Why Won’t My MiFi Charge?

I recently purchased a Novatel MiFi 2200 on Virgin Mobile (USA) as an emergency fallback networking device for Tech Field Day, and it saved our bacon on-site at Symantec.

It literally saved our bacon. See, being a security company, Symantec had a strictly-controlled network that did not allow live streaming to Ustream. Since the CradlePoint PHS300 was in use by the delegates, we were forced to send the live video stream over 3G. If the MiFi wasn’t available, no one would have heard the delegate requests for bacon at future sessions!

But the MiFi only lasted a few hours before the battery ran low. This is when I discovered the obnoxious design flaw: The MiFi 2200 requires a special charging cable. The bundled charger works, but normal folks (like me) might assume that any Micro-USB cable will work. They would be wrong.

A quick Internet search reveals that I’m not alone in my frustration here. My friends over at the EVDOForums have documented that the MiFi puts 1.4 volts on “pin X” of the USB cable, just like certain Motorola devices. Although any old Micro-USB cable will fit (including the one from my Jawbone Icon) it will not charge the battery.

Unlike the iPhone and iPad, which sense charger amperage using resistance across the data pins, the MiFi and Motorola require a voltage on a normally-grounded pin. This seems a less-elegant design, implemented with a simple resistor between pin-X and ground.

What Works

The solutions are simple but annoying:

1. Don’t run the battery down – This is an option for casual users, but I’m not one of those.
2. Install the drivers and charge from a laptop – This is probably the simplest solution, since the MiFi will supposedly charge from any cable on a PC when the drivers are installed. But it didn’t work with my MacBook Pro, takes much longer to charge anyway, and requires a powered-on laptop.
3. Pack the official/original charging brick/cable – This dramatically increases the travel bulk of the MiFi, which is a common complaint with ultra-portable devices.
4. Get an appropriate cable – I haven’t tried this exact cable, but a proper Motorola Micro-USB charger cable should work.

The MiFi also requires a fairly powerful USB charger: Reports say it draws 800 mA when charging, so many old 500 mA chargers (and PC USB ports) won’t cut it even with the proper cable.

What Doesn’t Work

I’ve tried a wide variety of USB power sources and cables and was not able to get the following to work:

1. Cables
   1. A plain-jane USB to Micro-USB cable I had lying around
   2. The cute and short USB to Micro-USB cable that came with my Jawbone Icon
   3. The tiny Mini-USB to Micro-USB adapter that came with my Motorola H800 bluetooth headset
   4. A BlackBerry-brand USB to Micro-USB cable I didn’t know I had
   5. The “power-splitter” Mini-USB cable that came with a Seagate portable hard drive
2. Chargers
   1. The original 1 A iPhone USB brick
   2. The tiny 1 A iPhone 4 USB brick
   3. The 2.1 A (10 W) iPad USB brick
   4. A Staples-brand mini surge protector with USB power ports
   5. The USB ports on my MacBook Pro (even after installing the drivers)

In summary, both the cable and the charger need to be right. You can’t just plug in a 1 A Micro-USB cable and have it work. It has to have the special “Pin X” magic.

Stephen’s Stance

It was nice to hear vendors talk about making Micro-USB a standard for portable devices, but it would have been nicer if they actually standardized the pinouts and sensing scheme as well. An average consumer will be frustrated when they plug in a device and it won’t charge, and will likely assume that the device is defective.

Plus, now I have to carry along the MiFi power brick. I hate that.