It's nice day for a ride to the beach. You grab your stuff jump and in the car. Ooops - last night you forgot to charge your phone and you've only got about 30% but...... No worries, the beach is a 90 minute drive away which should be more than enough time for your phone to charge.
Fast forward - phone GPS running and some tunes along the way. Park the car, grab your phone and...... #$%@* only 25% charged?? It was plugged in for the entire drive?! You checked it when you plugged it in and the phone was properly connected.
You've been Auto USB'd!
What Happened?
If your car has a USB port built in - that port is most likely low power, only delivering around .5 Amps. This is considerably less than your phone charging capacity and because you were using the phone GPS, playing some tunes, etc...... well, you get the idea. And if you were using one of those cheapo cigarette lighter adaptor chargers, it is also probably only delivering only around .5 Amps of charging current. The cheap plug ins can get even worse - if you've got one of them with two USB ports and have a couple of phones plugged in, that .5 Amps total gets split to .25 Amps on each port.
How Much Do You Need?
How much current do you need to get full charging capacity for most phones these days? It depends on the device. Let's use the iPhone as an example - those white chargers that come with the phone are rated at 1 Amp. So, on your drive with GPS running, Bluetooth - and maybe you forgot to switch WiFi off when in the car - your USB adapter .5 Amps of charging current could not keep up with what the phone was drawing, never mind charge it.
What's The Solution?
To get a quick charge on your phone with a low current adapter probably the best thing to do is to power the phone off when charging. That may not be an option though.
Some of the auto manufactures are putting higher capacity USB ports in cars but that does not help most of us driving older cars.
If you want to charge your phone and do not want to buy a new car you can purchase a higher current plug in USB charger. Wirecutter has a nice review of some of these chargers here. A little searching on Amazon brings up a bunch of them too - be sure to check the output current per USB port and compare it to what your phone needs. They're a little more expensive than the $2 ones you see in the supermarket checkout line but worth it.
