Hardware Reference
In-Depth Information
If you need more receptacles than your car has available, there are a few ways to hack
around that. You can get a socket splitter, which will expand a single socket out to two.
Some socket splitters even add a USB port in addition to the two sockets. With that
setup, you could run everything that this hack needs off one 12 V receptacle. Other
ways to get the power to your devices involve more complicated hardware setups or
custom electrical wiring, so we're not going to cover them here.
Your Car Is a Special Snowflake
Keep in mind that some cars might have these receptacles wired up differently. For
example, on the Dodge Caravan, some of the 12 V ports are wired to the ignition
and provide power only when the car is turned on. Other ports provide power di-
rectly from the battery and will have juice even when the engine isn't running. Every
make, model, year, and variant of vehicle will have its own eccentricities in this
regard, so you should consult your owner's manual to understand the ground rules.
Assuming you don't have a USB power port available (either via a splitter or included
in your car), you'll need to get a 12 V-to-USB converter. These are a lot more commonly
available (and a lot less expensive) than they used to be, but the fact is that you get
what you pay for with these converters. A good rule of thumb is that if they're free,
they're junk.
Let us elaborate on that a little bit before you go off to rage-trash your free converters
that you picked up as swag at your last tech conference. Most of these converters
assume that you are plugging in a phone or a tablet into them. In fact, they even as-
sume you're plugging in an Apple phone or tablet. Apple devices charge over USB at
1 amp of current, so these cheap/free converters often don't offer up more than 1 amp
of current, nor do they try very hard to make that current very clean or regular.
This results in a slow charge for most other devices. Although other devices (such as
your Android phone or tablet) will take 1 amp, they generally prefer 2.1 amps of current
or even more, depending on the device, and as a result, can charge faster. These cheap
converters also have a nasty tendency to be assembled poorly, resulting in a quick
converter death if it overheats (or just has pieces fall off).
As a result, we recommend that you connect your Raspberry Pi to a high-quality con-
verter that provides 2.1 amps of current. We've seen good results from the Media-
bridge High Output Dual USB Car Charger on the 2.1AMP port, but anything with a
dedicated 2.1AMP port (and a total rating of at least 3.1 amps) should do the trick.
We do not recommend that you use a 12 V converter cable designed for charging a
phone (especially not a third-party provided cable), because they often have the same
problems as the cheap converters do. Acceptably poor for a phone, but no good for
an “always-on” Raspberry Pi. As always, your mileage may vary (YMMV), so don't rush
 
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