Introduction
Inhaltsverzeichnis
Performance capacity 5 volt output
The SolarStrap is capable of charging up any gadget that is charged by a standard USB plug. According to the manufacturer the internal battery has 1500 mA, which equates to a capacity of 5.55 watt-hours. However, since the voltage needs to be converted to 5 volts, there is a power loss. In our test we measured an obtainable capacity of 4.00 watt-hours with a load of 2 watts and an average voltage of 4.8 volts. In consideration of its little weight, this result is even in comparison to external batteries without solar function a good value: see comparative test about external batteries below 100 g.
The maximum output given by the manufacturer is 1000 mA. In our test this value was achieved smoothly. The maximum output could be determined/recorded with about 5 watts. Thus the SolarStrap is capable of charging up even an iPad1 to approximately 15%.
Solar power
Our test conditions in detail:
- Discharging SolarStrap
- 2 hours charging at orientation to the midday sun, cloudless sky, 20 ° C
- Discharging SolarStrap and measuring the watt hours: 0.41 Wh
- Surface of the solar panel: 48 cm2
- Assumed solar radiation with 0.1 watts per cm2
- System efficiency of 4.3 %
A very good value for such a compact system!
Concerning an iPhone 3G, the manufacturer Suntrica gives the following information:
| Solar charging at optimal conditions | Talk time |
Standby time |
| 2 hours | 40 minutes | 16 hours |
| 4 hours | 1.2 hours | 32 hours |
| 8 hours | 2.5 hours | 64 hours |
In two hours we harvested 0.41 watt hours. To be able to compare the manufacturers product information with our measured value, we have calculated as follows:
- iPhone 3G battery capacity is 4.2 watt hours
- iPhone 3G standby time is specified with a maximum of 300 hours
- iPhone 3G standby consumption thus 0.014 Wh per hour
- thus, 16 hours correspond to 0.224 watt hours
Our test result is therefore well above the manufacturers data. However, one must take into account the charge efficiency of the iPhone and even the standby time of 300 hours proved to be very optimistic of Apple. Conclusion: the manufacturers data are serious and correspond at the very least to the output of the SolarStrap!
Attaching the SolarStrap to a backpack or strapping it more or less vertically to the body (as recommended by the manufacturer), is hardly loaded effectively. In an 8-hour day trip in perfect weather through forest and meadow (50/50) at the end of the day we could reach only 0.32 watt hours. As with all solar applications, the durable, shadow-free and good exposure to the sun is vital! In practice and being in action one should therefore have realistic expectations towards the small device!
Conclusion
The SolarStrap Universal is a high quality, small (65 g) but powerful (5 watts) solar charger with a built-in rechargeable battery (4 watt hours). The design is very solid, the workmanship is of high quality, splash proof, shock resistant and therefore fully suitable for outdoor use.
We were able to confirm the manufacturers claims regarding the loading capacity of the solar panel which is, in view of the small size of the modules, very good. In practice, however, one should adapt ones expectations to the size of the device. Only by optimal and unshaded alignment a charging power of 0.2 watts is reached. Furthermore, the price of 59.99 EUR is in our opinion a bit too high. Apart from that our product review is: highly recommended!
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