How to find the right solar generator

Various types of lithium solar panel cells are currently used in solar generators, which can be roughly divided into two groups based on their cell voltage. In the case of Li-ion batteries, the positive pole consists of various but similar lithium compounds with a cell voltage of 3.6 volts to 3.7 volts. They have a high energy density of 150 Wh/kg to 260 Wh/kg. For the most part, however, they only last between 500 and 2,000 complete charge cycles before their storage capacity has fallen to 80 percent of the nominal value.

In lithium iron phosphate batteries, LiFePO4 for short or LFP for short, the cell voltage is slightly lower, between 3.2 volts and 3.3 volts. Their energy content is lower at 90 Wh/kg to 120 Wh/kg, but they can be fully charged 3,000 times or more before they drop to 80 percent. If mobility is your most important criterion, Li-ion batteries are the first choice. If the solar generator is to be used primarily as a buffer store, it is better to use LFP technology. Due to their lower energy density, LFP batteries are theoretically a little safer, but in practice the quality of the design and workmanship of the power station is of crucial importance.

First determine the need

Before you buy a solar generator, you should think about its use and your energy requirements. If weak consumers such as USB devices or even a laptop power supply unit are primarily supplied with energy, a compact and still portable solar generator of up to around 500 Wh is usually sufficient. It usually offers an AC output, a 12 V -Car socket, several USB-A and possibly also a USB-C socket. For the latter, pay attention to the output power. If you want to use it to charge a notebook, this output should be able to deliver at least 60 watts.

If you want to connect several AC devices to the solar generator, it is advisable to take stock of the energy required. With an inexpensive energy meter you can quickly get an overview. With large consumers, such as hedge trimmers or even a kettle, you must also take the inrush current into account. It is therefore not enough to just pay attention to the capacity of the power station. Equally important is the power that each AC socket can be loaded with – both in continuous operation and as a short-term inrush load. A 5000 watt solar generator may be your best choice for home backup power. The inverter itself also requires energy. As a rule of thumb, you have to calculate around 15 percent of the total capacity as a loss under continuous load. Therefore, at least the AC sockets should be able to be switched off.

As a rule, the solar generators do not emit a warning sound when their capacity is exhausted. If you use it to supply energy-critical devices such as a refrigerator, you should check the status on the display or in the app from time to time. In the event of an overload, there is also no warning, but the relevant output is simply switched off.

Heat is generated wherever energy is converted. At the latest from 30 watts, the fan switches on with most solar generators. You should keep this in mind when setting up the power station next to your tent on the crowded campsite at night.

Pack the sun in the tank

As a rule, solar generators can be charged in three ways: with alternating current via an internal or power supply unit and with direct current from the solar panel or the 12 V or 24 V vehicle electrical system. The necessary charging time results from the capacity of the solar generator divided by the power of the selected input. There are serious differences when charging, especially via the AC input. If the power station can be charged quickly, it can be filled in a few hours, otherwise it can take half a day. Some devices also show the remaining charging time in their status display.

At the solar entrance, in addition to the efficiency and performance of the solar battery, the angle of incidence of the sun and the cloudiness in the sky are the decisive factors. Clouds in front of the sun quickly reduce performance by a factor of ten. With changing solar radiation and temperature, the operating point of the solar panel changes constantly. For an optimal yield, the power station should therefore have an MPPT function. With this “Maximum Power Point Tracking”, the “maximum power point search”, the load on the panel is constantly trimmed to optimal power output. The more area the panel has, the more powerful it is, but it also becomes more unwieldy as a result. For mobile use, a foldable 100-watt solar panel is a manageable compromise.

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For all the power stations presented here, there are also suitable solar panels in various power levels from the same manufacturers. Usually even in a cheap bundle. With such a kit you don’t have to worry about the right connection. Unfortunately, there is no uniform plug standard for this. In practice, however, two connection types are particularly widespread: either the power station has a separate two-pin XT90 socket, the shape of which is familiar from model making, or the panel is plugged into the same DC input instead of the power supply unit. Appropriate adapters are usually included. Therefore, if you prefer the solar panel from another manufacturer, clarify the connection options beforehand. When choosing a panel, don’t just compare the prices, but also the efficiencies of the solar cells you are considering.