Wouldn’t you like to have a flashlight that does not need batteries that will last a lifetime? Wouldn’t it be great if you didn’t have to shake it every few minutes to keep it lit up? Then what you need is a super capacitor flashlight.
You will need to buy a pen light (you will need the LED driver board inside the pen light). I got mine at Walmart for $3.50. The part number is BRSLEDPEN-BA.
Or get one here (google shopping search):
The pen light is easy to take apart. The gray plastic part with the lens unscrews. Pull off the black ring. Pull the board out of the white plastic tube. The black wire on the board will be connected to a metal contact on the side of the white tube. Cut the wire at that contact.
I bought the plastic boxes from Radio Shack. You will also need 2 on/off switches and 2 RCA jacks. And you will need a 400 farad capacitor which is available from Future Electronics.
SAMWHA ELECTRIC CO. LTD
2.7 V 400 F, 60 °C Electric Double Layer Supercap
Currently $19.98 each.
By the way, I decided to go with a jack for the LEDs so I can change/upgrade LEDS without re-wiring.
My favorites are 2 piranha leds (shown in the first picture) and a 10mm multi-chip.
The piranhas are available here:
I bought the multi-chip from Goldmine Electronics.
Sometimes they have them and sometimes they don’t. They have them now. In the future this link may not work from time to time. This type is available from other distributors but I like this one. Also, I checked this one with a microscope and verified that it is a multi-chip because I could see there were more than 2 little wires going to the chip. Goldmine Electronics says this is a 220000 MCD LED. Could be but I doubt it.
Since this flashlight puts out over 20 milliamps to the LED when fully charged, powering 2 leds or a multi-chip led is a good idea.
Here is the circuit. It’s easy.
The run time with 2 piranha LEDS on low is 6 hours.
The run time with the multi-chip on high is 2 hours.
Your results may vary.
You can squeeze a little more run time out of it by:
1. Charge the capacitor to 2.7 instead of 2.5 like I did.
2. Use a larger resistance for the high / low part of the circuit.
I have also run a laser diode with this circuit.
You will need to charge your flashlight. Here is the instructable for the DC to DC converter circuit for charging super capacitors:
It's 93% efficient. It could be useful to power up / charge other things.
Or you can make a linear regulator circuit:
I prefer the DC to DC converter. It does not get hot and it is more efficient.
Here is another flashlight. It has two of the 400 farad capacitors. Also there are 2 inputs for charging the capacitors and a switch to switch over from one capacitor to the other. So when you are using the flashlight and it starts to get a little dim you can switch over to the other one. It’s like having a spare gas tank.
Big Ray is shown with the multi-chip LED. The connection for the led is an RCA jack so LEDS are interchangeable.
So there you have it. The capacitor is rated for 500,000 charge / recharge cycles. LEDs typically are rated for at least 50,000 hours if used within normal operating parameters.
You know what that means. Years of fun and no batteries.
If you are interested in an easier flashlight project for long run time emergency lighting try this one:
It’s an easy 10 minute modification.