Laptop/Chormebook mobile charger

Have you wanted to take your computer with you but forgot to charge it and don’t have a portable charger. This do it yourself blog post will help.

What you need

• A soldering iron
• 2.2k resistor(Optional power led resistor)
• a LED or more(if you want lighted Cigrette lighted sockets)
• A Resistor that is $$\frac{12_{V}-(n*V_{F})}{I_{F}}$$ Where Vf is the LED Voltage Drop, n is the number of LEDs and If is current usually 20mA
• DC-DC boost converter that outputs the same voltage as your charger but runs on 12vdc
• A spear ac adapter to salvage the connector that fits the computer(I used one from a old motorola cellphone charger adaptor that I got from a hamfest)
• Cigrette ligher cable. Got that from the hamfest as well!
• Female Cigrette lighter connector I got two of them with 3 connectors each for free.
• Heatshrink tubes(Prevents short circuits)

My chromebook uses 19VDC @ 2.31A so I looked at eBay for a boost converter, this is because car voltage is only 12VDC it needs to be stepped up. The chromebook may run from 12VDC directly it probably won’t charge. I got a 3 female Cigarette lighter socket from a hamfest and add 3-green LED in series with a 240-ohm resistors and put them close to the hole in the middle of socket, making the sockets lighted.

Steps

1. Cut the cord with the end that fits the computer. DO NOT CUT IT TOO SHORT BECAUSE WE WILL USE THAT PIECE TO ATTACH THE BOOST CONVERTER TO THE COMPUTER.
2. Use your multimeter to find the wire that goes to the tip(Center usually +) and the sleeve(Usually ground). Solder them to the output of boost converter. You may want to attach it to a insulator on copper tape if your going to add a LED.
3. Connect the LED with the anode(before the arrow on the LED symbol) to resistor and +Vout and cathode(the line, after the arrow symbol) to ground This LED lets you know if its on, wired correctly and has enough juice to power the computer(it will flicker/blink if the computer overloads the boost converter
4. If you want to light up the cigarette lighter female plug just put them close to hole where the center +12v is. You can wire them in series for multiple jacks, like in the circuit below. The formula for the resistor is $$R_{1}=\frac{12-(V_{F}*n)}{I_{F}}$$ where Vf is the forward voltage drop n is the number of LEDs and If is forward current.