Driving 8 Cree Q5's with 4 AW C cell lithium ions

[Greg G]

I was thinking about separating the LED's into two strings. Would using 2 SOB1000's, one for each string of four LED's (in series) work in this light (3 D M@g)? The max input volatge for the SOB is rated at 16 volts. Fully charged batteries might reach 16.8. Has anyone tried this?

Other reccomendations?

Thanks.

 

[Greg G]

I'm serious about this, so someone better help me.


I can possibly run 7 Cree's off one Shark, and the 8th Cree off an SOB1000. That would be kind of a ******* setup though.

Can a Shark be modded to have a 30 volt output? That would fix everything right there.

I *could* run two Sharks, 4 Cree's per Shark, but I'd only be able to run 3 AW C cells then because the voltage in would be too high with 4 cells. I can fit 4 cells in the light, and want the extra capacity.

Thanks,

Greg

 

[dat2zip]

You could use a linear Regulator instead of a Switcher. If Vin and Vout are close the efficiency is very good.

With 4 LEDs your starting voltage is 2-3V difference. That might not be bad for a linear setup as over time battery voltage would fall and the linear wouldn't have to work as hard. It would have a similar dimming effect when the linear drops out of regulation.

There are some linear and other regulators at DX and Kai. Have you looked at those? I think the buck puck is linear and might run off higher than 16V.

Wayne

 

[Greg G]

I'm not going to buy from KD or DX. Too much of a hassle, and I'm suspicious about the quality. I've bought all of my boards from you and have been satisfied.

I would like something that would give me flat regulation. That's why I asked if the Shark could be modded with higher capacity parts to handle 30 volts.


Greg

 

[dat2zip]

The current voltage output is set to ~28V or so. If the 8 LEDs Vf were 3V that would make the total 24V. If the Vfs were 4V each that would put the total around 32V.

Depending on how hard you drive them and the Vf of the total string 28V should still provide 500+ mA to the LED string. Either it reaches regulation or it hits voltage limit.

A Shark will drive the 8 LEDs. When it hits the voltage limit that will be the max you will get out of that configuration. It may be 950mA or it may be something less. Still, that sucker will be bright me thinks. :twothumbs

I might be able to do a one time custom if the IC has the voltage range. One resistor change could up the voltage limit. Lemme go check...

Wayne

 

[dat2zip]

I can raise the limit to anything less than 40V. Maybe 37V would be a safe number.

Of course, it appears there is a potential issue. When we raised the voltage limit to 28V I've heard of users that have killed the board with no load. So, I would be careful and not use it in that mode and always connect a load to the board when testing or using it.

Wayne

 

[Greg G]

I won't go hot with it until the LED string is wired up to the Shark.

The emitters are new production Cree Q5. I have 20 of them, and will test them all to find the 8 with the lowest Vf. I want to push the full 980ma to them if possible.

Thanks,

Greg

 

[Greg G]

PM sent about doing this.

Thanks,

Greg