Solar Cells Info

Nikkei Electronics Teardown Squad, Jun 24, 2009
Source. TechOn
http://techon.nikkeibp.co.jp/english/NEWS_EN/20090619/171931/

An environmentally-friendly mobile phone debuted in Japan, which is now enjoying an “eco boom.” It is Sharp Corp’s “Solar Phone SH002” released by KDDI Corp as one of its summer 2009 models of the au brand mobile phones.  The SH002 is equipped with a solar cell module on the back of its chassis. The solar cell module can be used as an auxiliary power source when the remaining battery level is low or zero. Though Samsung Electronics Co Ltd and LG Electronics Inc announced handsets with similar concepts at Mobile World Congress 2009, which took place in February 2009, Sharp is the first company that released such a product in Japan.

According to KDDI, the official release date of the SH002 is June 4, 2009, but the date differs depending on region. Just in case, we checked with the nearest outlet store for au handsets and received an answer that the SH002 will be launched in Tokyo on June 5 but only nine units (three units for each of three colors) will be available at the shop.

Therefore, we waited in line at the shop before hours on the release date and purchased the SH002. We obtained it not for personal use, of course, but for reporting the usability and the mounting technology used for the solar cell module to our readers.

To start with, we took out the handset to actually use it. 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.

[Part 3]
In the previous article, we checked the usability of the solar cell module equipped in the Solar Phone SH002, which KDDI released as one of its summer 2009 models of the au brand mobile phones. Then, we moved on to break down the display unit incorporating the solar cell module.  The SH002 features waterproof property that complies with IPX5/IPX7 standards. Therefore, we expected that it would be more difficult to disassemble the handset compared with other mobile phones.  The display unit is composed without screws, and its cover is attached by using double-faced tape. We inserted a flat-blade screwdriver between the chassis and the cover to remove the cover and check the solar cell module.

Next, we began to take out the solar cell module, which was fixed on the frame together with 1.1-inch black-and-white electronic paper. On the back of the module, there were electrodes probably for grounding, and they were connected to metal part on the back side of the frame. The module might produce electromagnetic noise.
The solar cell module and the 1.1-inch electronic paper are fixed on the frame. We could not determine the manufacturer of the electronic paper.

Furthermore, we took out the solar cell module from the frame. The module measures 67.5 x 41.0 x 0.8mm and weighs about 4g. Its back is printed with two marks, “Sharp” (manufacturer) and “LR0GC01” (model number). The LR0GC01 has the same dimensions as the “LR0GC02,” the solar cell module that Sharp announced for mobile phones in May 2009 (See related article).

“The LR0GC02 has almost the same specifications as the LR0GC01, but it’s a different model,” the company said. “Also, it is possible to change the electrode pattern on the surface of the module.”  The chassis and the cover on the side of the LCD panel were firmly attached to each other with double-faced tape. In general, there are two methods to realize waterproof property. One is double-faced tape, and the other is waterproof gaskets.  “Double-faced tape ensures a high waterproof property but makes it difficult to rework the internal design in the case of an accident,” said an engineer from a Japanese handset manufacturer.