8523 Views 2 Replies Latest reply: Apr 23, 2012 10:55 AM by M.Emara
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# how many watts to a battery

Hello all!!

I want to make battery operated christmas lights but im not too sure how many batteries to use?

do i have to do some calculations to figure this out. Thanks for looking

• 8 posts since
Mar 27, 2012
Currently Being Moderated
Mar 30, 2012 12:07 AM (in response to micheya)
how many watts to a battery

no point in starting a new thread.... look at my question on the first thread you started...

• 32 posts since
Sep 14, 2011
Currently Being Moderated
Apr 23, 2012 10:55 AM (in response to micheya)
how many watts to a battery

Show more deatils please!! what is the power of lights you want to operate? Sure you must do calculations to know, how much energy you need to operate your lighting system, maximum volt and current. These lights are blinking or just stable lights?

First of all this website is pretty helpful, take a look on electronics components:

http://www.kpsec.freeuk.com/

I will try to make the idea clearer for you. Let’s make a stable lighting system consisting of 1 LED (5mm).

http://www.kpsec.freeuk.com/components/led.htm

Components:

(5mm) Red LED -----> #1

Signal Diode (normal Diode) -----> #1

Resistor

Switch on- off

9V Battery

Before deciding the size of the needed battery for operating your system, you must know the forward current (IF) and forward voltage (VF) of the used LEDs in system. If you can’t take LED specs from supplier, you can use this table as a guide. The table below shows typical technical data for some 5mm diameter round LEDs.

 Type Color IFmax. VFtyp. VFmax. VRmax. Luminousintensity Viewingangle Wavelength Standard Red 30mA 1.7V 2.1V 5V 5mcd @ 10mA 60° 660nm Standard Bright red 30mA 2.0V 2.5V 5V 80mcd @ 10mA 60° 625nm Standard Yellow 30mA 2.1V 2.5V 5V 32mcd @ 10mA 60° 590nm Standard Green 25mA 2.2V 2.5V 5V 32mcd @ 10mA 60° 565nm High intensity Blue 30mA 4.5V 5.5V 5V 60mcd @ 20mA 50° 430nm Super bright Red 30mA 1.85V 2.5V 5V 500mcd @ 20mA 60° 660nm Low current Red 30mA 1.7V 2.0V 5V 5mcd @ 2mA 60° 625nm

Red LED (5mm): VF = 2.1(V), IF = 30mA.

Connect battery in series with, on-off switch, signal diode, resistor, LED. Let’s say that we are using 9V battery. Don’t forget that forward voltage of signal diode is 0.7V so volt after diode will be V(battery) – V (diode), 9 -0.7= 8.3V

Value of Resistance = ((V(battery) – V (diode) – VF) / IF) = ((8.3 – 2.1/ 30 X10-3) = 206.67 OHM, to use a standard value of resistance 220OHM (1/2W)

The link below show how to calculate value of limtting resistor:

http://led.linear1.org/1led.wiz

Kind Regards

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