Batteries for self build lights

[underground]

So what are folk using? I saw some stuff on Wookey's website earlier about a self built light with 2x P4 emitters in it, but couldn't work out if he meant the 'AA' bit just as a guide to the size of those 18650 li-ion batteries?

I wouldn't mind putting somthing together, but, as per previous threads by me on the subject, am a bit of a numpty when it comes to numbers, and physics.

If I needed to run a cheap self built LED light on AAs - rechargeables preferably, and didn't want to buy a drop in conversion, what emitter(s) and driver would I need to be looking at?

 

[van the man]

Hi

I have just finished building my own light based on two Cree LEDs.

I used a driver which drops the 6v output from the 4 rechargable AAs I use to power it.

I too worried about all of the physics bits and wether it would over heat etc, in the end it was all quite straight forward and the only real problems I had were;

a. where to get a battery box (canibalised off an old Zoom)

b. where to solder power input on to the driver (the back, center ring is positive)

c. blinding fellow cavers!

Hope that helps. Michiel

 

[underground]

Definitely helps! What does the driver drop the voltage to? I looked at 2 Cree XR-E R2 LEDs and got the impression they'd need more volts than the 4x AA batteries would provide - i.e. they seem to need 3.7V so running two would need nearly 8V, wouldn't it?!

This is the sort of thing I'm getting tangled up with...

 

[SamT]

Ah -

If you wire them up on 'parrallel'  - they will only require 3.7 volts. But your battery will last half as long.

If you wire them up in 'series' - they will requre 7.4 volts to shine as brightly.

(at least I think, since they are not simply 'resistors' like a normal filament bulb, but Diodes. so not sure if the above applies  ).

Adding to UG's question..

These "drivers" that everyone talks about. What are they exactly. Im guessing a little chip or something, that can be programmed to give the various settings that many of these lamps have, i.e. blip once for full power, twice for half power etc etc.

so how are they programmed then ??

I can do a bit of electronics, in theory, but I still remain baffled by these drivers. Guess I need to get my hands on some and start tinkering.

 

[van the man]

In my setup I have only one Cree working at any one time, ie one is a flood mounted near the front of the enclosure and the other a spot mounted at the back of the enclosure behind a lens.

Sam, to the best of my limited knowledge a driver is a voltage regulator and can be either a 'puck' or a 'buck'.

Buck reduces the voltage to the standard 3.7 a Puck increases it. I think that the different modes available on some are cheap USPs

Again hope that helps and sorry if it is compleatly wrong but it worked for me!

 

[footleg]

Many drivers are in fact current regulators. So they automatically adjust the voltage across the LED so that the current (measured in amps) remains constant. These sorts of drivers are usually specified in terms of the current they deliver, so you need to match the maximum current quoted for the LED you are going to use with the driver.

e.g. I have made some P7 lights. The LEDs are specified as taking a maximum of 2800mA (or 2.8A, same amount as 1000mA = 1A). So I chose a driver which delivered 2.8A maximum current. I say maximum because these drivers, like many others have various power levels. You can switch between the power levels by simply turning the light off and on again quickly. The different power levels allow you to run the LED at different brightness levels. Just make sure the maximum power level of the driver is not greater than the maximum the LED can handle. It is OK to chose a driver which outputs less current than the LED can handle. It will just be less bright. This can be desirable as the battery life will be longer, and the LED will get less hot.

Heat is one of the main problems. The LED needs to be in contact with a metal plate to take the heat away and get it out of the case. Lights like the Scurion are made of metal to do just this. Even there, the P7 LED is only run at around 2/3 of the maximum brightness it is capable of, because it would over heat otherwise.

 

[Agrophobic]

Running two p4's off AA's- hmmmm, if you use 4 AA's then you'd need to either run two drivers in parrallel each driving one LED, (this is a good setup cos you can switch them independently, BUT running both at once will flatten your AA's pretty quick, like an hour or so) or use one driver to run 2 LEDs in parrallel which will only give you half brightness to each LED.
If you use one driver and 2 LEDs in series you would need 7 AA's as you need a shade over 7.4v cos the driver needs a bit. fine if you've got the space and holder to take them.
From past experience i'd recomend using two drivers in parrallel +two LEDs and running them from four 18650 li-ions in what is called a 2p2s arrangement where you parrallel 2 cells and connect them in series with another parrallel pair. this gives 7.4v at double the capacity of one cell. the driver happily drops 7.4 down to 3.7v. just make sure you use a battery protection pcb designed for this arrangement, individually protected cells will give you trouble if you build packs with them. you can get round this by charging them independently but its a PITA.
Hope this helps you.

 

[SamT]

cheers footleg..

another thing...

Can someone list the common types of LED's used in the various lamps, scurion/sten etc.
. we constantly hear - P7, P4, R2,  CREE, LUXON etc. but I bet they are all just made by the same few companies. a quick list of the commonly used LEDS, the company, a rough price and an example of a lamp they are used in.
Listed in ascending order of brightness (but lets not get into the vagaries of whether some a 'actually' brighter than others.

eg...

P4, by Cree, 3 quid used in a sten
R2, by Luxon, 10 quid, used in scurion -


(am I asking too much - it will benefit us all).

 

[potholer]

High power LEDs by company:

Company - Lumileds:

Luxeon I, III, V - First-generation high power LEDs. Now largely obsolete

Luxeon K2 and Luxeon Rebel - More recent (and more efficient) than the earlier I/III/V, the K2 is in a similar-sized but different package to the earlier LEDs, the Rebel in a much smaller footprint.


Company - Cree
XR-E. Often referred to by the efficiency-rating codes, of which the most common are, in increasing order P4, Q2/3/4/5, and R2

MC-E - Basically 4 XR-E-class 'dies' in a single chunkier package


Company - Seoul
P4 - largely similar to the Cre XR-E, with shared technology, but in a different package.

P7 - Basically 4 P4 dies in a single chunkier package


As far as power->light efficiency goes, excluding the Lux I/III/V, the best performing versions of all the others mentioned above are in the same ballpark, with the best Crees being a little ahead, but not by a great margin.
Price-wise, there isn't a great difference either, with the K2/Rebel/XR-E and Seoul P4s all being roughly comparable. Apart from at the very cheap end, these days the LED cost isn't a great part of a product price.

 

[SamT]

kerching..