1) Module Polarity Information 

It is extremely important to recognize the correct polarity of the PowerFilm® modules!The positive end of the solar module is shown in the diagram below. A diode, such as 1N5817, is recommended to prevent the solar module from draining the battery when the solar module is in the dark. A diode is not required for a battery-free electrical device. The positive end of the module connects to the positive end of the load. The negative end of the module is also shown in the diagram and should be connected to the negative end of the load. The recommended connector wire size is a minimum size of 24 gauge. As an extra measure, connect the solar module to a digital multimeter for polarity (+,-) identification. On solar modules with copper tape leads, remove a small piece of the clear coating that is on top of the copper tape to ensure good contact between the alligator clips of the digital multimeter and the copper tape. 

Warning! Do not connect a charged battery backwards or reverse polarity to the solar module, this will destroy the solar module and may cause the battery to explode causing bodily harm, even death! 

2) Module Selection 

Select PowerFilm® modules according to:

• Operating Voltage and Operating Current Required
• Use Environment
• Specific Applications Needs

Operating Voltage and Operating Current Required
Identify the Operating Voltage and Operating Current that your system requires. For direct powering devices, calculate the requirements of the total system. 

Charging Batteries: Voltage
First, select the required Operating Voltage of the solar module for your load. As a general rule of thumb, a solar module with an Operating Voltage of 3-3.6 volts will charge 2 AA rechargeable 1.2 volt batteries. A solar module with an Operating Voltage of 7.2 volts will charge 5 AA rechargeable 1.2 volt batteries or a 6 volt gel or lead acid battery. A solar module with an Operating Voltage of 15.4 volts will charge a 12 volt gel or lead acid battery. 

DO NOT CHARGE ALKALINE BATTERIES. THEY ARE NOT RECHARGEABLE.

CONTACT YOUR BATTERY MANUFACTURER FOR CONFIRMATION THAT YOUR BATTERY IS APPROPRIATE FOR YOUR SYSTEM WITH THE SOLAR MODULE. 

Charging Batteries: Current
Second, select the appropriate Operating Current of the solar module to charge your load. As a general rule, do not charge a rechargeable battery with more current than 10% of its rated capacity. For example, a 700mA-hour battery can be safely charged with a solar module that delivers an Operating Current up to 70mA. 

Connecting Modules for Higher Operating Voltage and Current
You can parallel and series connect solar modules to achieve higher voltage (series connected) or higher current (parallel connected). However, only put like modules together: for example, two MP3-37s or two MP7.2-75s, but do not mix them. Parallel connecting two similar modules will double the output current and series connecting three identical modules will triple the output voltage. 

Warning! We do not recommend series connecting solar modules for an output voltage greater that 48V. Voltages above this can be deadly! 

The diagram below graphically demonstrates parallel and series connected solar modules: 

Use Environment
If the use environment is a permanent outdoor direct exposure environment, it is essential that the solar module system be UV-stabilized and protected from moisture. (In rare cases this may not be important if the required lifetime is less than one year.) Solar modules in the PowerFilm® WeatherPro^TM Series are specifically designed for permanent outdoor direct exposure environments. 

Other use environments are generally less demanding and do not require the added protection offered by the PowerFilm® WeatherPro^TM Series. Use environments and usage patterns vary significantly. Always test the selected solar module in its specific use environment and according to the usage pattern to confirm it meets those aspects of the specific application needs. 

Specific Application Needs
Some applications have specific needs. Examples include: ultra thin profile, specific footprint, ability to connect the solar module to the load from the back side of the module, pressure sensitive adhesive, etc. To meet specification needs we have developed several PowerFilm® Series. 

3) Series Description 

PowerFilm^® Wireless Electronics Series 

Modules in the Wireless Electronics Series offer a new opportunity to solve the old problem of limited power for wireless electronics for portable and remote applications. Wireless Electronics modules are lightweight, paper thin, and durable. Their ultra-thin profile enables them to be easily integrated with devices for solar recharging or direct powering. Modules have been specifically developed to recharge AA, AAA, and 6V and 12V batteries. These modules do not have a UV-stabilized surface. For connection, just solder or crimp to the copper tape. 

