22 May 2014 — NEW TEST INFORMATION ADDED
Though I've helped the handier forum members build inexpensive dynohub-driven USB chargers (see threads in the nearby dynamo charging subfolder), I have little faith in bicycle hubs (SON, Shimano, any of that pattern) being able to produce serious current for serious devices. This is especially so in my own case, because I like to keep the lamps on my bike running in the daytime to help drivers spot me from further out.
In any event, I don't camp; I'm a credit card tourer, and my World Tour of Andre's Little Patch of Beautiful West Cork took all of three days and two nights before I got bored and returned to my desk. The problem is that none of my preferred electronic devices will on the batteries they were born with last that long even with reasonable rather than constant use, and if you have to conserve power by skimpy use you may as well save the weight by not carrying the device. My answer was to pare my device-load and therefore my battery-load down to one device that does everything: heart rate monitor (most important service for my circumstances), phone for emergencies (clearly also tres important), GPS, taking photos and video, music and films, other communications. This is, wait for it, ta-da!
THE iPHONE 4S, SWISS ARMY KNIFE OF SMARTPHONES
The iPhone 4s has a built-in battery of 1432mAh. It is literally a matter of life and death to have a good deal of charge in my phone at all times, as I've been in the hands of the cardio-surgeons twice in the last three years. So my iPhone is backed up by a Mophie Juice Pack Plus (a battery built into a protective case for the iPhone), another 2000mAh, enough to recharge it fully once and have something left over for emergency calls. Together the iPhone’s built-in battery and the Mophie battery case definitely add up to a day's use on, say, a Bluetooth heart rate monitor like my Polar H7 (a belt and sender dedicated to the iPhone), but not enough to have GPS on as well. On rides up to one day (8 hours max between charging points) the iPhone in its Mophie Juice Pack Plus case is normally all I carry. For journeys with overnight stays, I used to carry a charger and a cable.
But a safety margin of say 100% would be even better, just in case the ride stretches beyond the planned duration. It must, though, be instantly available, and that means a battery. In turn, battery weight for capacity being a known if presently changeable quantity, for a cyclist a compromise becomes necessary.
So I bought a battery advertised as 20,000mAh which weighs only 305gr and has USB outputs for 1A and 2A, that is a standard USB device like an iPhone and also (claimed) for an iPad. As you can see below it is not very large, is nicely shaped, with a pebbled leather surface impressed on plastic, about the size of a small travel wallet. It comes with a cable with a standard USB at one end and interchangeable heads, eight supplied, at the other. From the size and experience, I guessed the real capacity to be perhaps 4000mAH.
The battery recharges at a maximum rate of 1A and you can recharge the battery at the same time as you charge devices from it. Clearly, logically, and confirmed by me when I tried it, a battery sucking on 1A will lose the race in recharging a device at 2A. Also by test, the current isn't delivered with enough oomph to charge a monster like the iPad 3rd generation with the high-res screen without the battery being plugged in to the mains for assistance; to my mind that makes the thing worthless as an iPad topup, and in fact I twice saw the backup battery suck juice from the iPad. Twice was enough for me to decide I’ll charge my iPad off the mains, or, more pertinently in this discussion, confirm a prior decision not to take it on tour because the iPhone anyway duplicates all its functions.
The battery recharges the iPhone well, as expected, with or without the wallwart attached. The iPhone is a very fast-charging phone, so the best method of recharging both the iPhone/Mophie combo (which both charge from the same socket in the Mophie case) and the backup battery is to plug the iPhone/Mophie into the backup battery and the backup battery into the wallwart, and let the backup top up the iPhone/Mophie combo until full, and then recharge itself.
The backup battery cost under 10 euro delivered to Ireland -- many soures on the net but I got mine from
http://www.ebay.com/itm/20000mAh-External-Power-Bank-Dual-USB-Battery-Charger-for-iPhone-PSP-HTC-/291096583168.
TEST TO DETERMINE CAPACITY OF 305gr BACKUP BATTERY
Because the Mophie is an unknown, variable quantity, not for being unreliable but for introducing an unknown element of wastage into the equation, I operated the test of the backup battery by running down the iPhone in normal daily use and then recharging it from the backup.
So, on consecutive days, I recharged the iPhone 40% of its capacity, 60%, 66%, 54%. On the next day I tried to recharge the iPhone 63% of its capacity and managed only 17% before the backup battery gave up. This comes to 237% of 1432mAh or 3394mAh. Clearly, there was some wastage, and I guess with the wastage the capacity would be around the 4Ah I guessed.
CONCLUSION
The external battery under discussion is about 4Ah strong, not the the 12Ah claimed. For under a tenner, including postage, I shan't argue about the difference. The claim that this battery, which charges at 1A, could recharge an iPad, I never believed, so wasn't disappointed when it proved untrue.
