This Does Not Compute

Technology, gaming, music and things that just don't compute

Emergency Cell Phone Battery Recharger

We had some severe storms roll through the metro area a couple of weeks ago, and something like 500,000 people lost power. The storm came on a Friday evening, and due to a number of downed trees we had no power in our area until Saturday night. Our iPhones had enough charge to last through Friday night, but by Saturday morning they were almost dead. Sure, we could have just driven around town with the phones plugged into the car until they were juiced back up, but that’s a waste and there weren’t many places we could have gone that still had power. So, with a trip to one place that still had power — the hardware store — I was able to rig up a beefy phone recharger that we could use at home.

A few years ago I had seen at Target a little device that you could insert a pair of AA batteries into and sported a USB port for charging phones and iPods. I thought it was a neat idea but never bought one as I didn’t think we’d ever need it — every time the power had gone out at home, it was only for a couple hours. As luck would have it, though, we couldn’t find any of these chargers after the storms hit; stores had stopped carrying them. There are still some for sale on Amazon, but that wouldn’t have helped as we needed one right away.

Eventually my limited electronics engineering experience kicked in and I was able to come up with a solution that only required one tool and $10 in parts from the hardware store. Here’s how I made the rig shown above:

  1. You’ll need a 12-volt car USB charger, like the kind you plug into the lighter socket. A lot of folks have these already — we have 3 for some reason — but if you don’t, a lot of hardware stores carry these too, for $10 or so.
  2. From the hardware store, you’ll need two 6-volt lantern batteries, some light-gauge wire (18-gauge or so is fine), and some electrical tape. All of this should be about $10. A pair of alligator clips is nice but not required (about $2 for a 6-pack).
  3. The only tool you’ll need is a wire stripper, which you’ll likely already have if you do any electrical work on your house (replacing light fixtures, etc.). Otherwise, these are maybe $5 from the store, and you should own one anyway.
  4. One 6-volt battery won’t charge the phone on its own — the car charger needs 12 volts to work correctly — but two 6-volt batteries wired in series produces 12 volts (hence the reason for buying two batteries). Cut a short piece of wire, strip off 1″ of insulation from each end, and hook the positive terminal of one battery to the negative of the other. This is the yellow wire in the photo above.
  5. Cut two longer pieces of wire and strip the insulation from each end. Notice that on your car charger, there’s a terminal on the side, and one on the very end. The side terminal is negative, and the end terminal is positive. Securely tape the wires to these terminals, then clip the other ends to the empty terminals on your battery.
  6. If your charger has an indicator light, bask in its glory.

I can’t say exactly how long the charger will work for off of this setup. Lantern batteries hold a decent amount of juice, and we were able to charge both of our iPhone 4S’s from empty to full, but I suspect you could get many more charges than that. I tested this rig with an old iPod first (the Nano shown in the photo above) to make sure nothing blew up before connecting my phone.


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