How to choose a solar charger that even a cultured hiker can easily understand

New mountain gear that will be essential for the outdoors in the future

Smartphones, digital cameras, GPS, outdoor watches, tablets...electronic gadgets have become regular fixtures on our equipment lists over the past few years

These not only improve safety and convenience, but have also become essential mountain gear for new ways of enjoying the outdoors, such as recording and sharing photos and text. Meanwhile, with Wi-Fi installation experiments under consideration in the Northern Alps , there's no doubt that the use of digital devices will also become commonplace in terms of mountain safety.

However, carrying around so many electronic devices has also created a problem: charging the devices when the battery runs out. For day trips or overnight hikes, standard lithium-ion batteries sold at electronics stores are sufficient if you charge them at home. However, hiking over several nights is a different story. You'll always need to charge them somewhere, and they have the drawback of significantly reducing performance during the cold, snowy season

Where should I focus?

So, this time I focused on solar charging, which is currently the easiest way to generate electricity outdoors. Although information about this new field can be found in various digital gadget media, there are currently very few guides or review articles that can be used from an outdoor perspective. In addition, as I realized while researching, there are many topics that are difficult for a culture-oriented person like me to understand

So, in this article, I've unraveled these complex and difficult mechanisms so that even we artisan hikers can understand, while boldly cutting out the more technical parts and summarizing the key points to keep in mind when choosing the best solar charger. Please use this as a reference if you're thinking of using a solar charger. However, I'm an arts person after all, and I'm not particularly well-versed in the hard-core science and engineering field of solar power generation. I'm happy to accept criticism from experts. If there are any errors, please let me know and I'll correct them.

Just to be clear, we cannot take any responsibility for the accuracy of the content, safety, or any malfunction of your device, so please make your final decision at your own risk

Step 0: Before purchasing: Do you really need a solar charger?

Before we move on to the topic of solar chargers, let's organize the various methods for charging outdoors where there are no power outlets. This will help you understand the best charging method for your purpose and situation, as well as give you a general idea of ​​the best solar charger to choose

Summary of common outdoor charging methods

type	Mobile battery	Mobile battery with solar panel	solar charger	Integrated battery solar charger
Features	Portable battery that can be charged via a power outlet or USB	A power-generating mobile battery with a solar panel on its surface	A charger equipped with a solar panel that generates electricity more efficiently and charges in real time via an output terminal such as USB	A solar charger that combines a solar panel and battery to generate and store electricity
Reference image
Power generation	×	△	◎	◯
Electricity storage	◎	◯	×	△
capacity	◎	◯	×	△
merit	High power and large capacity Stable charging possible	High power and large capacity Stable charging possible Solar panels can generate and store electricity	Large solar panels enable highly efficient power generation High output depending on sunlight (unlimited capacity)	Relatively large solar panels enable highly efficient power generation Power storage possible (When charging from a storage battery) Stable charging is possible Since no external cables are required for power generation and storage, electricity can be stored relatively efficiently
Disadvantages	If the capacity is used up and there is no power, it's over	Generally, solar panels have poor storage efficiency	Without sunlight, nothing can be done Cannot store electricity	Generally, storage batteries have low performance (if high performance is required for both, the size will be large and heavy)
Ideal for outdoor scenes	Camping, day trips and overnight hikes	For disaster preparedness, camping, day trips to overnight hikes	Hiking on trails with plenty of sunlight, long-term treks of two nights or more (permanent base camps are even better)	Perfect for camping, day hikes, long-term trekking, and more

As shown in the list above, for people who usually only go on day hikes, there is little

Also, while mobile batteries with attached solar panels are solid as mobile batteries, the charging efficiency of the solar panels is often poor, and they are currently considered to be merely a bonus. While they are ideal for emergencies, it is difficult to rely on the solar power for outdoor use.