What this backup battery will do for less than a tenner delivered is extraordinary enough. It will recharge the iPhone 4S, which has the largest battery in Apple's line, nearly three times from 10% to 90%, which by itself could extend use without any access to a wall wart to two days (depending on how you use the device -- I have Bluetooth on permanently, for instance, and Wifi too, and the Polar H7 HRM app, but I don't need GPS as I know my lanes, to give you an example).
In short, for spending ten euro and carrying 305gr, a cyclist could camp away from home overnight without his comms becoming a concern. Or a credit card tourer could run all his apps, including the current-vampires of geopositioning, all day without worrying that he's cutting it so fine that a single flat will leave him without emergency comms.
RECOMMENDATION
Since I was anyway not taken in by the claim of 12Ah, and I never believed a battery that small would have the oomph to charge a monster like the iPad, and therefore limited my expectations to charging the really essential multipurpose device, the iPhone, I'm well enough impressed to recommend a setup customized from mine to their own use to credit card tourers and overnight campers willing to practice the same discipline in limiting the number of current-hungry devices. The photographs tell the rest of the story.
The battery is on the far right. The smaller chrome piece is the sole control button: press it to start the charge, hold it for a couple of seconds to switch the torch on and off. That’s it. There’s no instruction manual whatsoever, not even in chinglish. The longer chrome-appearing strip is the indicator lights. The white cable nearest to the battery and eight adapters came with the battery; I have use for three of the adapters. The USB charger shown is from an Olympus camera kit and is of a type that is both flat enough not to increase the depth of my kit and with legs easily forced into Irish/British sockets; no charger comes with the kit. With the kit as I made it up on the right side of the red line, my iPhone and any other devices I’m likely to take on the road (discussed in a separate post) can be run, and the battery can be charged. I added the two cables on the left, and with them it is possible to charge two Apple devices at the same time as recharging the backup battery from the wall, or to recharge the battery while driving any two of my devices, as long as the current demand falls within the backup battery’s parameters, which, as we have seen, don’t include the hungrier iPads.
No bag is supplied for the battery but, since everyone’s final kit will be different, it’s a good thing that you supply your own bag. The photo shows my minimum kit in the zip-up book-like case, 50 cents at the art store, in which I carry it on the bike; the book format is a useful space saver for me because my devices are generally flat, and so are my sketchbook and paintbox and the various self-contained items in my saddlebag, handlebar bag and panniers (if I carry them; I’m partial to a single pannier basket made by Basil, called the Cardiff, which is on my bike just about permanently). The other cables are just carried loose in the case; normally all three the cables are plugged in when the case is zipped up, with the service ends sticking out so that the case is rarely unzipped. The battery has over-load, over-discharge, etc, protections, so there is no need to monitor the lights, and anyway it takes about eight hours to charge up fully, so that there is little danger of wrecking it if you plug it in when you arrive for an overnight stay and unplug it when you leave the next day.
MY PERSONAL SETUP, TAILORED TO MY CIRCUMSTANCES
So, between the big-battery iPhone 4S, the Mophie Juice Plus Pack extended battery case for the iPhone, and the external battery shown here, when I'm alone on my bike with my iPhone, this kit will let me run the iPhone with Bluetooth going permanently for my heart rate monitor (you choose what’s important to you, but whatever you choose will probably not suck less juice than this supposedly low-energy Bluetooth 4) and intermittent use of other functions as required for at least a very long day away from mains electricity, with amply adequate power left over for any likely and unlikely (Murphy’s Law) emergency calls.
As an example, today the Polar app and Bluetooth (GPS off, eh?) in about four hours drained 430mA, equivalent to 860mA in an eight hour day. 860mA by test takes about two hours to top up from the backup battery to the iPhone, and the idiot lights on the backup battery holds three out of four steady when the power is then plugged in, which seems to promise at least three times that much current still available. (Since confirmed on test, when the capacity of the battery, taken in chunks, was discovered to be 3.4Ah of real, delivered current.)
3.4Ah is a very convenient number for me as my iPhone/Mophie combo is about 3400mAh together, amply beyond the scope of my normal exposure. Effectively it gives me a second day and with double an already ample reserve at the end of it, even if I forget to charge the gear at the guest house or hotel. It also tells us that no credit card tourer need worry that he won’t be able to call home (or emergency services) before he reaches a plug, no matter what goes wrong on the road.
With this kit, an overnight camping trip is not restrained at all by communications concerns. (There goes my excuse for not camping!) A second night away from the wallwart may be possible but could be tight, and the point of my setup, and this article, is to avoid the stress of having the battery in your comms pressure your ride.
Weigh for Mophie, battery, cables, adapters, lightweight zip-up case, around a pound. In touring setup my bike and I scale an eighth of a ton, so a pound's weight for reliable comms is neither here nor there.
God bless the developers of these new battery technologies. This is a piece of kit that adds much more value than it costs.
