Charging USB things by bicycle

It’s almost inevitable that if you’re away from home for more than a day, you’ll need to charge something from a USB socket. Phone, camera, GPS, watch (for the slightly more cutting edge), whatever; something with a battery will need your love.

I thought the answer for cyclists came in the form of the Luxos IQ2 U headlight, which combines an exceptionally good headlight with a handlebar-mounted switch/USB socket, all powered by a dynamo hub in your front wheel. It’s still very good, and my review of it remains one of the most popular posts on this blog.

However, with waterproofing niggles that B&M still haven’t sorted after version three, it isn’t the silver bullet I first thought.

Here, then, are a few ideas for powering your goodies if you’re planning a cycle tour or audax. I’m assuming that you’ve got dynamo lighting, because it makes life so much less stressful.

Nothing to charge

Paper maps, old-fashioned phone for emergencies only, AA-powered camera.

Ride on, free of your servitude to the electron (well, ish).


Access to mains power every night

You’re staying in decent accommodation every night, where you can be sure you’ll have access to the mains. Your gear charges as you sleep, with occasional top-ups during the day at handy cafes.

Maybe consider a plug adapter with multiple USB outlets, so you can charge up a couple of things at once if the room you end up in is a little sparse. This thing is £12 on Amazon, and has a decent set of reviews.

Plug with four USB sockets.
The snappily named “TeckNet® Universal BLUETEK™ 24W/5V 4.8A 4 USB Port UK Wall Plug AC Power”. With a name like that, you know it’s good.

Access to mains power at least once a week

Now we’re getting a little more adventurous. We need something to bridge the gap between our access to the grid.

Modern battery banks are like microSD cards – creepy in how much stuff can fit inside.

For example, this EC Technology 22400mAh battery is phone sized, but could charge an iPhone 4 around 15 times before being complete flat. Garmin cycle sat-navs would be nearer 25-30 times.


Most of these also come with a fairly serviceable torch built in. You wouldn’t want to hike with it, but it’s certainly bright enough for rummaging in a dark pannier for dry pants.

Pro tip: try and pick one that can be charged using the same cable as everything else you own (this means not owning an Apple phone, I’m afraid). Also, be aware that these can take an age to charge!

A multi-socket plug is still handy, as then you only have to use the battery if you end up somewhere without mains power.

Be a little careful with battery packs. Don’t get the cheapest, and aim for a brand you’ve heard of (I can confirm my Anker is still good after a few years of heavy use). None are likely to explode, but still… If your trip involves flying check your airline’s rules for loose batteries.

Weeks between mains access

Could you get by with two battery banks? Three? No?

If you really are out in the sticks for weeks at a time then you need to generate power yourself. Abandon now all ingenious thoughts of solar power – it’s just not reliable enough (or weight-efficient).

That power is coming from your dynamo. I still think the Luxos (gratuitous repeated link to review) is your best bet here.

Lusox IQ2 U remote
This is the remote switch for the Luxos (it’s glowing blue because the main beam is on). The bung on the right pulls off to expose the USB socket.

You’ve got other options like the E-werk or Supernova’s The Plug, but the Luxos minimises the wire faff and makes everything very straightforward (as well as giving you a cracking headlight for “free”).

Big caveat: if you’re charging in the rain you’ll need to have the remote switch (and whatever you’re charging) within layers of waterproof bags, because if water gets inside that switch your lights will fail. And I can tell you from experience, that isn’t fun.

Therefore I’d still use a battery bank. The Luxos charges the bank (very slowly) as I ride, and then whenever I stop in the dry something gets plugged in. I know I can get about 15 hours use out of my Garmin 810 sat-nav with the backlight on minimum, so even over a particularly long day on the bike, I could keep the essentials running with a bit of care.

For absolute money-no-object redundancy, I’d be on a trike with dynamos in each front wheel, one for lighting and one for the battery bank. If you can’t face the extra wheel, you could maybe run hub and bottle dynamos.


In summary?

You’ll probably be fine with a chunky battery bank.

If you’ve got any other ingenious strategies (or tales of woe), the comments are just below.


PS: If you’re wondering what I did over the five days and 1,400km of London-Edinburgh-London, I used the Luxos and tried to waterproof both the socket and the cable/Garmin connections using lots (and lots) of electrical tape. You can see this in the photo at the very top of this post – look for the black lump on the bracing strut just above the front wheel. Comments:

  • This almost worked. The Garmin died a few hours before the end (failing legs -> slow speed -> not enough charge for both the light and the USB socket), and I reverted to my printed routecards for the last bit (OK, I mainly followed someone else, but the cards were available…)
  • I couldn’t remove the Garmin from the bike. Happily, because there were so many bikes at each control, the chances of it getting nicked were low.
  • I couldn’t charge my phone which died after four days, causing mild consternation for those following the tweets!


Add Yours →

Worth remembering that the capacity of battery banks (as well as being approximately the most ridiculous excuse for units in the history of engineering…) is the capacity of the 3.7V Lithium battery that runs it – once you step this up to 5V for the USB output, you’re down a fair chunk. That said, noted Youtube electronics-vlogger Julian Ilett reviewed the one linked to here and was impressed.

Also, another vote for Anker’s non-blowy-uppiness here (3 years and counting!)

I’ve flown with it plenty of times, it doesn’t raise any eyebrows…

I built a 5-volt supply myself once with Apple-device-friendly resistors but since discovered a much more compact device ( R-78C5.0-1.0 ) that would do most of the job for me downstream of a rectifier.

I’ve been farting around with ever-more complex circuits for sharing power between USB charging and lights, but the water problem is annoying enough that I’m starting to think a physical switch is a better idea. Simple circuits are waterproof — one I built for use on my kids’ bikes (and that is currently installed on my bike because it was the backup when the wires broke on the other one) continues to work despite being completely exposed to the elements.

Interesting website. Could do with a bit more evidence behind their claims, but looks like a solid alternative.

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