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Hardware doubts: USB-based chargers

It seems like a huge number of phones and general portable devices, nowadays, charge with the help of USB-based chargers; these usually consists of extremely compact devices with a power plug, and an USB socket (type A) and come with a standard USB cable (usable for data as well as pure power) using either type mini-B (for older models) or micro-B (for almost all modern models, as they seem to have standardised with the help of the Open Mobile Terminal Platform).

I have to note that sometimes, even if the charging happens over the USB port, the manufacturer provides you not with a generic USB charger, but rather with a (sometimes model-specific!) charger that have from the terminal side the proper mini- or micro-USB plug, but is hardwired into the adapter. Motorola used to do that at the time of the V3 models (and many others; including their Bluetooth headsets; I got a very old, very cheap one yesterday for my Milestone), and Samsung seems to be doing that, at least with the Corby.

At any rate, this is actually handy: I can leave a single charger in my bedroom, and one ready in my bag; then have around just a few cables (one for the iPod, one for the Milestone, one for the BT headset). On my office, I use the USB ports on my computer to charge them; this wouldn’t work as well, if I didn’t have this nice Belkin HUB that provides even ports with half an Ampere per port (the maximum standardised by USB); without that it would split the 500mA between multiple ports, and then it would take æons to charge.

But while travelling the past weekend to be at a fair to help some friends out, I noticed that sometimes, I really need to charge both the iPod and the cellphone, and bringing around a single charger while handy stops me from doing that. Luckily I remembered that a friend of mine suggested that there are many dual-USB chargers out there. I found some by Belkin as well, in a Saturn store near here, but unfortunately they seem to have a different problem.

As I said the computer USB ports are rated at an output of 500mA; on the other hand, the charger that Motorola gave me with my Milestone is rated for 850mA, and the iPod charger is rated at 1A (1000mA). This is pretty useful, as the higher current should allow for faster charge… and still not burn anything out. So, looking at dual-USB wall chargers, you’d expect them being rated for total output of 1.7A-2A, so that each port can output the equivalent current to the single-output chargers. But browsing through the above-mentioned store, I noticed that about half of them are rated for total output 1A (0.5A per-port, like a computer) and half of them are not rated at all on the box, or not clearly. For instance, the Belkin ones say they have “two USB 1A ports”, can’t really tell whether the charger has two 1A-ports or two ports for a total of 1A.

I hate when the specifics on the boxes don’t really make it explicit what you’re going to buy. Does anybody know these products and can shed some light over the matter?

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