Solar chargers are most useful when you need to charge many electronic devices and your mobile battery simply doesn't have enough power on a long trip of two nights or more . They're even better when you're settling down at a base camp or somewhere else where you can leave it in a place that gets plenty of sunlight, or when you're on a ridge or other area that gets a lot of sunlight for long periods of time.

As we will explain later, solar chargers generally do not have the function of storing (accumulating) the electricity they generate, so in reality, using them in conjunction with a mobile battery or choosing a solar charger that is integrated with a battery will allow you to generate and store electricity efficiently, making this the most effective combination (see photo below).

Various methods of storing electricity. From the left: combined use with a mobile battery, nickel-metal hydride battery, and built-in lithium-ion battery

Step 1: Select the output ~ Is it a mistake to think that "high output means fast charging"?

Even if the charger has high output, the charging speed will not increase

When choosing a solar charger, the first thing you're probably concerned about is how powerful and efficient it is, in other words, how quickly it can charge

The power of a charger is generally expressed as the amount of output that can be supplied from the charger to an electronic device, and refers to the unit of power called "watts (W)." As shown in the formula below, power is the product of current and voltage, and the higher the voltage and current, the greater the output. This is the basic premise for knowing the specifications of a solar charger, so please remember it, even though it may be a hassle

Power (W) = Voltage (V) × Current (A)

Solar charger products are often full of slogans such as "high output of 15W" and "fast charging at up to 3A," and it's safe to assume that they are spoken with these formulas in mind

If you think about it normally, you might think that the higher the power of a charger, the faster it will charge (like I did a while ago). While this is not wrong, when it comes to the electronic devices around us, it is not actually that simple

This is because, no matter how high the charger's maximum output (= the maximum power it can supply to a device), it cannot supply more power than the receiving device specifies . Furthermore, the cable connecting them must also be capable of carrying that current. Therefore, the following principle serves as another basic premise.

Three conditions for high-power charging:
1. A high-power charger.
2. A device that supports high power.
3. A cable that supports high power.

Choose the output that best suits the device you want to charge

So what is the output power required by the receiving electronic device? For reference, we have compiled the charging power output of common electronic devices based on the figures printed on the original adapter

Generally, small electronic devices such as smartphones only require an output of around 5W, and devices that require higher power, such as tablets, can handle outputs higher than that. Incidentally, there are also devices that can only handle even lower power, such as smartwatches

What we can see from the table above is no matter how high an output solar charger you have, if the device you're charging doesn't support that high output, it will all be wasted (devices generally automatically adjust their maximum output to charge*). If you only need to charge a smartphone, there's no real need for an output of more than 5W.

Recent high-output models tend to have multiple ports

One thing to note here is that everything we've discussed so far has been about solar chargers with one charging port (USB outlet). If there are two charging ports, as in the photo above, the charger's maximum output represents the combined output of each port , so in that case it's very useful in the sense that you can charge multiple devices simultaneously at optimal output. What's important is what the maximum output value means. Make sure you check this carefully so you don't get fooled.

*When charging, if a device that requires an output different from the charger's output is connected, most chargers have a safety mechanism that will detect the abnormality and shut down, but depending on the device, there is still a possibility that it could be damaged, explode, or catch fire in the worst case scenario. Of course, when using, be sure to follow the instructions and directions for each product, check that the charger and electronic device are not abnormally hot, and take great care not to leave them connected or out of sight

Points to consider when choosing

• The higher the output of the solar charger, the faster it can charge, but the receiving battery and connecting cable must also be compatible with the output .
• If you are using only one conventional smartphone, an output of 5.0/1A (= 5W) is sufficient (if the smartphone supports fast charging, even higher output will be effective).
• Charging devices that require a lot of power, such as tablets, requires an output of 2A (=10W).
• High-power chargers with multiple ports can quickly charge multiple devices at the same time
• Ultimately, choose the maximum output and number of output ports that match the required output of the devices you want to charge and the number of devices .

