Best USB Car Charger

PowerGen Car Charger

You purchased a "fast" car charger for your mobile device (smartphone, tablet, etc), but you find that the actual charging rate is slow, possibly not even able to keep up if you use the mobile device at the same time. What's up with that? Is the charger defective? Not really a "fast" charger?

It's the fault of the USB standard, not necessarily the charger. USB was conceived as a connection standard, not a charger standard, and to keep costs down the original standard provides only a modest amount of power, a maximum of 500 mA. But as USB gained traction as a connection standard, it also gained traction in chargers.

500 mA (½ A) is fine for a low power device like a mouse, but insufficient for fast charging of a current smartphone (~1000 mA), much less a tablet (~2000 mA). The USB standard is evolving to deliver greater amounts of power, but adoption takes time, and current USB products could be damaged by high power drain, so device manufacturers have resorted to non-standard tricks for fast charging with USB connectors:

1. Shorted data connection: This is frequently used by Android devices (e.g., Nexus 5), which won't try to fast charge if the data connection isn't shorted, displaying (USB) rather than (AC) on the Battery screen.
2. Non-standard data voltage: This method is used by Apple devices, with different voltages signaling different maximum charging rates. They similarly won't try to fast charge when those voltages aren't present.

Since no standard USB port should do these things, a device can assume it's on a charger rather than a USB host. But since there is no single method, and since both methods can't be used at the same time, a charger that's fast for Apple devices may not be fast for Android devices, and vice versa. So either make sure to choose the right type of charger (which can be tricky), or choose a charger that has both methods, like the excellent PowerGen 4.2A/20W Dual USB Car Charger:

• High power for fast charging even tablets
• Dual ports for charging 2 devices at once, one Android port and one Apple port*
• Good physical design for secure fit and durability
• Compact size
• Great value: $10 at Amazon.com

PowerGen Wall Charger

Best USB Wall Charger

All of the same considerations apply, and PowerGen comes to the rescue here as well, with the PowerGen 2.4-Amp (12 Watt) Dual USB Wall Charger. Another great value: $13 at Amazon.com

UPDATE: There is now a more powerful version: PowerGen 3.4-Amp (17 Watt) Dual USB Wall Charger. Even better value: $10 at Amazon.com

* If a device is connected to the other type of port, it will still charge, but the rate may be slow.