Step Up DC-DC Converter - 4 Powering up a 50w led array from batteries

[X3msnake]

Greetings

I bougth a 50W Led that is rated at 30-34 Vdc with a IF of 1500mA

(**broken link removed**)


I would like to use it to do video illumination powered by a battery array.


- Don't know what batteries to use in order to get the most running time out of it
- Also unsure what DC-DC Step Up circuit I should make for it :/


Is it better to pack batteries in parallel with lower voltage like the RC batts that are rated 3.6v 4700mAh and drain them with the DC-DC Stepper or with higher voltage batteries like the square 9v rated at 200mah

Instead of a DC-DC Stepper is it better to stack batteries to run this, like 4 x 9V 200mah series, and use a resistance to limit the current to the led?


If anyone could help me out finding the info would much aprecciate, i'm trying to learn electronics by miself and i find it difficult at times :|

 

[Sceadwian]

The link you posted displays four different 50w LED's can you please provide the exact make/model of the LED your purchased? Regardless of which specific one just for clarity what you're talking about is not a single LED it is an LED array, if you look at it under 10X magnification and decent light.

I'm not sure why you suggested that RC batteries typically use 3.6V and high amp hours as this is most definitely NOT the case. Typical RC setups power the motor directly from the Lithium pack with no step up or step down and try to match the battery pack to the motors optimal running voltage, voltage controllers are typically only for the servo/receiver end of things, never the motor as properly match a pack to the motor will give you far high efficiency than either step up or step down, even the best of switch modes are 80-90% efficient and only under the best conditions, eliminating them wherever you can is important.

If you can post the datasheet or a link to it for the EXACT LED module you're using I will gladly provide some numbers for reference..

 

[tronitech]

Your link goes to multiple items so.......

Why not three 12V SLA batteries in series with an Ah rating dependent on your running time requirements?

 

[X3msnake]

- LED Emitter: 50W

- Output Lumens: 4500-5000 Lumens

- DC Forward Voltage (VF) : 30-34 Vdc

- DC Forward Currect (IF) : 1500 mA

- Color Temp: 5800~6500K (Pure White)

- Beam Angle: 140°

- LifeSpan Time : > 50,000 hours




There are a couple of things to consider - I need to have the Lowest cost, for the best battery time, and the best portablility for the hole pack, since it should be carried on a belt to power the light that should be over the camera.


Do you know of any 12V batteries that are light and conpact enough and have a good mAh rating?

Best Regards
V.

 

[Sceadwian]

Power handling and thermal characteristics of the package?

Without those numbers you're just designing a fireball.

 

[ronv]

I think if it were me I would use 2 18.5 volt LIPO batteries like here:

**broken link removed**

Then a constant current regulator made out of a low drop out regulator.

You will need to bolt the LED to a heatsink and be careful how much current you use even then.

This is not the best solution, but maybe one of the easiest to implement. The LIPO's give you the lower weight, but the charging will be kind of expensive. See if you can find a heatsink the same diameter as the LED array.

Here is a heatsink to get 50 watts. As you can see it's not made for your application so you may only be able to run it at 10 to 12 watts.

**broken link removed**

 

[ronsimpson]

I have a 50 watt torch that you can use to compare.
Battery is BP5-12 12V 5AH. See data sheet attached. To get 50 watts out of the LED it might take 55 to 60 watts into the switching power supply. At that power level you will get 30 minutes from 4 pounds of battery.

You need a heat sink on the LED that will keep the LED at a reasonable temperature. You need to dump 50 watts into the air. If you had a data sheet you can plot temperature verses lift span.

You are getting a part from e-bay, from a unknown supplier, from a unknown manufacturer, with no data sheet, no application notes. Good luck. These parts are probably factory rejects or copies of real parts. Maybe "China Wholeseller" is a big name company. Ask them for a data sheet.

 

[ronsimpson]

I bougth a 50W Led that is rated at 30-34 Vdc with a IF of 1500mA
I would like to use it to do video illumination powered by a battery array.

Is it better to pack batteries in parallel with lower voltage like the RC batts that are rated 3.6v 4700mAh and drain them with the DC-DC Stepper or with higher voltage batteries like the square 9v rated at 200mah

Instead of a DC-DC Stepper is it better to stack batteries to run this, like 4 x 9V 200mah series, and use a resistance to limit the current to the led?|

If you use a linear current regulator like a LM317 you will need batteries with a voltage above 38 volts.
You can use a resistor to set the current. Same problem, you need some voltage across the resistor.
4 * 9V 200mAH used at 1500mA is 8 minutes. With that load your batteries will drop in voltage (maybe 7 to 8 volts).

I would consider a 24V battery and a boost PWM power supply in constant current mode. To get 32V @ 1.5A from a 24V battery the battery will need to provide 2.1 amps. A 24V battery under heavy charge will reach 29V, so it should work with a 30V LED while charging. 12V batteries are common. You can use 6 * 3.6V 4.7AH batteries.

A boost up supply is forgiving compared to a buck supply. If the silicon breaks in a boost supply it will not burn out the LED.