Most efficient way to run LED

[KrisP]

Hi,

I have a 1C Maglite light with a DX 5-mode driver with linear regs on it. This is not the best driver and once the voltage gets down to 3.8V (about 2Ah of the 3.3Ah battery is used) it starts to drop the output voltage, therefore dropping the current.

What i'm looking for is the most efficient driver for a single li-ion to run an LED at 3.5v @ 1A but with multi-modes. The Flupic seems quite good but i'm unsure what the maximum current will be and at $35+post it's quite expensive compared to the $3 DX driver. Even with the Flupic, once the voltage drops below 3.5v or so, the LED is going to stop drawing 1A. Is the Flupic the most efficient multi-mode driver for this application? Or is there a boost/buck driver that has multi-modes? I couldn't find one in the Driver board list / regulator board list. thread.


Thanks

 

[TorchBoy]

Hi,

I have a 1C Maglite light with a DX 5-mode driver with linear regs on it. This is not the best driver and once the voltage gets down to 3.8V (about 2Ah of the 3.3Ah battery is used) it starts to drop the output voltage, therefore dropping the current.

What i'm looking for is the most efficient driver for a single li-ion to run an LED at 3.5v @ 1A but with multi-modes.

My first thought is that if the AMC7135 board is starting to drop out at 3.8V it strikes me that your LED isn't operating at 3.5V, but at almost 3.7V instead. Is it one of those high Vf Cree Q5s? Instead of paying $30 for a driver it might pay to get a lower Vf LED.

My second thought is that maybe the battery isn't 3.3Ah. How did you get that figure?

 

[KrisP]

The LED is a PhotonFanatic SV0 Seoul P4, it has a low Vf which i've measured, but all my data is at work. The battery is a AW C-cell.

From my experience, the AMC7135 boards drop more than 0.1v.

 

[Greg G]

If you don't absolutely need multi-modes a GD1000 from the Sandwich Shoppe is perfect. It was designed to be used with single cell lithium ion batteries.

 

[KrisP]

Yeah, I looked at that but I do want multi-modes. 1A is too bright indoors and I like a lower mode to extend runtime.

 

[TorchBoy]

The LED is a PhotonFanatic SV0 Seoul P4, it has a low Vf which i've measured, but all my data is at work. The battery is a AW C-cell.

From my experience, the AMC7135 boards drop more than 0.1v.

Yes, they normally have to drop more than 0.1 V (that being the way that linear regulators work) but when they drop out of regulation they should only be dropping 0.12 V. So either your LED's Vf is close to 3.7 V at the current you're running it at, or something's not working as it should, such as your battery is prematurely discharging, or there's a really big voltage drop (~1.1 V) across the multimode control chip which is causing the AMC7135s to drop out of regulation, etc.

 

[KrisP]

I know how a linear reg works, thanks. The LED and battery are fine.

Does know of a replacement driver? Or is the Flupic the only option?

 

[VidPro]

there is the Gd-500 also, Formerly known as a WIZZ (or something).

sorry there isnt many drivers that work "perfect" for the single li-ion single led now :-( it needs a "buck & boost" driver , or DC-DC type of curcuit.

the thing you have is a good choice , for the BATTERY the battery will enjoy not being harshed on when low, and the light will run for a long time dwindling like that. (me like, almost direct drives).

all of the "boost" only drivers will "work" but in severe overdrive untill the battery voltage droops down, which will ruin the led and or driver over time.

http://theledguy.chainreactionweb.com/product_info.php?cPath=48_49_61&products_id=961
(the GD)

http://www.candlepowerforums.com/vb/showthread.php?t=188227
(torch boys driver list)

http://www.candlepowerforums.com/vb/showpost.php?p=2216529&postcount=5
(cute pics )

 

[TorchBoy]

sorry there isnt many drivers that work "perfect" for the single li-ion single led now :-(

Once again, if you're fussy about picking a suitable LED, you can find quite a good combination with a range of buck and linear regulators.