James O'Neill's blog

Windows Platform, Virtualization and PowerShell with a little Photography for good measure.

USB Battery

USB Battery

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**Warning** Neither I nor Microsoft will take any responsibility for what happens if you follow these instructions.
I am not recommending this, just reporting my experience.

For ages now I've had a bookmark for a hack to make a "USB Battery". I wrote ages ago about making up cables to power things from USB... but and I have both mains to USB and  car cigar lighter to USB power Adapters. But what if I'm stuck miles from either. I prefer devices rely on AA batteries and SD cards to minimize the risk of being stranded. But what about my USB dependant things, like my phone. Wouldn't it be good to be able to plug in a standard PP3 battery.

I thought I would do something equivalent so went to my local Maplin and bought the following (stock codes in brackets)

  • PP3 Clip (HF28F)
  • 5V Voltage regulator "7805 Value Brand" (CH35Q)
  • USB 2.0 Type A Line Socket (N99FK)

I stripped some of the insulation off the negative lead from the clip to solder it to the ground pin on the regulator. I clipped the positive lead off and soldered the two parts to the in and out pins on the regulator, and then the free ends go onto the USB connector: A check of the voltage showed I'd soldered them back-to-front initially (see the pictures below), so having fixed that and clipped off the USB data pins from the socket I just needed a wrap round with insulating tape to protect everything. I Plugged my smartphone in and hey presto I can charge it.  One more home made gizmo for the travel pack.

Left to right - first attempt to connect the socket, Second attempt, with the pins clipped off. I wrapped it once with tape, and then folded the leads back on themselves and wrapped round again. The regulator is taped to the PP3 clip, and you can see how the leads are connected to it. These also got wrapped in tape. In Final frame, the adapter is finished and charging the phone ...

usb-battery

**Repeat** Neither I nor Microsoft will take any responsibility for what happens if you follow these instructions.

Comments
  • you need soldering lessons

  • :-) I did a lot of soldering 20 years ago, and I do seem to have lost the knack of doing it neatly. Of course something to hold the bits while I'm working on them would help too !

  • Swapping the 9V battery for 4 x AA (6V) would give you less voltage drop across the 7805 and so less wasted energy. Maybe get HF29G (Maplin) to hold them, think it also has a PP3-style clip. In fact, I reckon 6V is close enough to 5V that you could probably get away with no voltage regulator at all... but you can test that on your phone first!

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