To answer some questions for myself I cannibalized a usb extension cable, shortened it to about 6 inches and left the red +5V line open so I could use an ammeter to check current levels using different cables and devices. The results are basically "duh" and many of you wont be surprised by any, although I did clear up a few misconceptions I had.
I have several 10' charge/sync cables from dealextreme that have worked very well for my iPhone, but when using them with my new ipad the math just didnt add up and the charge was slow.. anyhow, here are the results:
IPAD RESULTS
10' cord - maxed out at 1.4 amps. I cut it down to verify length was the only limiting factor. It was.. it maxed at 2.0a when I cut it to about 3 feet.
Stock cord - 2a max. I did NOT cut it down to see if I could get that up to the 2.1a rated capacity of the charger.
Also interesting (yet expected) as the ipad nears a full charge the draw decreased (I'm going to do a time lapse and I'll graph it to get exact numbers). When the screen was turned off, the draw would drop about .2a (not when the charge was low, it maintained the 2a draw).
IPHONE 4S
I know a lot of people have said the iPhone will charge faster on the ipad charger due to the available extra current, however my iphone4s only drew a max of 1a on both the ipad3, iphone, and aftermarket charger (same ipad stock cable for all three), so there is clearly a limit set in the phone. On the bright side, it confirms Apples statement that it is perfectly ok to use either charger (even though 2a would still be safe for the lipo battery as many have mentioned). Unless there is new math I dont know about, there is no way the ipad charger charges the iphone4s faster... the phone is the limiting factor. When the phone reached 100% the draw dropped to around .2a and was variable dependent on brightness and what kind of load the A5 was handling, ect.. basically everything you'd expect to ding the battery.. Also, when you turn the phone off, current drops to zero for a second or two, then jumps back up to whatever the charge rate was when it was on, so it's clearly "smart" circuity whether the phone is on or off.
Like I said, none of this is particularly shocking.. It should be no surprise that a piece of technology like the iDevices would have very specific charge curves and hard limits to protect itself. The one thing that I didnt expect was the iphone hard cutoff at 1a.. I too thought my ipad charger worked quicker, but I cant ignore the numbers and chalk it up to wishful perception..
SOOOOO....
If your new ipad is charging slow, make sure you are using the stock charger and the stock cable... My 10' cables are awesome for in bed and at work as the length lets me keep everything at 100% without feeling tied to a short leash, but they just barely keep up with the ipad when it's in moderate use.
Hope this helps at least one person.
I have several 10' charge/sync cables from dealextreme that have worked very well for my iPhone, but when using them with my new ipad the math just didnt add up and the charge was slow.. anyhow, here are the results:
IPAD RESULTS
10' cord - maxed out at 1.4 amps. I cut it down to verify length was the only limiting factor. It was.. it maxed at 2.0a when I cut it to about 3 feet.
Stock cord - 2a max. I did NOT cut it down to see if I could get that up to the 2.1a rated capacity of the charger.
Also interesting (yet expected) as the ipad nears a full charge the draw decreased (I'm going to do a time lapse and I'll graph it to get exact numbers). When the screen was turned off, the draw would drop about .2a (not when the charge was low, it maintained the 2a draw).
IPHONE 4S
I know a lot of people have said the iPhone will charge faster on the ipad charger due to the available extra current, however my iphone4s only drew a max of 1a on both the ipad3, iphone, and aftermarket charger (same ipad stock cable for all three), so there is clearly a limit set in the phone. On the bright side, it confirms Apples statement that it is perfectly ok to use either charger (even though 2a would still be safe for the lipo battery as many have mentioned). Unless there is new math I dont know about, there is no way the ipad charger charges the iphone4s faster... the phone is the limiting factor. When the phone reached 100% the draw dropped to around .2a and was variable dependent on brightness and what kind of load the A5 was handling, ect.. basically everything you'd expect to ding the battery.. Also, when you turn the phone off, current drops to zero for a second or two, then jumps back up to whatever the charge rate was when it was on, so it's clearly "smart" circuity whether the phone is on or off.
Like I said, none of this is particularly shocking.. It should be no surprise that a piece of technology like the iDevices would have very specific charge curves and hard limits to protect itself. The one thing that I didnt expect was the iphone hard cutoff at 1a.. I too thought my ipad charger worked quicker, but I cant ignore the numbers and chalk it up to wishful perception..
SOOOOO....
If your new ipad is charging slow, make sure you are using the stock charger and the stock cable... My 10' cables are awesome for in bed and at work as the length lets me keep everything at 100% without feeling tied to a short leash, but they just barely keep up with the ipad when it's in moderate use.
Hope this helps at least one person.
