7-up 14,4V whit buck driver

[dolp]

Hi first post on this forum.

I had problem to drive cree 7-up whit my 14,4V battery but now i found efficient buck drivers. PCB LedSenser boost driver is coming and I will try it too.

I cut led board to 4 and 3 series whit two drivers dx sku.26110.

Here is measurements:

4 serial batt 14,99V 1,13A 16,94W leds 12,37V 1,26A 15,59W 92% eff

3 serial batt 15,01V 0,86A 12,91W leds 9,13V 1,26A 11,50W 89% eff

So there is 29,85W battery power and 27,09W led power total 91% eff

30W and 2900 lumens are not bad?

 

[nein166]

Does it flicker? Or do some of the LEDs look dimmer than the others?
A buck driver needs a higher battery voltage than LED Vf, and your running two separate and unequal loads in parallel.
One of the series strings is the weakest link and either the 3up will pull the 4up down in current or the 4up will burn the 3up with too much current.
If your experiencing problems remove one of the 4up LEDs to balance your parallel loads.

Woah sorry I just noticed the driver your using thats your problem buy a maxflex from taskled thats the solution. then rewire it to a true 7-series

Or did I miss the question:thinking:

 

[dolp]

Well there was not question, just one poor man setup for 7-up

First I drive 4 led series whit amc 1050 poor man setup but it did not work well. Thats because 3 led drops 15V voltage to 5,9V and its too much for amc. That was the problem. There is poor man setup.
http://www.candlepowerforums.com/vb/showthread.php?t=201392

This setup whit 4 leds is enough 12,37V makes 3,09V/led and burn well. I dont understand why one led drops voltage only 3,09 when there is 1,26A?

It works well, 3xp7 is quite same lever but 4x mce have more light.

What is the efficiency whit maxflex 15V to 7-up series?

 

[Eltehs]

A buck driver needs a higher battery voltage than LED Vf, and your running two separate and unequal loads in parallel.
[...]
Or did I miss the question:thinking:

Dolp is running this strings from two independent drivers, so no balancing problem with his setup - he really achieve 91% efficiency from 14.4V source.

I see only one potential drawback with this setup - powering 4-LED string from 4S Li-Ion with this driver would not allow to use full batteries capacity with some batteries.
AX2002 driver IC http://www.axelite.com.tw//Products/AX2002-V1.2-20080729.pdf used in this board, would require that minimum input voltage should be ~0.7V higher than LED voltage, or the current goes down significantly. So, for 4S setup you will be limited with minimum 13V input voltage. It would allow you use something like 50-98% of the battery capacity, depending of the cells used. Check this thread for 18650 cells comparison:
http://www.candlepowerforums.com/vb/showthread.php?t=257543