Brian Chapaitis
Summer Institute of Linguistics
Papua New Guinea Branch
March 2010

For the first time in recent memory, advances in solar technology and computer laptop technology have converged such that the goal of language work performed by PNG Mother Tongue Language Workers (MTLW) can be realized in a relatively cost-effective manner by themselves and for themselves - with minimal oversight. This paper primarily concerns itself with hardware issues, while briefly mentioning useful language software tools under development by SIL and other agencies. It does not address national training issues. It is meant as a “handbook” or a guide to collect in one place all the relevant technical issues and potential hardware suppliers useful to SIL administrators who want to set up unassisted, long term, national coworker projects with minimal mentor contact. In short, it is an effort to outline the application of technologies for a sustainable MTLW programme and represents the present “state of the art.”. This is a constantly moving target since technology changes so rapidly. Be sure to read the latest version available of this document.

Picture: Dominic Pusai (Goiniri language) helps Joseph Aputa (Barupu language) as Joe checks out the team's first Asus Eee 1101HA netbook computer. Physically smaller than the translators' old Toshiba laptops (see inset), netbooks typically use only about 1/3 the power, making our solar-charged batteries last far longer. Aitape West Multi-Language translation project, north coast, Papua New Guinea (11 languages in progress).

In year 2009, during a time of world-wide financial recession, the netbook was born. The marketplace literally exploded with small form-factor “netbooks” that weighed around 1.5 kilos, and cost US$ 300-400. And the marketplace responded to these inexpensive devices. Intel reports record revenues by 4Q, 2009 by the use of their ATOM processor line. Along with relative inexpensive prices, business and private users alike also discovered the wonder of “all day” computing. The ATOM processor line also represents a big break-through in the concept that “low power consumption” might be a highly desirable feature, if one can work at a coffee shop and do all day computing tasks without plugging into mains power outlets. These were simple tasks, to be sure, like Word Processing and eMail and Web Browsing. But isn't that enough?

At the same time huge advances occurred in new thin-film and poly-crystalline solar technologies within the same year. This produced the first commercial grade solar panels that were beginning to approach the US$ 3 per watt level (as compared to $8 per watt before). These light-weight panels got a tremendous boost by the OLPC (One Laptop Per Child) movement when a major supplier produced small 10 watt panels for approximately $26 each. Combined with the extreme low power of the first generation XO machines, one began so see the realized potential or “low power consuming” netbooks powered by inexpensive solar as a new frontier in our work.

This paper represents the state of the art for SIL considering the merging of these two powerful trends in the industry for new Third-World applications. We are actively developing significant “laymen” tools that, once placed on sustainable hardware, would empower national citizens to consider doing portions of the language development task. And this includes, the Bible Translation task.

“Define a complete system of hardware, a tool, suitable for third-world national coworkers to consider doing language development work for themselves and by themselves. To build reliable, self-contained, and low maintenance hardware systems, where there is no readily available mains power.”

“SCOS defines a sustainable platform by which suitable national language tools can be implemented by laymen in the field”

                          — Brian Chapaitis 

Beyond the scope of this “handbook” is the requirement of suitable national training programmes for a successful implementation within a Branch or Entity of our organization. That exercise is the subject of another paper and also would be integral to a far larger, comprehensive Branch Strategy plan.

For those who want to read the main points (and not the reasons why):

• Best Netbook: Asus 1101HA or present equivalent
• Best Solar Controller: Xantrex Model C-12
• Best Low Voltage Cutoff Setting: 12.5 volts measured at the battery terminals (not the solar controller)
• Best style of Battery: AGM
• Best Gauge Wire: 10 gauge or larger (smaller gauge number)
• Good Battery Lifetime in Use: 3 years (plan now on replacement cycle)
• Best Solar Panel: CIGS (expensive); Thin Film (inexpensive)

Note: Although the manufacturers of the solar controllers below say the order of connection of parts does not matter - the general wisdom says that under full sunlight, the converted energy of the sun's radiation should have a good place to go. Therefore always connect the battery first, or disconnect the battery last during assembly of the parts.

A flat device, sometimes called a photo-voltaic panel that converts incident solar radiation into electrical energy. Manufacturers include Gold Peak (GP) and Global Solar (GS) mentioned in this paper.

Due to rapid changes in solar radiation possible, the solar panel voltages fluctuate dramatically. The purpose of the controller is to condition the power coming from the solar panel and make this power acceptable for lead-acid battery chemistries to store electrical power, and without premature damage to the batteries, shortening their useful life.

An electro-chemical energy storage device. Many battery chemistries exist including Lithium Ion used in mobile phones, and laptops and Nickel-Metal Hydride, often used in laptops and LED flashlights. All can be re-charged. Lead-Acid is a relatively old technology, and well understood. It is favored in solar applications primarily due to relatively low cost, compared with the other, newer technologies.

A circuit component, that is designed to break, or burn, when a relatively high current is applied and thus save further damage from equipment attached to a power source. Examples are an automotive in-line fuse (which must be replaced when used once) and a mechanical circuit breaker which can be reset by the user.

Actually a voltage conditioner and regulator, netbooks would normally use these to condition the transients found in automotive 12 volt electrical systems, saving the netbook power supply from undue stress. In solar netbook applications these devices protect the netbook input power supply from voltage swings present from the solar controller charging the battery. These range from 10-14.5 volts DC, where the given netbook wants a steady 12.3 volts or 19.5 volts supplied at all times. These adapters are very energy efficient and superior to use over an AC inverter.

