Can I direct drive 4 Crees in series from 12V?

[Vermonter73]

Can I direct drive 4 Crees in series from 12V? :thinking:

 

[glockboy]

Some of the Crees I test, it's 3.6 @ 1amp.
At 12V it will not bright at all.
If you want bright, it have to be 14.4V or you can add the Fatman board to your 12V.
http://www.taskled.com/fatman.html

 

[Timson]

If your 12v power supply is a car battery - Assuming the battery is in good condition, you should be actually working with 13.8 - 14v.

That's ballpark forward voltage for 4 series connected Cree's.

A car batteries voltage won't sag at all at 1A current draw - So I recon you ought to get a decent drive current (perhaps not a full amp...but something approaching).


What have you got in mind?


Tim.

 

[rdh226]

If your 12v power supply is a car battery - Assuming the battery is in good condition, you should be actually working with 13.8 - 14v.

Actually...if your 12V power supply is a car electrical system (read: alternator run by engine)...

then you'll be seeing about 13.6-13.8V nominal, with "brief" 14.4-14.6V periods right after starting
as the system recharges the 12V battery.

Even a monster 12V LA battery will only hold "13V" for a few moments before settling down to it's
nominal 12.6V for the long-haul.

That's ballpark forward voltage for 4 series connected Cree's.

A car batteries voltage won't sag at all at 1A current draw - So I recon you ought to get a decent drive current (perhaps not a full amp...but something approaching).


What have you got in mind?


Tim.

 

[Mash]

I have been playing around with crees aand PSUs for a while. Have run 3 crees from 12V and 10V psu, and I couldnt tell that much difference by my eyes.
I have measured currents with different PSUs, now my question is this:
If my measured current is 1A even with the 10V psu (for 3 crees in series), does it mean the LEDs are performing at their maximum? ie can I judge the performance just by measuring the current?

 

[Calina]

I have been playing around with crees aand PSUs for a while. Have run 3 crees from 12V and 10V psu, and I couldnt tell that much difference by my eyes.
I have measured currents with different PSUs, now my question is this:
If my measured current is 1A even with the 10V psu (for 3 crees in series), does it mean the LEDs are performing at their maximum? ie can I judge the performance just by measuring the current?

Short answer: YES !

 

[X_Marine]

Sounds like something I have been tryin to get to for some time now. I want to add led backup bulbs to my ride and was thinking of the possibilities. Only prob if used in series is if one fails the other 2 go as well correct?. and is there a work around short of parallel?.

ThanX for and suggestions.
X..

 

[Calina]

Sounds like something I have been tryin to get to for some time now. I want to add led backup bulbs to my ride and was thinking of the possibilities. Only prob if used in series is if one fails the other 2 go as well correct?. and is there a work around short of parallel?.

ThanX for and suggestions.
X..

You are right: connected in series, if one LED fails, you're out of light.
The best work-around this is to carry some kind of spare (a simple flashlight will do); luckily LED lights are quite sturdy.