Hello,

I am an extreme amature when it comes to electronics - sorry!
I am trying to understand the how long a 9 Volt battery (typical consumer Duracell) will illuminate an LED (generic - low cost - red). Assuming the LED is connected to the battery in the appropriate manner --- with the correct resistors, etc......?

I am trying to get maybe 1 year illumination of the LED with a compact (readily consumer available) battery - any suggestions?

Thanks for any help!

 

QUOTE=e-amature]Hello,

I am an extreme amature when it comes to electronics - sorry!
I am trying to understand the how long a 9 Volt battery (typical consumer Duracell) will illuminate an LED (generic - low cost - red). Assuming the LED is connected to the battery in the appropriate manner --- with the correct resistors, etc......?

I am trying to get maybe 1 year illumination of the LED with a compact (readily consumer available) battery - any suggestions?

Thanks for any help![/quote]

This should get you started:
http://www.powerstream.com/9V-Alkaline-tests.htm

 

one 9V battery will give you somewhere between 120 and 200 hours of illumination with the simplest circuit, a series resistor. With a good switching voltage converter circuit you should be able to get more than 600 hours.

It is possible to get as much as 1 year or more if it is acceptable to flash the LED rather than leaving it on constantly. I've built an LED flasher that should operate for 3 years from a single Lithium AA cell.

__________________
RadioRon

 

Great, I had a reply all typed out in one of this guy's three copies of the same thread, and by murphy's law, I chose one of the two that the moderators deleted while I was typing Oh well...

In short - battery capacities are rated in amp-hours (current * time). Smaller batteries are usually in milliamp-hours (mAh). To find out what battery capacity you need to run something for a given period of time, multiply the current it runs at by the desired time of operation. A year is close to 9000 hours, and LED's are going to need at least a few mA - so you're looking at tens of amp-hours. By the discharge curves linked by Rolf, I'd say that a 9v battery is less than 5% of the capacity you would really need.

Plus, a 9v is a very poor choice for a single LED because you'd be dropping like 7v across the current-limiting resistor, meaning the majority of the power coming from the battery is wasted in the resistor. A pair of D-cell batteries would do much better - only about 3v with two in series (so much less power would be wasted in the resistor) and a quick google search revealed they can have capacities of on the order of 20,000 mAh
http://www.batterystore.com/Eveready/EN95.htm
I've seen crappy cardboard stand-up display/advertisements at fast food places with some LED's in them, and usually they have a pair of D-cells stuck to the back.

__________________
EEgeek.net

 

Thanks for the input - I will head to your linkand try to educate myself - Thanks!!!

 

How long would the interval be for the blinking LED - also, do you have a schematic of this that your willing to share?

 

I will address may packaging size requirements - it appears 2 D-cells may be the answer!!

 

Hi e-amature,

Here's a blinking led circuit, although it uses a high efficiency led.
It was designed to operate from a 9 volt battery and to consume as little
as possible.

on1aag.

Attached Images

LM3909 replacement.GIF (7.1 KB, 26 views)

 

The flash interval is quite long, made to look like a car alarm. Typically about 5 seconds off and maybe 20 mSec ON.

Here's a single cell flasher circuit: http://www.discovercircuits.com/DJ-Circuits/1vled3.htm

__________________
RadioRon

 

The battery must operate for 24 x 365= 8760 hours in one year. Then at an LED current of 20mA the battery capacity must be 8760 x 20ma= 175,200mAh.
Energizer's site lists 20,500mah for their alkaline D cells so you would need 9 in parallel and doubled to get 3V. Have you ever lifted 18 D cells?

A 9V battery has skinny AAAA cells inside that are too small to power an LED for any reasonable length of time.
A red LED needs about only 1.8V so using a 9V battery wastes 7.2V.

Two AA cells (3V) can power a red LED about 5 times longer than a 9V battery, are about the same size and cost much less.

My 3V LED Chaser project uses two AA alkaline cells and its red LEDs blink brightly for about 1 year.

__________________
Uncle $crooge

 

Hmmm, I think I have atleast 18 D cells on my desk..... maybe thats what I should do with um......