. 4*2 in series with a resistor will be hooked on the output of the MaxFlex, which should be 10.2V (3.4V for each Cree).

Cheers,

Julez
 
nightrider said:
I would go with a higher voltage pack since the 2 XR-Es will need about 7.5v just to operate normally. Either an 11.1V or 14.8v Li-Ion 4amp pack from BatterySpace.com would be sweet.
Click to expand...
:touche:
11,1 will be nice but it is not necessarily, I spend one day testing 4,4Ah 7,2 pack with 4023-BuckToot driving 2 Cree 7090 and id what I get :

Hours 0 1 2 3 4 5 6 7 8 9 10 11
Vin 8,4 7,81 7,72 7,61 7,53 7,46 7,42 7,37 7,33 7,28 7,17 6,23
Vout 6,76 6,76 6,73 6,74 6,74 6,72 6,72 6,73 6,69 6,66 6,48 5,84
Iin 0,33 0,35 0,35 0,34 0,34 0,34 0,34 0,32 0,32 0,29 0,25 0,08
Iout 0,35 0,35 0,35 0,34 0,34 0,34 0,34 0,32 0,32 0,27 0,25 0,08
Eff 0,853535 0,865557 0,871762 0,885677 0,895086 0,900804 0,90566 0,913161 0,912688 0,851743 0,903766 0,9374

I'f ill have enough time ill test similar circuit on 700ma PowerPuck - it should give constant output 700ma in whole voltage range but it will dry out batterypack in perhaps 9,5 hurs ?
If the difference in light output between 0,35 and 0,32 A are almost imperceptible for rider I’ll use 2 more cells increasing batter-pack from 4,4 to 6,6Ah not to 11,1V. I think that the burn-time and lightweight is more crucial for night riding than constant output.
 
He's talking about using a 700ma Buckpuck (I'm assuming a 700ma 3021 or 3023). Lumileds recommends "due to the nature of the buck regulator, the input voltage must always be higher than the total forward voltage drop of the LED junction(s) connected in series (1.0V for DC models)."

2 Cree XR-Es running @ 700ma will have forward voltage of about 3.75v ea.

So in series, (2 x 3.75) + 1v = 8.5v. Below this you will not get full output with a Buckpuck.

BTW. 4400mah battery / 700 mah draw = about 6.25 hours, but in practice you'll probably get about 5 hours before diminished output (maybe less).

I like 'em bright :grin2:
 
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