More USB chargers doubts

It was slightly less than an year ago that I have vented some doubts about USB chargers and a few more I have now. As I said last week, I changed the ROM on my Milestone and thanks to Robert I have also re-calibrated the battery, with the phone now lasting over a day with a single charge (terrific!).

When doing the calibration, it was suggested to use Battery Monitor to check the status of the battery during the process. The widget itself is quite nice, actually, and has one nice feature that estimates current flow in the device: negative while discharging, positive while charging. This feature is what made me even more doubtful about general usefulness of USB chargers.

I mostly use two USB chargers for my phone: the original one from Motorola, rated at 800mA, and the one I got for my iPod when I bought it a few years back, rated at 1000mA (1A). When I use the Motorola one, the widget shows just shy of 500mA of positive flow… when I do the same on the iPod charger, it shows around 200300. Given the iPod one should have more power than the Motorola one, it shows that something’s wrong.

I remember reading a technical article a few months ago about how Apple enforces their “Made for iPhone” brands on chargers by limiting the amount of current it would require of a charger depending on specifics resistance value over the data lines of the USB port, so that a number of chargers don’t even reach the power of a standard USB port (500mA) when used with an iPhone. Now I’m wondering whether the problem here is that Motorola did the same or if it’s the iPod charger that also tries to “validate” the presence of an iPod on the USB connection. Either way, the option sucks.

It is funny to think that there are so many specifications nowadays that calls for an universal charging solution – just look at this Wikipedia article – and yet nothing seems to stop manufacturers from imposing artificial limitations for the only reason to sell you their own charger!

Of course, simply relying on two chargers, and even more importantly, on the reading of a software application estimates, is no way to draw proper conclusions. The proper course of action, which I wish I had the time to pursue already, would be to add an ammeter in the chain, discharge the phone, then look at what’s really going on in term of current flow during the charge process. My original intention was to add the ammeter after the charger and before the adapter, using male and female USB Type A ports, but nowadays I’m doubtful. Since the European cEPS requirements don’t include the use of a USB Type A charger, but simply of a microUSB connector, it seems like Samsung took the opportunity to provide its users with an old-fashioned charger, where the cable is captive and microUSB is only the connector option.

Given both Samsung and Motorola use Android these days, it wouldn’t be a fair comparison if the two chargers weren’t cross-tested with the other manufacturer’s phone, but that also requires that the ammeter is added in the microUSB chain… option that would disallow testing charging of iPhone and iPod devices since they use the dock connector, and not microUSB.

Any suggestion on how to realise the hardware needed is very welcome, as I’ve already demonstrated I’m not that good an electronics person.

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?

USB chargers and solar backpacks

So today my Nokia E61 battery discharged (after a full charge last night) after a few hours of 3G UMTS connection through bluetooth. I think this means that battery itself is wearing out. I’m considering getting a new one, but an original one really costs too much at the moment (€48!), I’m looking around to see if I can find alternative versions.

Also, I’m thinking to get an USB charger for the E61, possibly a cradle charger. USB would mean I don’t have to hook up a 220->12V converter, which would waste energy unless I unplug it every time; the 220V conversion is already taken care of by Enterprise’s PSU. The reason why I’d like a USB cradle charger is that it’s nicer to have on the desk.

I’m also pondering about replacing the wireless mouse. The one I have now isn’t entirely bad, it’s the one in the LX700 Cordless Desktop by Logitech, but it’s ruining itself, and it’s carged through a 220V converter rather than via USB, I have no clue on why that was designed this way. If anybody can suggest me a Logitech wireless optical mouse with a USB charger cradle, I’ll be considering it seriously.

On a different level, I wonder if anybody reading my blog ever bought a solar backpack like the ones from Voltaic Systems. I’m tempted by this one before summer. I’ll have to see if they support the MacBook Pro charger, but if they do, well, maybe I can use it to power my laptop in the garden, so that I can stay for as long as I want outside rather than inside.

And yes, I do feel green today.