PowerFilm^® RC Aircraft Series 

The RC Aircraft Series modules are designed to be easily integrated with remote controlled Aircraft. These modules are very lightweight, can be soldered to from the back of the module via the extended copper tape, and have an extra edge seal for protection from fuel contamination and weather. Modules are available with a strong pressure sensitive adhesive for simple bonding. These modules do not have a UV-stabilized surface. For connection, just solder to the copper tape. 

PowerFilm^® WeatherPro^TM Series 

The WeatherPro^TM Series is the right choice for permanent outdoor applications that are directly exposed to the elements. The especially rugged construction of these modules includes a UV-stabilized surface, extra edge seal for weather protection, and tin-coated copper leads that extend from the module. Coating the leads with an RTV silicon compound can provide a tightly sealed package. 

4) Product Line Overview 

The PowerFilm® Product Line Overview highlights the solar modules available in each PowerFilm® Series. We strongly encourage first to try one of these standard products. If you require a custom product to meet your needs, please email FlexSolarCells.com. 

5) Wireless Electronics Series Instruction 

Leads and Testing 

The leads on the modules in the PowerFilm® Wireless Electronics Series are the copper tape strips located at each end of the solar module. Remember to check the Polarity! To test the module using alligator clips for the connection to the tester, ensure the clips make direct contact with the copper tape. The coating over the copper tape will likely need to be scraped away to ensure direct contact. 

Connecting the Module to a Load
Connection methods include soldering, crimping or using alligator clips. Remember to check the Polarity! 

Soldering 

The solar modules should be soldered to from the front. The positive copper contact is on one end and the negative is on the other end (see section on Polarity). 

Use the hot tip of the soldering iron to melt through the clear coating over the copper tape. Be careful not to burn through more than just the thin clear coating. Burning too deeply can damage the solar module. Although not necessary, it is possible to remove a small piece of the clear coating with a sharp knife prior to soldering to the copper tape. 

Good contact can be made by melting and depositing a dot of solder to the exposed copper tape.Use a low temperature soldering iron adjusted to about 600 to 650 degrees (F). It is also acceptable to solder directly to the copper tape, without using a solder dot. 

Crimping
A pressure method of mechanically securing a terminal, splice or contact to the copper strips may be used. 

Alligator Clips
Although not the most secure connection option, alligator clips may be used. 

Fastening the Module 

The modules may be fastened in several ways: Epoxy, silicon, super glue, 3M super 77 spray, double-sided acetic tape, etc. Be sure to choose adhesive based on the material to which module is being attached. Also, be careful not to get any adhesive on the front side (dark side) of the module since it will degrade overall performance. 

6) RC Aircraft Series Instruction 

Leads and Testing 

The leads on the solar modules in the PowerFilm® RC Aircraft series are the copper tape strips at each end of the module. In this series the copper tape is specially folded around the back of the solar modules so it is possible to solder to the backside of the module. Remember to check the Polarity! 

Connecting the Module to a Load
Connection methods include soldering, crimping or using alligator clips. Remember to check the Polarity! 

Soldering 

The solar modules should be soldered to from the back. The positive copper contact is on one end and the negative is on the other end (see section on Polarity). 

Use the hot tip of the soldering iron to melt through the clear coating over the copper tape. Be careful not to burn through more than just the thin clear coating. Burning too deeply can damage the solar module. Although not necessary, it is possible to remove a small piece of the clear coating with a sharp knife prior to soldering to the copper tape. 

Good contact can be made by melting and depositing a dot of solder to the exposed copper tape.Use a low temperature soldering iron adjusted to about 600 to 650 degrees (F). It is also acceptable to solder directly to the copper tape, without using a solder dot. 

Modules with Pressure Sensitive Adhesive (PSA) on the back require the release liner to be removed before the solder dot is placed. Once the solder dot is formed a wire can be attached. 

Fastening the Module 

Modules without the Pressure Sensitive Adhesive (PSA) 

A double-sided adhesive tape or spray adhesive may be used to mount the solar module. Be careful not to get spray on the front of the modules since this will degrade overall performance. 

Modules with the Pressure Sensitive Adhesive (PSA) 

The release liner on the PSA modules is clear, carefully pick at the back (silver side) corner of the module until the release liner starts to exfoliate. Once the module with PSA is mounted it cannot be removed since the PSA adhesive is permanent! 

