Step 3: Power supply

Picture of Power supply
To make the power supplies I just soldered some wire onto the ends of the batteries I had bought so that I could easily attach the LEDs to them. The 9V battery served as my 9V power supply, one AA battery made a 1.5V power supply and three AA batteries bundled together made a 4.5V (1.5V + 1.5V + 1.5V = 4.5V) power supply. I didn't use alligator clips on the ends of the wire, but they would have been helpful here.
EfrainM13 days ago

that is very truth...NEVER SOLDER INTO A BATTERY!!! EVER!

Ben Finio2 years ago
Just to reiterate a few older comments below (since this is one of the most popular Instructables on the site) - soldering to batteries is a safety risk and they can explode. Don't do it. Battery holders are cheap and easy to find:


as are clips that fit onto 9V batteries.


For the novice: a "battery holder" is just a plastic box with metal springs inside that push up against the battery terminals, and wires sticking out of the box that you can connect to your electronics project. It's safe to solder to the wires. You can get them in many different sizes (e.g. 2xAA, 4xAA, 8xAA, same for AAA, they make coin cell battery holders...you get the idea) and some have built-in on/off switches which are convenient. The number of batteries you need will depend on your project, but in general battery holders connect the batteries in series, so the voltages of the individual batteries add up. A typical AA or AAA battery you get at a store is 1.5V - so two of them will give you 3V, four will give you 6V, etc.
keys882 years ago
people please try not to solder anything to a battery. if the get to hot they can explode.some batteries easier than others.it's easy enough to just buy or pull out of something else a battery clip/holder.
Could you use button batteries? I want to use the LED's on clothing and those big batteries are to bulky.
macman8085 years ago
for te 9v battery you can just use a 9v battery clip which connects to the two terminals and has 2 wires coming off it. ;^)
nax5 years ago
What about using one of those wall plug things that come with so many electric things? They usually have the voltage and amps stamped on them someplace.
s600cam8 years ago
Never solder anything to a battery. Instead, use a battery pack and place the batteries into that. Soldering to a battery can/will make it explode, and battery acid will get everywhere.
 Most batteries these days have a more powdery substance in them. Although I still would not recommend it.
Lookup the MSDS for Energizer alkaline batteries which recommends not soldering anything to the battery because the solder can cover the vent holes which keep them from exploding in the event of extreme heat or general failure. Ever leave a battery in a device for a long time and come back to find it corroded, yet no evidence that the battery exploded? That's because the catalyst can ooze through the vent holes rather than building up pressure.  "Batteries normally evolve hydrogen which, when combined with oxygen from the air, can produce a combustible or explosive mixture unless vented. If such a mixture is present, short circuits, high temperature, or static sparks can cause an ignition."    http://www.officedepot.com/pdf/msds/696526.pdf
what does a battery pack look like? any links? thanks : D
batman20005 years ago
I fly electric model airplanes and have soldered up many battery packs.  The secret is to tin the battery terminal first then solder the wire to it.  You should use at the very least a 30 watt iron to get the heat to the terminal as quick as possible so that you don't heat the battery too much.  It is important not to get the battery hot as this may ruin the battery and could even lead to thermal runaway and possibly an explosion.
Rileymi3235 years ago
or solder the wire to a piece of aluminum and then tape tht to the ends of the batteries??
Good idea Riley, thanks for turning me on to this site, your phlebotomist, Bill
Cynda26 years ago
where do you get the wire?
arvinx56 years ago
so you mean the black is the positive and the red is the negative
You can also try an AC to DC power supply such as a wall mount transformer or house plug. Be sure to use a voltage regulated power supply or the voltage will be higher than required if your circuit does not draw the specified current. This page has lots more info on basic LED circuits: http://www.lunaraccents.com/nav-educational-LED-information.html
uh, i dont really know a lot at all about this stuff...can you just use electrical tape and tape the wires to batteries?
noahw (author)  Unforgiven_God8 years ago
If your going to use the battery just temporarily to play around with electrical tape will work fine. If your building something thats going to be more a permanent installation I would recommend getting a battery holder. You can then solder your wires onto the holder directly and change the battery as necessary.