## Step 2: Assemble and wire

Use the two # 4 screws and nuts to fasten the heatsink and LM317 to the top of the box, with the LM317 leads to pass through to the inside of the box.

Cut the power jack from the notebook power supply. This is usually a round ( barrel) plug which plugs into notebook). Strip and tim the leads.

Usually, the center wire is positive, but use a voltmeter to ensure this is true

Strip and tim the wires which will connect the regulator box to the auto power plug. I used 10 feet of 16 guage lamp cord because it was handly. long is good, as it allows the electronics to be placed out of the weather.

Wire the box per the schematic. Make sure to not have either of the pairs of wires to touch the metal box. The metal box is already connected to one of the pins of the LM317. Repeat, DO NOT WIRE ANYTHING TO THE METAL BOX.

Use generous amounts of hot glue to fasten down the resistor, the wire leads, the leads of the LM317, and the points where the leads pass in and out of the box.

Plug in the notebook power supply, and measure the voltage on the auto power plug. This needs to be 13.7V or more for proper operation. In the below pic, it is 16.16V, a relatively optimal voltage.
since you use the LM317 why don't make the specific ciruit for this job provided in the manufacturer datasheet?
my question is. how much power input does the battery need to be input to charge.<br /> <br /> i used a computer power supply but it did not work<br />
<strong>-12v + +5v&nbsp;&nbsp; make +17v which help u for charge battery</strong><br>
PLEASE do not use this circuit, it will ruin your battery, or worse. Use the circuit from the LM317 datasheet on page 21 titled &quot;12V battery charger&quot; (duh). The input voltage needs to be at least about 17V.
This is stupid. Why did you wire the LM317 as a constant current source? How about reading the freakin data sheet? How about actually using it as a 13,8V regulator, that you could leave hooked up to the battery indefinitely for float charging? If you ran the circuit in the schematic from a standard 19V laptop power supply, the output would be &gt;16V, and the battery would produce LOTS of gas (hydrogen + oxygen). Nice way to blow up your house.
so, a. can this be used to charge a 12 volt electric scooter battery? and b. can i use a 1.2 ohm resistor?
" If the battery is 12V, then OUT pin of the LM317 is 1.2V greater, or 14.2V. " 14.2V? shouldn't it be 13.2? if the input for the LM317 needs to be 1.5V greater than the out (which is 13.2 or 14.2), The computer charger needs to be around 16 - 17 V. Mine puts out 19V. I have an extra 18V cordless drill charger that puts out 19V 2.2A, would this work in place of the comp cord?
Cool.
Do you actually need to regulate the voltage? What would happen if you just connected the notebook charger? L
. If you did that to a discharged battery, things would probably overheat. According to the author, the regulator is actually being used to control current (see Step 4). A schematic would probably go a long ways toward explaining it.
there is a crude schematic in one of the pictures
. Oops. Didn't notice that. And it's hard NOT to see. <sigh>
A very high quality charger would provide a temperature-compensated regulated float voltage of about 13.6V. That however is somewhat difficult, and not necessary considering that 1.2A is really just a trickle. The idea was cheap and simple. Note this charger should not be left on indefinitely, as noted in the instructable.
Do you need the voltage to be regulated, or would the notebook charger work anyway? I'm asking because I don't know. L
If you're not supposed to wire anything to the box, how come your schematic shows a wire connecting negative to "case"? And, the picture shows two wires soldered to the box. This matches your schematic but not your written instructions.
Good catch, I did make the mistake of soldering to the box, and I should know better. I subsequently unsodlered the wires from the box. That was easier than locating an isolating washer for the TO220 tab on the LM317.