There's an outdoor area I'm working on, and I want to build a small station where people can charge their phones. There's no access to house power in the area. I've looked into solar chargers, but they seem impractical, so I was thinking something like a car battery or other large battery might work.

Is that the best way to do this? I need something that can be removed and charged, and then hooked up to a USB port. Thanks for any help!

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    \$\begingroup\$ A car battery and a DC-DC converter tuned to 5v would basically work, and probably more efficiently than automotive charge adapters. Just don't short out or mishandle that big lead acid battery! If you want to charge at greater than USB rates you will have to work out the semi-compatible details of signaling that capability to various model phones. \$\endgroup\$ – Chris Stratton Dec 1 '15 at 0:43
  • \$\begingroup\$ Hmm. A solar charger seems impractical to you, but lugging a battery back and forth seems practical to you. Good luck with that. You'll find that a solar charger looks a lot more practical after a few months, I suspect. At least you'll have a battery for the solar panel and charge controller to work with, if you haven't killed it by not bothering to charge it for too long... \$\endgroup\$ – Ecnerwal Dec 1 '15 at 0:50

Anyway the simple approach is to grab a few car power point (lighter socket to us old folks) USB chargers and use a 12V battery. Put a fuse on the thing before anything else. That will be the simple way to get full-bore charging (but you might need to segregate apples and androids since they do it differently, and possibly also some different brands of androids) - else any 12V-5V converter will do the job at the low-power range.

Some of those probably do use a DC-DC converter, some may not - if you could identify which do, they are likely to be more efficient than those that don't.

You'll also need a low-voltage cutout to shut the system down when the battery is drained.


simulate this circuit – Schematic created using CircuitLab

  • \$\begingroup\$ Thanks so much! So assuming I get a 12V 8 Ah battery, I'd need to add a fuse, then a 12V-5V converter, then the lighter socket chargers? \$\endgroup\$ – deanboysupreme Dec 1 '15 at 1:47
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    \$\begingroup\$ @deanboysupreme - the light-socket chargers already have 12V-to-5V converters in them. They're designed to connect directly to 12V. You want 12V battery + to fuse to lighter socket central pins and lighter socket shells to battery -. \$\endgroup\$ – DoxyLover Dec 1 '15 at 1:50

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