Nikkei Electronics Teardown Squad started to examine the performance of the solar cell module, which is mounted on the rear chassis of the Solar Phone SH002 as its main feature.
According to KDDI, when charged for about 10 minutes in fine weather, the mobile phone provides approximately one minute of voice call or two hours of standby time (See related article). Therefore, we charged the handset by using the solar cell module before disassembling it.
We began charging the battery at noon June 7, 2009. Though some clouds were seen in the sky, it was nice and fine.
As for the evaluation method for the solar cell module, the SH002 has a function to show information on the status of charging on its 1.1-inch black-and-white electronic paper mounted on the rear chassis. When the module is being used, its charging efficiency is shown in four levels, "optimal charging," "charging," "charging stopped" and "solar power unavailable."
When the power is off, the SH002 indicates an estimate of available talk time up to five minutes. So, we started charging the battery when the remaining battery power was zero and stopped it when an icon appeared to indicate that five-minute or more talk time is available. And we measured the time it took.
First, we exposed the handset to sunlight. Because it was a sunny day, the icon of "optimal charging" was shown on the electronic paper. On the seal attached to the solar cell module, there were messages such as "Do not leave it in high-temperature places like in a car. It could lead to heat generation, ignition, deformation and breakdown."
Though we believe that the layout was sufficient for the experiment, it might not meet recommended conditions. In fact, when the angle of the module to the sun was changed, the icons of "charging" and "solar power unavailable" appeared.
In the experiment, the icon indicating one-minute talk time was not displayed even after 10 minutes of charging. In the end, it took about 40 minutes for one-minute talk time, 60 minutes for three-minute talk time and 85 minutes for five-minute talk time.
In other words, to have talk time of one minute, it took several times longer than 10 minutes, the charging time Sharp announced. Considering the light intensity and the angle to the sun, the results might be reasonable. In fact, KDDI and Sharp define the solar cell module as an auxiliary power source. The module will be useful when it is not possible to use an AC adapter to charge the handset, for example, outdoors.
We finished checking the charging function of the solar cell module and started to tear down the chassis.