How to choose the Powerbank for bike trips and how to recharge it on the go: solar panel and dynamo
Even if you are a lover of traditional paper maps, between your mobile phone, GPS, lights etc., you will need a way to recharge your devices’ batteries.
In addition to the standard wall “socket” during breaks, the powerbank is the only real solution, but how do you choose the best powerbank for long bike trips?
Let’s look at the technical characteristics of powerbanks and how to recharge them to help you make an informed choice.
The main features of the powerbanks:
Watt: is the unit of measurement of power, i.e. how much a device consumes. The maximum power is marked on all devices. In reality, a device will always consume less than what is written (so let’s not blindly rely on the duration advertised in the product description but focus on the wattage written on the back).
In mathematical terms, it is expressed by the product of voltage and intensity. Therefore W= V*A.
Voltage: is expressed in volts and is the strength of the current which (distributed continuously) is needed by the device to make it work. Typically, when you plug into a socket with fewer Volts than the phone (below 5V), it won’t recharge. To avoid damaging the batteries, using a powerbank with the same Volts as those marked on your devices is always better.
Amperage: it is expressed in Amperes and is the amount of energy that is transmitted. It determines how long a powerbank takes to recharge a device.
Milliampere-hour is basically how much electricity the powerbank can store: its unit is mAh. We can say that it expresses the “capacity” of the battery.
Ok, now that we’ve sat through this technical list, how do we choose?
First, let’s look at how many Volts our devices need (not together) to function and recharge. If your phone typically needs 5V, cameras and lights may have less power. Voltage is essential to keep the battery healthy, but don’t get too excited: even if it’s recommended to keep the voltage the same, you can’t carry around a different powerbank for each object, so find an average.
Since you’ll be charging your phone more than anything else, stick to 5V.
As we have seen, the Amperage is a more helpful metric: 2 A are sufficient. There are now many powerbanks on the market that promise faster charging: this is determined by an output with higher Amperage.
How big to take it? The advice is to stay above 20,000 mAh – it should be enough to recharge a phone 4 times, and maybe even more.
Recharge: the solar panel and the dynamo for cycling trips
But how do you recharge the powerbank?
The explanation of this question is beneficial for us when we are on the road.
Even the powerbank is a device with an input, i.e. with a precise electrical charging requirement. If the recharge output is too low, recharging your powerbank will take a long time. Then it just ends up as a cumbersome brick in our bag. As you may have guessed, we need to understand what amperage our solar panel or dynamo works at.
There have long been plenty of portable 2- or 3-sheet solar panels that you can fit on top of your rear bag or handlebar bag. We tested this one from Decathlon, which could be more compact, but it gets the job done.
How big does the panel need to be? Not very large. The surface area of the solar panels determines the Wattage, i.e., how much energy it can consume. The material is more important: those in monocrystalline silicon provide greater power than those in polycrystalline or amorphous silicon.
The dynamo for bikepacking
How to understand how long it takes a solar panel to recharge the powerbank?
A 20W panel has an amperage of 1.28A (=1280mA).
If our battery has 20 000 mAh
20000 / 1280 = 15.6 (hours)
Long time right? Keep in mind, however, that a day on the road is easily made up of 10 hours, and therefore you will have those hours of sun exposure (in summer). It won’t charge you all the way, but you’ll make it to the next charge point.
Cost: various. From Decathlon, it costs around €40. The most popular is that of Anker, PowerPort Solar, which costs €70.
Sure, but what if it rains? Or if it’s cloudy? The charging time via the solar panel will increase because fewer Watts will come from the sun.
The hub dynamo doesn’t have these problems because it creates electricity from the movement of your front wheel. So even if you just don’t see the sun for 4 days, you’ll still have electricity. The dynamo is most often used for lights, but it can be used, with a power converter, to generate electricity for use elsewhere – like recharging a power bank.
Let’s redo our calculation:
More or less all dynamos require a minimum of about 2W to start recharging, and we can estimate that you have to pedal at about 13-14 km/h to start it.
The dynamo must then be connected to a small transformer which outputs a power of about 5V at 500mA therefore:
20,000 (the capacity of the power bank) /500= 40 hours
As you can see it will take you a while, but the efficiency of the dynamo lies in the fact that at higher speeds, the amperage increases and, therefore, reduces the time it takes to recharge your powerbank. The obvious advantage is that you’re still producing energy, even if it’s cloudy.
In terms of friction and drag, many studies have been done, and the slowdown caused by the hub dynamo is minimal.
Costs: The dynamo system + power converter will cost you around €400-500.