$9 Emergency Phone Charger 10 Minutes

Power off? Grid down? Hurricane? Tornado? Camping? Apocalypse? Cross eyed lumber jack down the street?

I want to show you how to make a quick, simple and cheap DIY phone charger with basic tools and skills - anyone can do this. Shelf stable, clean - with no lead acid battery mess!

I used $9 in parts sourced at Harbor Freight and it took me less than 10 minutes.

Check out my guide to coupons and savings at Harbor Freight!

Please read about enhancing the quality of life for persons needing affordable prosthetics at the end of this instructible.

Supplies I used:
12V dual outlet adapter - $4.99 on sale at Harbor Freight
(2) 6V lantern batteries - $2.49 on sale at Harbor Freight
Automotive fuse - on hand (recommended not necessary to work)
(2) Standard female terminal crimp ends - on hand (recommended not necessary to work)

Don't forget to take your 20% off and a free item coupons!

Tools:
Cutting Pliers - but a cheap knife or scissors could be used in a pinch.

Not pictured:
Your phone's car adapter

*Note - I used the dual adapter because it was cheaper and I'll have an extra 12v outlet for a later project. This extension or this extension will do just fine too!

We need to separate the wires out of the adapter - but we need to know which is positive and which is negative. This is easily done with out any additional tool if we just take it apart.

Unscrew the cap on the 12V adapter.
Remove the fuse.
Pry open case and separate it from the wires.

Before cutting note which wire attaches to the center pin where the fuse was attached. This is our positive lead. Cut one positive wire off and mark it somehow. I tied a knot in mine.

Cut ground wire off at the soldered prong.

Put the two batteries in series. This is a fancy term for linking the batteries together in such a way that we double the voltage.

Put the two batteries together side by side. I put electrical tape on mine to keep them from moving - helpful but not necessary.

Measure a piece of the negative (ground) wire (the one not marked or without a knot) about an inch or two longer than the distance between one positive terminal and one negative terminal. Cut it with your pliers.

Strip away about a quarter inch of the insulation on each end of the wire. On battery 1 tip the spring on the positive terminal to one side and slide one end of the wire under the spring. On battery 2 tip the spring on the negative terminal to one side and slide the other end of the same wire under the spring. Place the terminal caps back on the used terminals.

Pro Tip: Series Vs Parallel
Batteries in Series: Connect (+) to (-) and double your voltage.
Batteries in Parallel: Connect (+) to (+) AND (-) to (-) and double your amperage - or the Amp Hours of your battery bank.

Both series and parallel should be done with matching batteries.

Strip away about a quarter inch of the insulation on the adapter end of the negative wire. On battery 1 tip the spring on the negative terminal to one side and slide the other end of the same wire under the spring. This will be the negative terminal not used in the previous step.

Recommended but not functionally necessary

Add a fuse:
On the positive wire cut about 3 inches or so and strip a quarter inch or so off both ends. Crimp one terminal to one end. On the remaining positive wire still attached to the adapter strip off a quarter inch of the insulation and crimp on the remaining terminal. Put the one terminal on each lead of the fuse. *Note - please use a good fuse. See how the fuse in my photo is blown.* Put a small piece of tape around the crimped terminals to avoid shorts.

On battery 2 tip the spring on the positive terminal to one side and slide the stripped wire under the spring. This will be the positive terminal not used in the previous step.

Put in your adapter and charge up your phone.

These batteries are inexpensive - but they house 4F batteries each. This will give you a total of about 28 amp hours at 12V. Roughly the same as 104 AA batteries.

This little DIY build hack is great for camping, an emergency grid down power outage or for my for my prepper friends to toss in the bug out bag/vehicle. Charge your phone inside in a pinch without spilling a lead acid battery all over the place.