Charging your phone while cycling

Some consider them a curse, but it’s very hard to argue against the very real benefits smartphones bring to our lives. Whether it’s accessing social media, or taking a photo, most of us are using our phones all the time, and that simply means it’s quite easy to totally drain your phone’s battery during a normal day’s usage.

When we throw battery-sapping uses, like using GPS, or the camera, into the mix, then your phone’s battery life off a single charge could be reduced to just a few hours. Add to that the fact that a good bike ride can be far longer than just a few hours, and the scale of the problem becomes instantly obvious. And that’s before we even think about multi-day rides!

So, what practical steps can you take to guard against having a flat phone battery? Well, you really only have two options: use a power bank, or use a dynamo.

We’ll give it a minute for the laughter to die down, after that one person at the back suggested solar charging as an option anywhere outside of the Namib desert.

The power bank option

Power banks have long outgrown their initial niche and geeky status, and most supermarkets stock them now, but do yourself a favour and don’t rush out to buy one of those. I’ll explain why in a bit.

You will probably have heard of Anker power banks – they’ve built up a reputation for quality products. This is the point where you expect me to suggest you buy an Anker power bank, right? Only, I’ll do the opposite, and suggest you avoid Anker, at least until you’ve read this entire post, and had time to consider your options.

Yes, I know I just said they make good products, and they really do, but not all power banks are the same. Some support something called pass-through charging, and others don’t. Specifically, Anker power banks don’t support pass-through charging.

What is pass-through charging, and why should you care about it? I’ll answer the last part of that question first: it depends on your future plans. If at most what you’ll be doing is go for a bike ride of a few hours, every so often, and you have no plans of going beyond that, then please do get an Anker, or any other make.

However, if there’s even the slightest chance that you’ll be doing longer, or multi-day rides, or that you might upgrade to dynamo lights at some stage in the future, then I strongly suggest you get a power bank that supports pass-through charging.

As for what it is, that’s simple: a power bank that supports pass-through charging can simultaneously be charged, and be charging something else. If you’ve stopped in a café, on a tour, with a phone that’s almost dead and a power bank that’s depleted, but there’s just one socket to plug into, you can plug your charger into the power bank, and your phone into the power bank at the same time. Both the power bank and the phone will start charging, but at a slower rate than if only one device was being charged.

That pass-through charging ability can make an enormous difference. Sadly, power banks are rarely sold with a clear indication of whether or not they support pass-through charging, so when I need to buy one, I ask the site to explicitly tell me. That way, if it doesn’t support pass-through, I can return it for a refund.

In terms of capacity, just don’t bother with a power bank of less than 10 000 mAh (milli Amps per hour) and ideally try to get a 20 000 mAh one. Trust me, you’ll thank me later!
The mAh rating is a measure of the charge capacity of the power bank. If your phone has a 2 500 mAh battery, in theory, a 10 000 mAh power bank can fully charge it up four times. Because retrieving stored electricity from a battery, and storing it in a battery consumes some energy, you’ll never get the full value, but if yours is a hefty power bank, it shouldn’t matter.

Next get a handlebar bag, or one of those nifty top-tube bags, to carry your power bank in, when going for a long ride. Many such bags also have a see-through top panel, so you can have your phone in there and still operate the touch-screen. Just be aware that most such bags aren’t waterproof, and you really don’t want your phone, or your power bank to get wet!

For that reason, you might want to invest in a splash-proof bag to keep you phone in, once it starts raining.

The dynamo option

Here’s where things get interesting! Go on, embrace your inner geek!

A dynamo is just a generator that uses your muscle power to generate electricity. You mainly get two types: the old-fashioned bottle dynamo, and the far better hub dynamo. A bottle dynamo is called that, because it looks like a bottle. It sit’s in a spring-loaded cage, and when released, the “cap” of the bottle rubs against the sidewall of the tyre. Fitted correctly, they shouldn’t wear the tyre out, but they are noisy!

Hub dynamos are called that, because they’re inside the hub of the bike’s front wheel. When the wheels start turning, the dynamo starts generating electricity.

Some people will tell you of dynamos causing extreme drag, and therefore both slowing you down and tiring you out, and I’ll tell you now they mainly talk nonsense.
Strictly speaking, dynamos do slow you down, but far, far less than you think, and you will not be able to feel the difference when out cycling. It isn’t free power, as such, but it comes close!

Some clever people did some lab tests, with surprising results. The short version is is this: a dynamo slows you down far less that you will have guessed. If you clicked the link above, and read the article, you will have read this bit: “The most efficient dynamo hubs when switched ON add between 3min 24sec and 5min 47sec to a flat ride over 100km when compared to a regular hub.

I always factor the worst-case in when doing calculations, and in this case it means my dynamo can slow me down by as much as one minute per 10 miles. To me, that’s negligible, and given how much my dynamo benefits me, I’ll happily take that as a win.

To get a hub dynamo, you either have to rebuild your wheel around a dynamo hub (which is what I did) or you have to replace it with a complete wheel that was built around a hub dynamo. In terms of brands, there are a fair few, with Son making the best (and eye-wateringly expensive!) dynamos, and Shimano making marginally less efficient, but far cheaper ones. Mine’s a Shimano.

Now you have a dynamo, so now what? Electricity comes in two forms: AC (alternating current) and DC (direct current). A dynamo delivers 6V AC, while your phone needs stable USB, which is DC. This means we need some gadgetry to convert AC to DC. That’s a simple affair, using two diodes, and a capacitor, but stable USB power requires far more, and electronic gadgets are quite sensitive to how they’re being charged.

Some dynamo lights, such as the superb Busch & Muller Lumotec IQ2, includes the gadgetry, and offers safe and stable USB power, but most dynamo lights don’t. If the dynamo lights you’re getting (because why turn your nose up at a dynamo’s greatest benefit) doesn’t offer USB-charging, then you’ll need an additional gadget.

There are many plans and schematics on the Internet, for those who want to build their own, but most people simply want to buy a gadget that’s ready-made. Top of the list is probably the Reecharge kits, but lately those seem to be out of stock everywhere. They’ve also come down in price a great deal.

If you can find one, then by all means buy it . It should come with simple schematics to wire it up, but you must understand that a bicycle dynamo cannot supply enough power to both charge an electronic device, and run your lights. It very much is an either/or situation.

And this is where we revisit your choice of power bank! If you bought a power bank that does pass-through charging, you will take the USB power from the dynamo’s gadgetry and charge up your power bank during the day, when you don’t need your lights. At night, if still cycling, you can use your lights, and rely on the power bank to charge your other gadgets.

The way I do it is I take the power bank into my tent with me overnight, so my phone and Garmin charge up while I’m sleeping.

If you cannot find a Reecharge in stock anywhere, don’t worry, as you still have options: You can simply click this link and buy a ready-made device, for under £30. A more expensive, but certainly better option is the Busch & Muller USB-Werk. That used to be available online for better prices, but the suppliers no longer sell directly to the UK, it seems.

Though discontinued, you can also still get Nokia DC-14 kits, which come with a bottle dynamo. I used to have one, and wrote about it before.

And there you have it – phone-charging on the go. On rides with just a single night’s camping, I used to simply rely on a power bank, but my Garmin is an Edge 500, is old and rather primitive. I recently changed my phone to a waterproof one, and I now have a handlebar mount for it. I’m increasingly relying on my phone for navigation, running the excellent RideWithGPS app

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