7) WeatherPro Series Instruction 

Leads and Testing 

The leads on the PowerFilm® WeatherPro^TM Series are tin-coated copper leads extending from the module. Remember to check the Polarity! To test the module using alligator clips, ensure the clips make direct contact with the copper tape. The coating over the copper tape will likely need to be scraped away to ensure direct contact. 

Connecting the Module to a Load
Connection methods include soldering, crimping or using alligator clips. Remember to check the Polarity! 

Soldering 

In the WeatherPro^TM Series, the tin-coated copper leads extend from each end of the solar module. The positive copper contact is on one end and the negative is on the other end (see section on Polarity). 

Good contact can be made by melting and depositing a dot of solder to the exposed copper tape. Use a low temperature soldering iron adjusted to about 600 to 650 degrees (F). It is also acceptable to solder directly to the tin-coated copper leads, without using a solder dot. 

Crimping
A pressure method of mechanically securing a terminal, splice or contact to the copper strips may be used. 

Alligator Clips
Although not the most secure connection option, alligator clips may be used. 

Fastening the Module 

Adhesives will NOT work since the coating is a material from the Teflon family. You may however use a variety of mechanical fasteners including: grommets with screws or bolts, tube clamps, or framed enclosures. Use only along the weather seal (extra material around edges of solar module) and be sure to stay 1/4" away from the active aperture of the cell. 

Key Concepts

• Module current increases nearly linearly with light intensity.
• Module operating voltage is relatively insensitive to the light intensity, dropping about 5% in 10% of full sun.

Usefull Definitions

• Power point - The operating voltage and current which produce the maximum power from the module. (Forcing the module to operate at a higher or lower voltage results in a less efficient operation).
• Duty Cycle - Percentage of time that an application is expected to operate.
• AM1, AM1.5 - For all intents and purposes - Full sun illumination intensity on a clear day at noon. 
  
  

Calculations for Systems Without Batteries 

Voltage Considerations 

The voltage of the module should be selected so that the power point voltage is near the required operating voltage of the application. As a rough estimate, you can figure that the power point voltage is about 75% of the open circuit voltage. 

Current Calculations 

1. Find the minimum current needed for the application: I_min 

2. Determine the minimum light intensity (threshold intensity) under which the application will run: L_min (The table below gives a rough idea of light intensity under various conditions. Intensity is rated as a percentage of full sun intensity (also called AM1.5) 

3. Calculate the required full sun current specification for your module: I_mod 

I_mod = I_min x 100% / L_min

4. Chose a module that matches the voltage required and the current, I_mod calculated. 

Note: Module performance is usually specified in terms of current @ a specific voltage (i.e. 50mA@3V) which gives performance at a specific operating point. This operating point is usually close to the power point. Some modules are specified at full sun and others at lower intensities such as 1/4 Sun. This is done to simplify selection. 1/4 sun is a more typical intensity used by portable electronics and is often chosen as the threshold intensity. 

Example Calculations for Applications using Direct Power 

Example 1: A radio to be powered by the module requires 9 mA at 3 Volts to operate. You want the radio to operate with any illumination above 20% of full sun. 

I_mod = I_min x 100% / L_min

I_mod = 9mA x 100% / 20%

I_mod = 45mA

You need a module which will produce 45mA @ 3V under full sun illumination. 

Example 2: Same as Example 1, but the given operating light is office light. L_min = 0.4%. 

I_mod = I_min x 100% / L_min

I_mod = 9mA x 100% / 0.4%

I_mod = 2250mA

You need a module which will produce 2250mA @ 3V under full sun illumination. This is a very large module for a radio. A better solution may be to use a smaller module coupled with a battery which recharges from the module when left in a window. 

Example 3: You want a flashing LED for a point of purchase display which works under store illumination. The flasher circuit uses an average of 0.1mA at 2.4 Volts to power 5 LEDs. From the chart above we see that store lighting gives L_min = 1.3% 

I_mod = I_min x 100% / L_min

I_mod = 0.1mA x 100% / 1.3%

I_mod = 7.7mA

You need a module which will produce 7.7mA @ 2.4V under full sun illumination.Alternatively, you might look at the low-light specifications where performance is given at 0.4% of full sun (about 400 Lux). This can be normalized to the 1.3% level. 

