We live in an age where we all have multiple devices that we just can't live without. They also all need charging. This can prove problematic when you are on a long cycle trip and spending a lot of time in your tent a hundred miles from the nearest plug socket. Even when you can find a plug socket you don't want to spending hours each day in a cafe when you would rather be cycling. I have a phone, laptop, kindle, battery pack and head torch that are all require charging. Ridiculous but this is the modern world. It's not a problem if you are spending every other night in a hotel. Often though this isn't an option. If you are spending weeks in your tent on the move in the middle of nowhere then you will need to think about an alternative source of energy. Fortunately there are options. Which option works for you will depend a lot on where you intend to cycle, the terrain, budget and personal preference.
Fast becoming the most popular way to keep charged whilst out on the road. They are certainly the most reliable. Not dependent on weather. You just need to be pedalling. More suitable to flat terrain. If you are up and down mountains all day every day then they are less effective but you should still be able to meet your charging needs. Of course there is no such thing as free energy. You will have to pedal for it. The energy you transfer to your devices will be taken from your legs thus propelling yourself forward slightly slower but the loss in momentum is negligible. Depending on the voltage/efficiency of your hub the drag roughly amounts to a 7/8 minute penalty over a 100km ride. You won't notice it. The only time a drag would bother me is when on a long uphill but here you won't be working up enough speed for it to be an issue. Compatibility can be a problem. I tend to ride and charge just my power bank/battery pack and transfer this to other devices when off the bike. This isn't as efficient as charging the devices directly but it is more convenient. Charging a 5000mAh battery pack will equate to roughly 10 hours of riding. However, there are also small losses in the charging circuitry, so you are looking at roughly 12 hours of riding to fill the battery from scratch. This works for my charging needs.
I like the way the charging unit fits neatly to the top of my headset. They are small, lightweight and easy to assemble. Although do read the assembly instructions carefully. Sitting on the front of the bike all day, everyday you will need to ensure your product is waterproof.
A downside to dynamo hubs is they can be expensive. For the hub itself prices range from $100-$300. Then there is the USB charger unit where prices range from $60 to $150.
I use the Cycle2Charge dynamo to charge whilst I pedal. It was recommended by a friend. Works with all my devices although I tend to just charge my battery pack. It's compact, easy to assemble and it's proven very weather resistant so far. Begins to charge at about 13km/hr. Comes equipped with an overload protection mechanism so all devices are protected against overvoltage and thus damage even when flying downhill. It does not come with a cache so once you dip below 12km/hr the charging will cease. Good value at $60.
Not used it myself but the Cinq5 Plug 3 is recommended by other cyclists. Water/weather resistant and tends to start charging at 10-12km/hr. It is possible to run more than just a USB port from the dynamo hub. To operate lights and the USB simultaneously you can use piggyback spades on your cable. You can even splice your light and power supply cables together into one. From most reports you will need to be averaging over 25km/h to make full use of both your lights and USB. They are quite pricey retailing at $130.
With the Dynamo Hub sitting on your headset you may be concerned that the adapter will prove a problem when flying with your bike and you have to remove the stem. Not a problem though. Underneath the USB port is a cable which can be disconnected easily, allowing you to take your handlebars off without any trouble.
My experience of solar panels hasn't been too successful but the products available are improving all the time. Success very much depends where you are. Obviously you need a lot of sun. If it's going to be cloudy every day then a solar panel will be useless, even the slightest overcast day can mean no charging. In countries with lots of sun you can charge all day. You don't need to be pedalling. They are the most affordable option and depending on the size of your panel most options are pretty lightweight (although heavier than a dynamo hub). A problem I had with mine is that I found for it to charge it had to be angled directly at the sun. This is tricky to maintain when cycling as not only are you constantly changing direction but the sun is permanently on the move as well. I did my best charging with the solar panel when off the bike and I could angle it directly into the sun. Of course the better the panel the better it will be at coping with these limitations. A quality solar panel will have a good interruption recovery speed meaning it will resume charging as soon as the sun hits it again. A cheaper option won't resume at all and you may need to unplug the device and then plug it in again, which can be annoying. Here a few solar panels that come recommended by cycle tourers...
The Goal Zero Nomad 14 Plus is meant to be an excellent charger but it also expensive ($150) and quite bulky (0.9kg).
The Nekteck 21W Solar Charger is a good performer and excellent value at just $50. Weighs in at 0.5kg.
The Anker 15W PowerPort Solar Lite is very popular with cyclists as it's extremely light (0.34kg), affordable ($50) and apparently it also works!
I have just bought one of these. A solar power bank. Not used it yet (will report back) but it is cheap ($25), light (0.3kg) and receives a lot of positive reviews.
Battery Pack/Power Bank
Most cyclists carry a battery pack in addition to their preference of solar panel or dynamo hub. A lot of people now cycle around the world with light laptops. As far as I know there are no dynamos on the market that can charge a laptop (please let me know if I'm wrong). A portable power pack can be a solution. Sadly the rule seems to be the better the heavier and obviously more expensive. I just use a standard, lightweight battery pack ($30) to ensure my phone stays charged when out in the middle of nowhere. My phone is my map, GPS and my music so I can't live without it, sadly. I wish I could! I don't mind my laptop running out of battery. I can live without Netflix for a week or so but if you need your laptop alive whilst out on the road then worth considering one of the following...
The HyperJuice 2 is top of the range and also expensive ($300).
The Lizone Extra Pro has excellent compatibility and a bit cheaper than the HyperJuice 2 ($200).
Tips on saving battery
Obviously it helps if you are not wasting your battery use unnecessarily. Here are a few tips on how to save your battery usage when out on the road.
Don't ask me why but it's never a good idea to charge your phone to the maximum level. Apps like AccuBattery allow you to set a charge alarm to remind you to unplug your phone from the charger once it hits about 80%.
Close your apps.
Decrease your screen brightness.
Keep phone on flight mode.
Set a short screen timeout.
Turn off your Bluetooth/GPS/Wi-Fi/Location services. Obviously we cyclists use GPS a lot but when you are out in the desert and there's only one road to take you don't need it.
Don't listen to music all day every day like I do.
Update your phone’s software and apps. Companies update their apps all the time, often with the features they know their customers need the most, like using less battery life.
Enable Low-Power/Battery-Saver Mode.
Turn phone off in extreme temperatures. Temperatures higher than 35 degrees C can permanently damage battery capacity. In cold conditions, battery life temporarily diminishes but returns to normal functioning once back in its comfort zone.
Limit fetching and refreshing.
Apps that frequently wake up your display screen with notifications will drain the battery.
Use offline maps.
Using Strava via your phone will soon murder your battery. If you want to use Strava get one of those strava watches.
Don't worry about it too much. I have met cyclists who seemed more concerned with their phone running out of battery than they were about running out of food. Look at it this way. If the worst comes to the worst and all your devices are dead then you will immediately be transported into how cycle touring was 30 years ago. No devices. Just you and the open road. Bliss. Sometimes I wish I could throw away all my devices but sadly I am victim of the modern age and I haven't managed it yet. One day!