Jeremy W. Langston

Personal Website

Battery-powered USB Phone Charger

I was getting ready for a long train ride from KY to DC and found out there aren’t any AC outlets for coach seats!  A 15hr ride isn’t too bad when you have a smart-phone; then again, the stock battery on an HTC Incredible will last only about 3hrs of heavy usage.  Not good.  I wanted a way to be able to use it for, well, 15hrs.  So, using some easy-to-find parts I made an extended battery that will charge the phone via USB.  I also wanted the extended battery to be rechargeable.  So, I need to be able to have access to the battery contacts; maybe later I will add something fancier, but for now the battery disconnects from the USB circuitry.  Here’s my finished product, and how to make it.

IMAG0075

I bought a battery from the local Home Depot for $20 (look in the outdoor lighting aisle).  It is 6V and provides 6.5AH.  You can get it cheaper at places like batterymart.com, but I was in a hurry and the shipping on seal-lead acid batteries is not cheap.  The higher the amp-hours (6.5AH in this case), the longer you will be able to run your USB device.

IMAG0064

Now for the voltage – USB uses 5V DC.  I needed to drop the voltage from 6V to 5V, preferably without too much loss.  There are three main options:  voltage divider using resistors, non-switching regulator, and a switching regulator.  In the case of the voltage divider, the resistors basically turn the extra voltage into heat, and they would need to be rated for higher power than the typical $0.01 resistors.  Switching regulators, or DC-to-DC converters, are much higher efficiency, but are more costly.  Also, I couldn’t find one that would work at Radio Shack, so I went with a non-switching regulator:  the 7805.

IMAG0066

The 7805 regulator will take voltages higher than 5V and hold them at 5V, also allowing up to 1A of current.  While that’s much more than is needed, it gives a nice buffer.  A regulator has three legs:  1) input, 2) ground,  and 3) output, where the ground leg is shared between the input and output.  The input comes from the positive side of the battery, the output goes to the 5V pin on a USB connector, and the negative side of the battery along with the GND pin on a USB connector both connect to the ground.  Since the 7805 drops the difference in voltage by heat, adding a heatsink to the regulator might be needed, depending on how much power your device will draw.

IMAG0063IMAG0068

To connect USB devices, I need an adapter that would allow me to plug in a standard USB cable, like the one in your computer.  I happened to have an old PS2/USB adapter from an old mouse.  It hasn’t been used, ever, so I cut it up (the green thing above).  You could use something else, like a USB extension cable which already has wires to solder to.  USB connectors have 4 pins:  1) 5V, 2) Data+, 3) Data-, and 4) GND.  Use some wire to solder the connections (USB 5V -> 7805 Output), (USB GND  and Battery negative -> 7805 Ground), and (Battery positive -> 7805 Input).  Make sure to protect the solder points with some heatshrink or risk shorting, melting, and other bad things.  To connect the wires to the battery terminals, I used spade connectors.  Also, leave the terminals pointing up for reasons I’ll point out soon.

IMAG0067IMAG0069

Once the soldering is done, connect the battery and use a multimeter to check the output on the USB connector (voltage across pin 1 and pin 4 should be +5VDC).  Then you can freely connect a USB device and you’re set.  You could stop here and be done.  Since I wanted this for travel and didn’t want exposed wires, I took it a step further:  enter hot glue.

Clean the top of the battery and add a layer of lubricant (e.g. WD-40) to keep the glue from sticking to the battery.  We want the circuitry to be detachable so that we can recharge the 6V battery using a trickle charger/car charger.  This is why I left the battery terminals sticking up – so that I can freely pull the circuit away from the battery.  I used about 10 – 15 sticks of hot glue used on a mini gun, just to make sure that everything would hold together.  This is the most time-consuming part.  It doesn’t take a lot of thought to do this.  Just fill in all the holes, keeping the USB port accessible.  You also want to keep the heatsink partially uncovered so that it passing air can pull away the heat given off by the 7805 regulator.  You could spend a lot of time getting this pretty by squaring up the sides and making it colored, but this was a last minute project for me.  Hopefully you will get some good use out of this – I know I will.  I hope they don’t kick me off the train thinking it’s a bomb.

IMAG0070IMAG0072

IMAG0077IMAG0078

IMAG0073

12 Comments

  1. Looking for a getaway from the hustle and bustle of Pune? Then book a Manali tour package from Mahadev Tours And Travels! Manali is a beautiful hill station in Himachal Pradesh that is perfect for a relaxing vacation. With our package, you will get to enjoy all the best that Manali has to offer, from stunning views of the Himalayas to adventure activities like trekking and rafting. So what are you waiting for? Book your package today!
    https://mahadevtoursandtravels.com/manali-tour-package-from-pune/

  2. Finance Assignments involves calculations, collectioin and analysis of data. If you ever prepared any assignment in finance then you know the level of frustration while collecting the data and preparing the assignment. Complex calculation can add to the irritation. finance assignments requires specilization. Now you can avail online finance assignment help at your fingertips. Hire from among the experts in the field, and skyrocket your grades.

  3. Finance assignments are one of the most complex assignments to prepare. It is better to hire a subject expert to do the task for you. Now you can avail online finance assignment help at your fingertips. Hire from among the experts in the field, and skyrocket your grades.

  4. Good post, thanks for your information. Have a nice date with VIP models in Ahmedabad for a more romantic date during your alongside. For more information click here: https://www.preeti-patel.com/

  5. nice website… Call Girl in Noida Independent Call Girl Service in Noida Calling 24/7 Escort Service.

  6. We should use an original USB charger for see a better result. And to keep maintain out mobile device safe. Because using other companies’ USB charger can be occurs the problem to a different devices.

  7. Good post, Thanks for giving useful information.

  8. I was read your blog that give a such an inspirational for me. It has good information which i found everywhere but when I saw you blog, I really like it. So, if you are looking for the best a botox medicine you can contact Medcare Aesthetics.

  9. Are you looking for the hottest and most sophisticated escorts in Lahore? Look no further! We have an amazing selection of luxury call girls in Lahore who are available to make all of your fantasies come true. From the beautiful and exotic to the more discreet and sophisticated, our escort services in Lahore have something for everyone. Read on to learn more about the amazing selection of call girls in Lahore that are sure to make your experience unforgettable!

  10. DO MY ASSIGNMENTS
    If you are looking for an online academic writing company to ask them to ‘do my assignment,’ Archlite Assignment service is the right place. We are providing high-quality services at the lowest prices to help students ace their results and complete their degrees with flying colors.
    Many students struggle with their assignments and are looking for expert help with assignments. You must be wondering: can someone “write my assignment for me”? Well, now you need not struggle anymore as you’ve stumbled upon Archlite Assignments. With a professional team of highly experienced writers, researchers, proofreaders, and editors, we have assisted several students so far in submitting top-notch academic papers.               
    From assignments, essays, case studies, theses, dissertations, and PowerPoint presentations, we have subject-oriented experts to work on every given project, irrespective of its complexity. Be it any subject or topic, we can write your assignment with the utmost precision and perfection. Having us by your side, you need to stop fretting over the originality, format, grammar, and timely submission of the paperwork. Just say- ‘do my assignment’ and our professionals will respond quickly with the best quality write-up.

Leave a Reply to end of lease cleaning sydney Cancel reply

Your email address will not be published.

© 2022 Jeremy W. Langston

Theme by Anders NorenUp ↑