I have got a white/blue LED that draws 100mA, how long would a plain, normal, standard 9V battery be able to supply enough current for the LED to light up brightly?

And btw, what is the voltage drop over a normal led? Is the drop the same for the type of LED I've got hold of here?

Cheers!
Lac.

 

with regards to battery capacity, you did not specify what type of chemistry your 9V battery is, and it matters.

Since you said plain and normal, I assume it is alkaline type.

Expect between 400 and 600 mAh. A good quality panasonic industrial type shows 570 mAh.. low end type probably more like 400.

You should expect at least 4 hours out of your brightly lit LED.

Typical forward drops for normal LED (for which a 100mA device is not normal) I am talking a T1 type or SMT type that runs up to around 20mA.

Green is about 1.9V
Blue (maybe white also - not sure) more like 2.5 - 3.5V
Reds, ambers and similar are less than 1.9V I believe

These are very rough numbers so consult the datasheet to be sure..

 

Here's data based on duracell batteries... their 9V battery is rated at 580mAh.

 

White LED's are infact blue LED's in disquise :shock: They just have a blue-sensitive phospher coating to produce the rest of the spectrum.

__________________
OLLY_K

 

Hi!

If a 9V is approximatly 600mAh, can you tell me what for a AA? and for a AAA ? Also, is the difference big between a alkaline 9V and a carbon 9V ? Thanks in advance,

__________________
JFDuval
jfduval --@-- aqra.ca
http://www.aqra.ca

 

AA's are 2700mAh. AAA's are 1175mAh (assuming Alkaline)

An alternative for your White LED's drive, try 3x1.2V Nicads/NiMh, this gives 3.6V. which is ideal for white leds NiMh's are available upto 2300mAh.

Even more sneaky, use One Nicad with one IC. ie: MAX1678. This gives a fixed 3.3V o/p @45mA (one Cell) or, 3.3V @90mA (2 cells)

Steve

 

Zinc carbon batteries are really useless, have a look at these discharge graphs I plotted many years ago using two AA's and a 200mA bulb http://www.lpilsley.com/viewbatt.htm.

Notice that two Duracell AA's last about 8-9 hours at 200mA.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Hi! Your link doesn't work...

__________________
JFDuval
jfduval --@-- aqra.ca
http://www.aqra.ca

 

If you mean my link, I just tried and it worked fine?.

Try http://www.lpilsley.co.uk/viewbatt.htm and see if that works for you!.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Hi! Now it's ok. I suppose that the Panasonic High Power is a carbon one?

__________________
JFDuval
jfduval --@-- aqra.ca
http://www.aqra.ca

 

Yes, all it said on the casing was 'High Power', but you can instantly tell from the shape of the discharge graph - useless aren't they!.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Yes, they are!

__________________
JFDuval
jfduval --@-- aqra.ca
http://www.aqra.ca

 

Yes, they are!

__________________
JFDuval
jfduval --@-- aqra.ca
http://www.aqra.ca

 

Yeah, It's really useless. No cash to save their.

__________________
JFDuval
jfduval --@-- aqra.ca
http://www.aqra.ca

 

those "high power" batteries sicken me!!, it's these kinds of batteries that are falsely marked.

I wonder how the metal hydride types would match up???

__________________
www.winpicprog.co.uk - Great PIC language tutorials.