Cheap Front Bike Lights … Not Again … lol

[WD Pro]

Not quite …

What’s the most common / generic battery pack size for these reasonably high powered front lights ?

The ones I have seen are 4 x 18650 lithium cells in a 2x2 configuration, is this typical ? If so, is it just the cheapos that use this configuration or does it also bridge the gap into some of the more ‘quality’ makes ?

I am making a stem mounted lighting system and I just want to be sure it’s going to be a fairly universal / future proof mount

Thanks in advance for any replies.

WD

 

[02gf74]

Hmm from the led lamps ive looked at recently, mostly 3, 4 of 5 led, they are 8.4 v so 4 in series.

Not sure what you are planning to make but check out what is available. I made my first set of led lamps, oooh, 4 years ago? But the chinese are churning out better and cheaper so it makes no sense to diy.

 

[JamesM]

Re:

Hope's battery packs are all 7.4V in either 2S, 2S2P or 2S3P configurations. The 8.4V chinese packs aren't higher voltage than the Hope 7.4V packs, they are just rated differently. A Li ion cell is around 4.2V at its maximum but is nominally about 3.7V.

 

[xerxes]

Re:

The light/head units should be able to cope with a slight variation in input voltage in any case, as they are designed maintain light output as the voltage gradually drops as the battery discharges, but before it really drops off as it nears being completely discharged, so they should be fine with either 7.4 or 8.4v.

In addition, LEDs don't work in the same way as a filament type bulb, you can't just connect them to a battery, you need a driver circuit, which will include some voltage regulation. The battery voltage needs to be higher than the LEDs forward voltage, which may only be around 3 to 5v and the driver circuit will step down the battery voltage to suit the particular LED being used. Here's some more guff about that: http://www.instructables.com/id/Circuit ... D-s/#step0. Here you can see a ready made driver circuit that can cope with an input voltage from 3.6v to 16v: http://www.dx.com/p/3-6v-9v-800ma-regul ... -pack-3256

Torchy has some interesting info on various cells and chargers: http://www.torchythebatteryboy.com/p/18 ... rgers.html

 

[FluffyChicken]

Re: Re:

LEDs can just be connected to a battery just like a filament bulb.
You can select different filaments for different voltages though, but you wouldn't stick a 3V bulb onto a 7.2/8.4V supply.

Give it to much Voltage and it'll blow just like a filament bulb, gibe it too little and it'll not glow.

The only difference is if you allow an LED the ability to draw more current than it needs and it will and blow.

So really it just need something to limit the current.

All a driver (or regulator) is doing is setting the voltage and limiting the current*. Filaments work well in this way as well.

*at its basic.

The light/head units should be able to cope with a slight variation in input voltage in any case, as they are designed maintain light output as the voltage gradually drops as the battery discharges, but before it really drops off as it nears being completely discharged, so they should be fine with either 7.4 or 8.4v.

In addition, LEDs don't work in the same way as a filament type bulb, you can't just connect them to a battery, you need a driver circuit, which will include some voltage regulation. The battery voltage needs to be higher than the LEDs forward voltage, which may only be around 3 to 5v and the driver circuit will step down the battery voltage to suit the particular LED being used. Here's some more guff about that: http://www.instructables.com/id/Circuit ... D-s/#step0. Here you can see a ready made driver circuit that can cope with an input voltage from 3.6v to 16v: http://www.dx.com/p/3-6v-9v-800ma-regul ... -pack-3256

Torchy has some interesting info on various cells and chargers: http://www.torchythebatteryboy.com/p/18 ... rgers.html

 

[FluffyChicken]

Re:

Are you mounting the cells in the steerer tube?

 

[WD Pro]

Sorry, perhaps my first post wasn't well worded

I am not making the lights, I am making a universal (two) light mount that will fix to the stem and hold the lights and the battery packs

I was asking about the size of the battery's as they will be mounted to a piece of stainless, with slots for Velcro cable ties.

The lights themselves will be mounted on a 27.2mm carbon bar - formally a USE alien seat post

WD

 

[FluffyChicken]

Re:

Would look neater with batteries in the steerer ;-)

I think we just went off on chat, I think the post was clear enough. At least for me.

They are starting to make 6packs and more now.

Mines in the 4 pack config but in 3.6/4.2 volt setup. It's only powering one cree led.

 

[dyna-ti]

Amp Hour rating ?? most important

 

[JamesM]

Re:

Not on its own!!!