Step 2: Choose a storage method - Don't waste the electricity you generate

Weaknesses of solar chargers

Charging efficiently and in real time while outdoors, especially while hiking, is surprisingly difficult

In terms of mountain climbing in Japan, courses that are exposed to sunlight all day are not that common unless you're on the ridges of the Alps above the tree line. Even in midsummer, the weather can change quickly, with showers and other sudden showers, and it's rare for sunlight to be out for long periods of time. For devices that require a high current, such as tablets, charging may not proceed at all if the sunlight is weak

Even if charging is successful, if you have multiple devices, it is nearly impossible and inefficient to swap in the next device just as one is fully charged

Overcoming the weaknesses of solar chargers by using them in combination with batteries

To overcome these two weaknesses of instability and inefficiency, it is very effective to use a solar charger in conjunction with a storage battery. There are two ways to do this

1. Bring both a solar charger and a mobile battery

The simplest method is the one I currently use. I generate electricity using a solar charger, store it in a mobile battery connected via USB cable during the day, and then later connect the necessary devices to the mobile battery to charge. The biggest of this method is that you can choose the specifications of both the solar charger and the mobile battery that you are satisfied with, so you are likely to have the most efficient equipment. Of course, one of the key points when doing this is to choose a battery capacity that matches the device you will be charging. The downside to this method is that in most cases both the panels and batteries tend to be large, making your luggage bulky and heavy.

By the way, this type of model is available as a set of panel and battery (photo above, left), so if you choose one of those you can rest assured about compatibility

2. Choose a solar charger with a built-in battery

On the other hand, if you're interested, the ideal solution would be a solar charger that integrates the solar panel and battery. It has two advantages over separate units. First, the integrated design makes it lightweight and compact . Second, there's no need for a cable between the solar panel and battery, so there's less risk of power loss or a disconnection . In theory, it's more compact, efficient, and durable, so it seems like it has all the advantages.

However, as mentioned in the table above, I have yet to see a model of this type that offers satisfactory performance from both the solar panel and the battery, and in most cases the battery capacity is low or there is only one output port, so it is not possible to charge many devices at the same time. At present, this is only an option that I would recommend if you only have a few devices to charge, and you want to generate power in a lightweight, compact, and portable way .

Points to consider when choosing

• For more efficient power generation and charging on long trips, we recommend using a solar charger in combination with a mobile battery . However, this will increase the weight, so you should consider the number of devices and the number of days you will be traveling.
• If you prioritize compactness, we recommend a solar charger with a battery . However, the charging capacity is small, so it may not be enough if you prioritize volume, such as for long periods of time or for multiple devices.

Step 3: Choose based on ease of use - Check for ease of use outdoors -

Type and number of output port terminals

Almost all solar chargers these days have a USB output port. This is generally fine, but when it comes to outdoor devices like GPS and portable radios that use AA and AAA batteries, it may be more efficient to choose a model that has a USB output and can charge both AA and AAA batteries .

However, even if you try to keep everything as minimal as possible, digital cameras are often the only devices that require dedicated rechargeable batteries and are only powered by AC, so personally I am not yet able to dispense with all spare batteries (although if the camera has a USB port for charging, you can charge it directly from there)

Also, to digress a bit, even though some devices can be charged via USB, you should be careful as the terminals are sometimes unusually shaped. For example, as shown in the photo, many smartwatches have a USB terminal on one side, but the other has a special terminal shape, so they cannot be charged using the standard USB (A) - USB (Micro-B) type. When you go into the mountains, be sure to bring the correct charging cable for your device .

waterproof

A solar charger intended for use on sunny days may not necessarily need to be completely waterproof. However, considering that it may be used in a canoe, near water, or placed on snow, if it breaks down even when slightly wet, it is not suitable for outdoor use. When purchasing, it is reassuring to make sure that it is weather-resistant to the point that it can be used even if it gets wet as long as you wipe it off quickly

