Confused about drivers?

[EL34]

I built a P7 bike light from a machined down DX P7 flashlight. see web site.
I have been testing my light using 3 x 4000 mah Sanyo NiMh batteries in series for 3.6v.

I did some beam test last night against two of my Bike HID's and the P7 light did great. see photo on web site.

http://www.el34world.com/Misc/bike/BikesLights1.htm

Now I am going to build a battery pack but I need to ask about driver boards.

I don't really care about multi modes and I can build my battery packs to include as many batteries/mah as I need since the battery packs for bikes go into water bottle cages and backpacks. I now carry two battery packs, one with 10 NiMh's and one with 8 NiMh's.

Do I really need a driver board or can I just run the light direct?

I may need to provide more info?
thanks

 

[EL34]

Hmm, no one have any advice?

Is direct drive acceptable if you do not need different power modes or can carry as many battereries as you need in a custom battery pack?


thanks, would appreciate some input

 

[gav6280]

Depends on how many Leds your running, what type they are, how long you ride for, how heavy you mind it being & how long you have or need to recharge in.

 

[Mr Happy]

Do I really need a driver board or can I just run the light direct?

Direct driving LEDs usually requires some form of current limiting. In the simplest case that can be a resistor, or even the internal resistance of the battery. If the internal resistance of the battery is used, then it requires careful matching of the battery characteristics to the light.

The danger with direct driving from a large NiMH pack is that fully charged it might provide 4.0 V with almost no voltage drop and that could damage the LED.

You probably would be better with a driver, or at least a small resistor.

You might also ask a moderator to move this question to the cycle lighting forum where there could be some more relevant experience on offer?

 

[EL34]

Thanks, appreciate the info Mr Happy

My modified P7 flashlight from DX is direct drive and uses one 18750 lithium. I looked inside the clicky switch area and there is not a driver board, just a clicky switch and a 1/2 watt 6.7 ohm resistor, which is the low power setting. That's why I was wondering about using a driver board or not.

I am ordering 4 of the 18650 2400ma lithiums from DX for the actual battery pack I will use.

I may try a couple of the 1400ma current limiting boards from DX in parallel so I can get 2800ma drive. Too bad they only sell them in packs of 10. I don't need 10 of them.

I posted here because it involves the driver board, which is the electronics. Doesn't really matter if I am using it on a bike or not does it?

Thanks agian for the info

 

[Mr Happy]

One thing to bear in mind with a "no brand" flashlight is that the engineering might not be up to the standards required for maximum durability and long life. So the construction of such a light should not be taken as a design recommendation for lighting systems in general. Most such lights will only be switched on for short periods at a time and if they fail after six months will be thrown away with a shrug. On a bike the light will run for maybe an hour continuously so that issues of heat removal, regulated current and robust design become more significant.

 

[EL34]

Ah, ok, yes and actually longer than 1 hour burn time on the bikes.

Sometimes 2-3 hours ride times at night.

I'll go the driver board route.
Makes sense.

thanks