3x AAs converted to 4??

I've got a cree q5 bike light, with a remote batterypack that takes 3x AA Nimh 2500s. This is a bit of a bore as my charger charges 4 at a time. SO could I get a 4x AA battery pack and use that instead??

Thanks

J

95% of 3 cell LED lights use a simple resistor to limit current to the LED, with nothing more going on. Moving up to a 4 cell battery pack would just fry the LED.

You CAN use a 4 cell pack if you replace the resistor with a buck regulator.

Eric

hmm, if this LED is actually a Q5 the LED specs should permit overdriving to some degree...maximum input voltage is around 5, 4 alkalines is 6.. but it should sag under load

got a pic of this here light?


Some lights do not have the proper internal dimensions for a driver...is such cases I'd consider swapping the Resistor for one of smaller wattage

This is the light in question... http://cgi.ebay.com.au/Q5-CREE-LED-...temQQimsxZ20081103?IMSfp=TL081103127001r15446

In my experience here, manufactures and resellers that "claim" things like "smart IC inside" or "regulated output" or anything to that effect, while still using 3AA or 3AAA or 3C or 3D cells; are just twisting the truth. LEDs tend to have a flatter output as cells drain when direct driven because they increase in efficiency as their input power is reduced. That combined with a simple resistor, and they can pretty much get away with claiming any high floootin techno gadgetry sounding buzz words on the package and get away with it. Because there's what, like me and a handful of others in the world who might actually call them out on false advertising?

Don't trust the "smart IC" concept, assume it is a direct drive with resistor (with an additional resistor in the circuit when the "70% mode is turned on"). Assume that any more than 3 cells will destroy this light unless you determine that it does have true buck regulation that can handle higher input voltages.

A Q5 at anything over ~4.2V is getting into the instafry department. (depending on various factors).....

Smart chargers that can charge from 1 to 4 cells with individual charge control are increasingly affordable these days, and are also better for maintaining the life of the cells. Might be worth thinking about getting one?

Thanks for your help guys - I think I'll steer clear of frying anymore equipment and stick to 3x AAs Just thought, if I run 2 sets of 3 batteries, then I can charge them in a set of 4 and 2.... but also look into a charger that charges cells independantly.

Also you can see if licking your finger and touching the contacts to complete the circuit causes it to light up dimly. If so then it's just a resistor and to run 4 cells you need to change the resistor or better yet put a buck circuit.

Thanks for all this guys, I've just ordered a 4x AA charger with 4 channels, and 4 little LCD read outs - quite excited about it actually.

I've just thought, this whole lights/batteries/chargers thing is utterly addictive. 2 months ago I knew NOTHING about this sort of stuff at all. I feel I've opened a door to a whole new world of enlightenment - very strange.

When friends/family visit, I demostrate my little cree collection, and the power these things pump out never ceases to amaze people!

the typical E-Bay crap:
output and runtime cant come together,
being kind, it were 3 hours (= half of what is mentionned) at best

price seems ok for the whole package, additional shipping is ridiculously high


You would be much better off, clamping a Fenix L2D (or LD20, the new model) on Your bars and keep a 2nd set of rechargeables with You.
Thats what quite a bunch of ppl do here and that works perfectly.
As a plus one has a good small handheld light for hiking chores also.

Yellow,
You're quite right I think they calculated the 6 hour run time with the light on it's flash setting. However, I'd done my homework and realised that 3 hours would be more realistic.

The reason I went for this light in particular, is it's incredible immaculate flood, and total lack of hot spot. It throws out a huge and completely uniform circle of light. I tried biking with a Fenix torch and the hot spot drove me up the wall!
When you're rattling over rock and roots, you don't need obstacles looming out of the dark, straight into bright white light, then back into the dark again.

I've also got another focus/flood version that runs a Q4 with and 18650 that I strap to my crash helmet.

It really is wonderful light combination for mountain biking.

4 AA NIMH batteries should be ok at least they are on my LED Lenser P14 & I even bypassed the resister in the tail of the p14. It still only gets moderately warm. I still get about 3 hours of full brightness according to the naked eye. Of coarse a meter would say different but is not noticable the eye. The P14 uses the Cree XR\E Q5 LED. Don't use Lithium primary cells like the Eveready lithiums though as these will overdrive the LED.

It is still best to get a charger that charges cell independantly so they are all equally charged.

Hei JimmyG - I say change reality when ya don't like it. How about this...