Yes but no, really as a 1s2p 0.5 amp over two pany 3100 mAh's in parallel is bugger all, but like i said what i linked was more for testing and custom battery packs even charging with a hobby charger, i did not say it was for charging phones did i ?
Now since we are talking about charging phones, i use my car stereo in the family wagon to listen to music and charge our iphones at the same time plus the option of a cigarette lighter socket if tow phones has to be charge at once, good for camping but in our 4X4 i have to use the cigarette lighter socket's or a portable DVD player as the stereo is no iphone compatible its just an oldie as it gets full of sand, mud, dust and water.
At home i normally use 1 of 4 apple chargers we have, or my wifes clock radio iphone dock, or our surround sound system, or xbox or TV or my PC or my wifes laptop, or our blue ray player in the bed room or my daughters DVD player or the portable DVD player.
If I'm out side with mates or in the shed working on cars or what not i use my hobby chargers power supply with a couple of cigarette lighter sockets to charge iphones or ipads cause i normally leave the screen constantly on so i can skip songs and do stuff as i don't like shake to shuffle and i might be out there all day.
Now if i run out of options around the house of in our two cars and i have used all my 20 options to charge an apple product i do not stress i use one of these
MiMi - USB Rechargeable 2000mAh External Battery w/ Stand Feature for iPhone/iPod (Black)
MiMi - USB Rechargeable 2000mAh External Battery w/ Stand Feature for iPhone/iPod (White)
You can buy then to match the colour of your phones isn't that sweet.
Now iphone 4,s will charge from a 0.5 amp device. they like 1 amp as they are a bit hungry, but Ive noticed on some items that only give up to 0.5 amp like 10 inch note pads or net books, old laptops they time out while charging ipads they really need at lest 1 amp but are the most happy on 2 amps half.
Out of the 30 some thing usb ports in my house or cars half will charge at 1 amp and above and the ones i have made personally will do 8 amps each or up to 23 amps over 4 out lets if needed from 12/24 or 240 volt. So charging a phone is the least of my worries i prefer battery packs that are protected so i can test and blow stuff up that is not connected to some expensive electrical item hence my above links.