2 sets of 6 k2 leds. run all in series, series / parallel

[Axkiker]

Hey all give me some insight.

I will be running 12 k2 leds in 2 seperate housings. So 6 in each. I plan on using the cchipo driver from task led to run all of the leds.

What do you all think is best for my application. to run them all in series or possible a series parallel combination.

Here are the specifics to the driver if you are not familiar.

CCHIPO - Constant Current High Power driver
V1.2 now available and shipping (1 May 2008)

• Boost converter (4V - 30V input). Maximum 5A input current.
• Fully current regulated.
• Adjustable current limit via onboard precision 25 turn trimpot.
• Connections for optional external Potentiometer.
• Output voltage up to 48V.
• Maximum power output 45W.
• Open circuit protection (maximum 48V output).
• >85% efficiency.
• Board is 2.5" x 1.9". Maximum height at heatsink is 1.65".

V1.2 supercedes V1.1 and has 2 major operational changes as listed below
1) Maximum output voltage raised to 48V (previously 39V).

 

[HarryN]

Hi, both options will work of course as long as the battery pack voltage is less than the LED string Vf.

I would be tempted to run them in series parallel similar to your enclosures. My reasoning is:
- In case one enclosure of LEDs needs to go off line, you can just continue to run the other.
- 12 K2 LEDs in series are getting very close to the 48 V max if pushed toward the upper end of the drive current.

I have looked at using that driver - it definitely is a work horse, maybe a whole team.

Assuming a max drive of the K2s ( 12 ea x 4 volts Vf x 1.5 amps = 72 watts + 20 % for efficiency and Murphy's law = 86 watts

86 watts / 5 amps max input = 17.2 volts minimum battery pack voltage - under load. The driver needs its own heat sinking as well since it might be dissipating as much as 5- 10 watts.

Sounds like a fun project.

 

[Axkiker]

Hi, both options will work of course as long as the battery pack voltage is less than the LED string Vf.

I would be tempted to run them in series parallel similar to your enclosures. My reasoning is:
- In case one enclosure of LEDs needs to go off line, you can just continue to run the other.
- 12 K2 LEDs in series are getting very close to the 48 V max if pushed toward the upper end of the drive current.

I have looked at using that driver - it definitely is a work horse, maybe a whole team.

Assuming a max drive of the K2s ( 12 ea x 4 volts Vf x 1.5 amps = 72 watts + 20 % for efficiency and Murphy's law = 86 watts

86 watts / 5 amps max input = 17.2 volts minimum battery pack voltage - under load. The driver needs its own heat sinking as well since it might be dissipating as much as 5- 10 watts.

Sounds like a fun project.

Well I should have thrown in that I plan on running them at 1A not 1.5A Since ill be working with a 12v battery.

 

[HarryN]

Well I should have thrown in that I plan on running them at 1A not 1.5A Since ill be working with a 12v battery.

Ok, no problem then - re running the math (conservatively assuming 4 Volts Vf for the K2s)

( 12 ea x 4 volts Vf x 1.0 amps ) = 48 watts which sort of includes driver loss and Murphy's law.

48 watts /12 volts = 4 amps , so well within the 5 amp input max.

The perfectionist would drive them all in series to make sure every one of them gets exactly the same current. I am not a perfectionist, and that many LEDs in either 6S2P or 12S will work just fine, as the Vf of the string will average out under load.

The main advantage of running the 6S2P setup is that there is less chance of a wire failure causing the driver output to go "open circuit" and blowing the driver.

Maybe someone else has some comments - Axkiker is probably getting tired of my answers.

This would be a good thread to copy / paste into the K2 info thread - maybe ?

 

[Axkiker]

Ok, no problem then - re running the math (conservatively assuming 4 Volts Vf for the K2s)

( 12 ea x 4 volts Vf x 1.0 amps ) = 48 watts which sort of includes driver loss and Murphy's law.

48 watts /12 volts = 4 amps , so well within the 5 amp input max.

The perfectionist would drive them all in series to make sure every one of them gets exactly the same current. I am not a perfectionist, and that many LEDs in either 6S2P or 12S will work just fine, as the Vf of the string will average out under load.

The main advantage of running the 6S2P setup is that there is less chance of a wire failure causing the driver output to go "open circuit" and blowing the driver.

Maybe someone else has some comments - Axkiker is probably getting tired of my answers.

This would be a good thread to copy / paste into the K2 info thread - maybe ?

NO NO NO I am by no means getting tired of your answers. I need all the input I can get. This stuff is so complex once you break down the many different ways you can do things.That I want as many views as I can get.

Plus its been a LONG time since I had any electrical theory classes. My calculations arent always correct so its good to get reassurance.

 

[Axkiker]

Ok, no problem then - re running the math (conservatively assuming 4 Volts Vf for the K2s)

( 12 ea x 4 volts Vf x 1.0 amps ) = 48 watts which sort of includes driver loss and Murphy's law.

48 watts /12 volts = 4 amps , so well within the 5 amp input max.

The perfectionist would drive them all in series to make sure every one of them gets exactly the same current. I am not a perfectionist, and that many LEDs in either 6S2P or 12S will work just fine, as the Vf of the string will average out under load.

The main advantage of running the 6S2P setup is that there is less chance of a wire failure causing the driver output to go "open circuit" and blowing the driver.

Maybe someone else has some comments - Axkiker is probably getting tired of my answers.

This would be a good thread to copy / paste into the K2 info thread - maybe ?

Let me ask you another question.

If I were to take these 12 leds and break them into 2 sets of 6. Wire each set of 6 in series then take those 2 sets and wire them in parallel would that take the input needed from the driver down to 2 amps insted of 4

Or am I crazy

Im just trying to get the least amout of drain from the battery.

 

[HarryN]

What matters are watts in and watts out. :wave:

Each LED will take about 3.5 - 4 watts to run. 12 of them take 12 each x 4 watts = 48 watts no matter how you string them.

48 watts out needs at least 48 watts into the driver.

48 watts / 12 volts = 4amps in.

The only way to reduce "amps in" is to increase the battery pack voltage.

 

[Axkiker]

What matters are watts in and watts out. :wave:

Each LED will take about 3.5 - 4 watts to run. 12 of them take 12 each x 4 watts = 48 watts no matter how you string them.

48 watts out needs at least 48 watts into the driver.

48 watts / 12 volts = 4amps in.

The only way to reduce "amps in" is to increase the battery pack voltage.

gotcha....... im definatly new to this whole driver deal


thanks