Driving 4x R2 LEDs from 7.4V ?

[MrNaz]

Looking for suggestions on how people would power 4x Cree XR-E LEDs from a 7.4V LiIon pack. If the number of LEDs and Vbatt are not changable, what are my options?

 

[allburger]

The easiest way is to run 2 loops of two in series.

 

[monkeyboy]

I've built 2 lights with this setup. I would wire LEDs in series and use the fatman driver. The shark driver seems to have overheating issues with this configuration.

 

[Packhorse]

Use the Kai Domain driver and run all 4 in parallel. 700ma each.

I have done several lights like this. I have also done one running 2P2S off the same driver but you need to up the voltage a bit.

Other option is an AMC7135 driver on one string of 2 LEDs. There is a thread on hear somewhere doing it like this.

Also direct drive.

 

[MrNaz]

Other option is an AMC7135 driver on one string of 2 LEDs. There is a thread on hear somewhere doing it like this.

This option appeals to me, however I didn't think AMC7135 based boards could do over 5V. Using the 7135 chips appeals to me as they are an extremely cheap, extremely efficient way to achieve a good selection of currents.

I would ideally like to have the LEDs in 2P2S arrangement, with 1A going through each string. If an AMC7135 based board could handle the 8.4V of the fully charged LiIon pack and output a nice 1050mA then this would be ideal.

Can you confirm if the 7135 can handle 8.4V? Would I need to pot/sink the boards?

 

[rmteo]

Supply voltage range of the AMC7135 is 2.7V ~ 6V with an absolute maximum of 7V.

 

[tx101]

I have been planning such a build myself
Have you read member Download's "Poormans multi-lux setup" ?

Use 7135 based boards with TWO 18650 cells .... apparently it does work

You can find the thread here


Alternatively DX sell a 5 mode board that will drive 5 x Cree at 800 mA
SKU 26106. Maybe that will work with 4 x R2s ?

I cant decide which method to use for my own build :thinking:


EDIT If you decide to use the 7135 method, DX/KD do sell 8 x 7135 boards
or you could build your own (with multi modes ). Have at StefanFS's "how to"
here

 

[mash.m]

I have been planning such a build myself
Have you read member Download's "Poormans multi-lux setup" ?

Use 7135 based boards with TWO 18650 cells .... apparently it does work

You can find the thread here


Alternatively DX sell a 5 mode board that will drive 5 x Cree at 800 mA
SKU 26106. Maybe that will work with 4 x R2s ?

I cant decide which method to use for my own build :thinking:


EDIT If you decide to use the 7135 method, DX/KD do sell 8 x 7135 boards
or you could build your own (with multi modes ). Have at StefanFS's "how to"
here

the dx driver is also capable to drive 4 in series, cause it is current regulatet. with a small mod on this driver you can drive the r2´s with 1000mA or more. you only have to change the feetback resistor. i have done some mods with this driver, also my bridgelux mod - all with very good results.

markus

 

[rantanplan]

A Maxflex4 from TaskLED would do the job too.

I´m using one in a Mag2C with 4 R2 (in series) powered by 2 18650 batteries. It works fine, if you add a heatsink to the driver (connect it to the Mag body in this case). This setup can provide 1000 mA LED current but it´s on the edge because the input current is above 2 amps even with fully charged batteries. Properly cooled and powered by a battery pack thats stronger than two 18650, it should work pretty fine.

Of course the Maxflex4 is a bit more expensive ($30) and it uses a seperate switch for control unlike usual drivers with an "inline switch". But on the other hand, you get a highly sophisticated and effient driver with tons of options ...