See also charging auto and deep-cycle batteries
Under Construction

Mobil Phone Charging:
Manufacturers claim that you should only use their chargers.

Proprietary charging interfaces:
Apple lightning connector
iPhone 5c and 5s and new iPads have "lightning" connectors for charging one end is a standard USB connector and the other is a proprietary connector.
Only some versions of 3rd party lightning connectors authorized by Apple will work.
The lightning cable has a chip in it which is required for it to work.
See iOS 7 now blocking some third-party Lightning cables | 9to5Mac

Work around at iPhoneHacks.com
1. with phone on plug cable into wall or laptop
2. see message above
3. press and hold power button
4. turn phone off
5. phone will cycle back on automatically
6. lock screen will show warning message but this time the phone will be charging
7. unlock phone and it will still charge.

I also had problems with some USB power supplies. A 1 amp belkin (120 V) and a .750 amp Belkin (12 V) did not indicate that they were charging my iPhone 5s with iOS 7 and the cable supplied by apple. But they were; The percent charged kept going up very slowly.
A 2 amp ASUS worked as did plugging into my PowerBook. It also worked with my HyperMac external power supply.

"Motorola Razr:
The motorola Razr may give you an "unauthorized charger" message with third party chargers.

The USB specification limits the minimum power available from the interface voltage pins to 500 mA at 5 volts, or 2.5 W. The GSM version of the RAZR, which first adopted the USB charger cable, can apparently live with that, but the CDMA phone is more power hungry and needs more than 2.5W to charge. The chargers supplied by Motorola will deliver significantly more than 500 mA, and as a practical matter a lot of other USB chargers and interfaces will too, but with the latter you can't count on them to support more than the standard requires.

It may or may not still charge the phone, you'll have to try it to see. If it does charge the phone it will take longer to do so than a higher power charger would.
Source: Dennis Ferguson at www.wirelessforums.org

Another person said "I'm not sure that's all there is. My wife has a V3c, and I tried a Zip-Linq USB power supply rated 5V @ 1000 mA and got the same error message."

Had similar experiences with another phone and just kept exchanging them at Wal-Mart until one worked.

Cables:
USB Mobil Phone Charge Cables
how-to make a usb battery
How USB charging works, or how to avoid blowing up your smartphone | ExtremeTech
Why Apple CouldnŐt Go to Micro USB Charging | Tech.pinions - Perspective, Insight, Analysis

Voltages:
Some devices can run from substantially higher voltages than the rating of their standard plugpack. This lets them deal with unregulated plugpacks whose voltage only drops to the rated figure when the plugpack's delivering maximum current. Don't bet on any particular gadget being able to do this, though. If you over-stress a regulator, it can easily overheat and die.
Source: USB Mobil Phone Charge Cables

Sample charging requirements:

Mobil Phones - radios
Motorola V330         5.9V 375 mA
Motorola RAZR V3c     5 V  500 mA
Plantronics Headphone 5 V  180 mA
Kenwood HandiTalkie  13.8 V 650 mA

Laptops
Apple PowerBook G4 24 V 1.9 A
Toshiba Portoge    15 V 2 A
Other Computer:
Card Reader HD      5 V 800 mA
LaCie Firewire     12 V
Canon PIXMA iP90 printer  16 V 1.8 A

Firewire 7-30 V

Other:
Canon ZR90 digital camcorder 8.4 V 1.5 A
Magellan eXplorist 500 GPS   5   V 1 A
Sony CD MP3 player           4.5 V 500 mA
See Also Power requirements in Home & Garden

USB battery power packs:
www.ladyada.net/make/mintyboost/make.html
www.usbgeek.com/prod_detail.php?prod_id=0347

Chargers:
Products page - Batterytender.com


Links:
How USB charging works, or how to avoid blowing up your smartphone | ExtremeTech
charging auto and deep-cycle batteries
Batteries in Home & Garden.
Charging at Deep Cycle FAQ
Charging the lead-acid battery - Battery University
12 V power for ham radio
The charge of the mobile phone brigade by Graeme Philipson
Hand Crank flashlights and Mobil Phone Chargers
Solar Panels
Power requirements
Surge Protectors
Uninterruptible power supply
CTEK Multi US 3300 12V Smart Battery Charger Review

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last updated 14 Apr 2008