Calculations for Systems with Batteries 

Voltage Considerations 

For battery charging applications, the operating voltage of the module should be at least as high as the charging voltage of the battery. This is higher than the battery's output voltage. A single NiCd battery has a typical output voltage of 1.2 volts, but requires 1.4 Volts for charging purposes. A 12 Volt lead acid battery needs a charging voltage from 14 to 15 Volts. In cases where a blocking diode is required to prevent the battery from discharging through the solar module when the module is in the dark, an additional 0.6 V is required. As an example, a battery pack with 3 NiCd batteries, which operates at 3.6 Volts, needs a module with either 4.2 or 4.8 V depending on whether a blocking diode is used. 

Is a blocking diode required? 

When the solar module is in the dark and still connected to the battery, it is simply a forward biased diode and can drain current from the battery. This is less of a problem for amorphous silicon modules than single crystalline modules, but can still be a problem if the module is in the dark a large percentage of the time. The leakage rate also drops dramatically if the open circuit voltage of the module is significantly larger than the output voltage of the battery. For applications that get sun daily, diodes can probably be ignored if the module is sized correctly. If the application is going to spend extended time in a case or drawer, however, a blocking diode would be advisable. Each application should be evaluated individually for this choice. 

Current Calculations 

Example Calculations for Applications with Batteries 

Example 1: A yard light draws 20mA and you want it to work for 8 hours per night. You estimate that you get the equivalent of 4 hours of full sun per day. 

I_avg = I_app x duty cycle 

I_avg = 20mA x 8hr / 24hr

I_avg = 6.67mA

L_avg = 100% x 4hr/24hr

L_avg = 16.67%

I_mod = I_avg x 100% / L_avg

I_mod = 6.67mA x 100% / 16.67%

I_mod = 40mA

Example 2: A mobile phone draws 3mA in standby mode and 300mA in talk mode. It is assumed that the phone is used in the talk mode for an average of 10 minutes per day, while in the standby mode for 23hrs and 50 minutes. The phone can get an equivalent of 2 hours of direct sunlight per day. Find the module size needed to keep the phone charged. 

I_avg = I_app x duty cycle 

I_avg = {3mA x [(23hr 50 min)/24hr]} + [300mA x (10min/24hr)]

I_avg = {3mA x [(23hr x 60min) + 50 min]/(24hr x 60min)] + {300mA x [10min / (24hr x 60min)]}

I_avg = [3mA x .993] + [300mA x .0069]

I_avg = 5.05mA

L_avg = 100% x 2hr/24hr

L_avg = 8.33%

I_mod = I_avg x 100% / L_avg

I_mod = 5.05mA x 100% / 8.33%

I_mod = 60mA

If the charging voltage of the phone is 6V, you will need a 6V, 60mA module at the very least to supply all needed power from the module. 

Example 3: A fishing boat has a 12 volt battery system which powers a trolling motor and depth finding equipment. The boat is in use 4 days out of every month and requires an average of 2A for 6hrs of use per day. The boat will get an average of 4.5hrs of sunlight per day. Calculate the module size needed considering a monthly cycle. 

I_avg = I_app x duty cycle 

I_avg = 2A x [(4 x 6hr)/30 days]

I_avg = (2A x 1000mA/1A) x (24hr / 720hr)

I_avg = 2,000mA x 0.0315

I_avg = 63mA

L_avg = 100% x 4.5hr/24hr

L_avg = 18.75%

I_mod = I_avg x 100% / L_avg

I_mod = 63mA x 100% / 18.75%

I_mod = 336mA

If the boat is used 4 days per month with the days separated by equal time intervals, a 14V 400mA module should be sufficient to store enough energy to run the boat. However, if the boat were used 2 consecutive days, there would not be enough time to fully recharge the battery before the next day's use. If the capacity of the battery is sufficient, this will not be a problem, but if the capacity of the battery is such that only one day's energy can be stored in it, more charging capacity will be needed and the calculations will have to be redone on a daily cycle.