Automatic recharge function

Some solar chargers require you to replug the cable if the charging is interrupted due to a shadow or a change in the sunlight, which can be a bit worrying when you're hiking and don't want to constantly check the charging status, and the weather can be changeable

Therefore, when choosing a solar charger for outdoor use, we recommend choosing a model that has an automatic recharging function

This system has different names depending on the brand, but for example, Goal Zero calls it the auto-recharge function, RAVPOWER calls it iSmart technology, and Anker calls it powerIQ technology. If your model has this function, once you connect it, even if charging stops, it will automatically reconnect to the device to be charged when sunlight comes in again, without having to replug the cable, eliminating the hassle

Size and weight

Naturally, the lighter and more compact something is, the better, but in the case of solar chargers, the panel area and power generation efficiency are closely related, so it cannot be said that something is always better just because it is light and compact

This discussion will be based on the models we actually investigated, but models with larger surface area and weight tend to have higher output on average, and many favorable trends were observed, such as performance being less likely to decline due to slight shade or the angle of the sunlight depending on the time of day.

Of course, the ideal charger would be lightweight and compact, yet offer stable, high-output power, but at present, such a perfect model is impossible to achieve. Even if it's large, it's still slightly smaller than two sheets of B4 paper, weighing around 400-600g. If it can provide high output and stable power storage, then perhaps it's worth compromising on size and weight. Currently, if you absolutely need something lightweight and compact, you have to accept some expense and a lack of power

Depending on the type of panel, there are models that can be folded up very compactly. When considering a model, aim for one that satisfies both output and portability

Panel mounting grommets and device storage pockets

When charging while walking, the solar charger is usually placed on the front of the backpack so that it receives sunlight on your back. In this case, the panel needs to have grommets on the corners. There should be at least two on the top left and right, but for a more secure fit, having grommets on other parts will improve usability. Just to be sure, check before purchasing

It is convenient to choose a solar charger model that has at least enough grommets on both sides so that it can be hung from a backpack

When connecting and charging devices while generating power, there is a subtle but important problem of where to store the devices if the cable is not long enough to fit the device in a backpack. In such cases, it is convenient if the solar charger comes with a small pouch for storing electronic devices, allowing you to store your devices safely and easily

It's surprisingly convenient to have a portable battery in the pouch that comes with the solar charger. However, be careful not to let it fall out while you're walking

Incidentally, lithium-ion batteries used as rechargeable batteries often generate a lot of heat while charging, and if left in direct sunlight, they can become so hot that the device stops functioning (charging can stop). It is best to store the device in as cool a place as possible while charging, so for that reason, make sure to store it somewhere that is shaded from sunlight when charging

Durability of terminals and cables

The terminals that connect the solar panel to the device are very delicate, and yet many models are made carelessly. Considering the risk of the cable breaking, it's best not to have an included cable, but most models do come with one, so if that's the case, make sure to check at the end to make sure it's not in a place that's easy to bend, or that it's thin and likely to break

summary

Whether we like it or not, these electronic devices and software that improve safety and convenience have been increasing in number in recent years. Even if you think "I'm fine with it for now," your opportunities to use them will certainly increase compared to the past

Of course, it is true that none of these tools are essential for hiking in the mountains. We also do not reject the attitude of not relying on such scientific technology. However, actively utilizing these tools to make mountain climbing more comfortable and discover new enjoyment is also a part of one's style. If you are going to use them, the shortcut to safety is to choose the appropriate gear based on the correct knowledge and information. We hope that this article will be of help in that regard. Of course, when using these electronic devices, it is essential that you never rely too much on them, and that you have the skills to descend the mountain safely even if they stop working

On the other hand, the solar charger market is still immature, with many poor-quality products. There's little reliable product information, and even the manufacturers (agents) I contacted for this article gave me incorrect information (true story). Prices range from surprisingly cheap to expensive, and the prices are hard to justify, so it's hard to find a reliable product. Therefore, I'd like to share the results of my comparison and testing of models from major manufacturers in the near future, so please stay tuned