A new class of notebook computer that can run a major Operating System like Linux or Windows. These range in size from the early Asus 701 series at 7 inches wide all the way to the Asus 1201HA which is 12 inches wide. 10 inch netbooks are large enough for many to touch type easily on their keyboards. 11 inch is about optimal. Popular makes of netbooks come from Asus, Acer, Dell, Toshiba, Lenovo, Samsung, MSI and others. Asus is considered the most reliable by far, only to be rivaled by Apple Computer.¹⁾)

Briefly mentioned here, but designed with national lay-workers in mind, these would include the OS environment called BaLSA, and applications like WeSay, BibleEdit, Paratext, any Word Processor, eMail, and a suitable as-yet-unspecified national Literacy tool.

The maximum energy we could ever expect from average solar radiation to the ground (or insolation) would be around 1,000 Watts/m² on the earth's surface perpendicular to the Sun's rays at sea level on a clear day. But of course that would be in the ideal since there are many other factors involved where one is located. Insolation from the words incident solar radiation. Is often expressed regionally on maps as kilowatt-hours per square meter per day (kW·h/(m²·day)).²⁾ Look for insolation maps for your region which can be quite helpful for planning purposes. Obviously this has a bearing on photovoltaic (PV) or “solar” panels, but solar panels are never 100% efficient.

Monocrystalline technology. The highest efficiency ratings have been achieved on monocrystalline silicon cells (c-Si) which are very expensive to produce since one must grow silicon crystals in cylindrical “boules” and sliced into thin wafers. Hence such panels made from such cells often have an array of circular cells mounted on a substrate. The highest recorded commercial efficiency appears to be 22%

Thin Film technologies can sometimes reach 18% and “multiple junctions” higher than that. Most of the commercial production of thin film solar is based upon another compound CdTe with an efficiency of 11%. These are of interest today because of greatly reduced manufacturing costs, and you notice their rectangular nature when placed on a substrate of some kind, or perhaps a flexible roll.

“The selected materials [of thin film] are all strong light absorbers and only need to be about 1 micron thick, so materials costs are significantly reduced. The most common materials are amorphous silicon (a-Si, still silicon, but in a different form), or the polycrystalline materials: cadmium telluride (CdTe) and copper indium (gallium) diselenide (CIS or CIGS).

Each of these three is amenable to large area deposition (on to substrates of about 1 meter dimensions) and hence high volume manufacturing. The thin film semiconductor layers are deposited on to either coated glass or stainless steel sheet.”³⁾

While building a partnership relationship with the OLPC (One Laptop Per Child) group here in the Pacific we asked for their source for those flexible substrate, Gold Peak (GP) solar panels they re-sell at US$ 3 per watt. An astoundingly low price, or at least was astounding in the first quarter of 2009. The year 2010 is another matter.

Nonetheless, we have managed to get a few custom GP 20 watt solar panels made for us, and shipped to Papua New Guinea for solar experiments. At present a 20 watt GP solar panel will cost approximately US$ 75 landed in our country. You will need two panels for present netbooks, however, one will power the upcoming “smartbooks” and the newly announced Apple iPAD “tablet” style computer if you can make that kind of computer work for you.

Wondrously light weight (2.5 lbs), these panels are very easy to ship by small aircraft (20½ W x 30¼ L x 1/16 inches). They have grommet holes suitable for permanent mounts, but some are considering raising and lowering these during the day via ropes to increase security from theft.

Best of all, these panels have great “low light” or shade performance. It is not uncommon to be generating a suitable charge for the solar controllers even when skies are completely overcast.

Another promising technology are the new CIGS panels, or Copper Indium Gallium diSelenide technology. This is considered in the class of “poly-crystalline thin film”.

We have been experimenting with the Global Solar 30 watt panel model GSE-30 shown here in our latest netbook experiments.⁴⁾ The MPP (Maximum Power Point) appears to be 1.7 A at 17.5 volts, and the unit weighs 11 lbs. Dimensions 25 x 25 x 1.3 inches

This panel is relatively heavy, but ruggedly built and the active elements appear to be mounted behind glass, and within a solid aluminum frame. Designed specifically for “off grid” use, these panels are designed for high reliability in very rural applications. Just what we would want. The cost is normal however at US$ 184.00 or approximately US$ 6 per watt.

We have found these panels to be excellent “low light” performers as well. A working Asus 1101HA netbook with solar charge controller can be sustained in “overcast” conditions, and leave a small trickle charge for the AGM lead-acid battery. The netbook is fully charged, and connected to the solar panel, in this scenario, and only consuming 0.8 amps, while doing useful work.

It might be helpful to note here, that while charging a typical netbook's internal batteries, that this appears to be a most power inefficient mode. Charging currents go quite high, up to 2.4 amps at times, and somehow the energy conversion efficiency drops dramatically. If this scenario of charging/ recharging the netbook's internal batteries is required for daily use in the language program, then one would suggest larger or more solar panels than 30 watts.

Also we have now seen village allocations where the gauge of wire used from the roof top to the solar controller within the village house is way too “high” or “too small” in diameter. The user should start by thinking about 10 gauge wire as a minimum and definitely move to 8 gauge wire if available and affordable. Otherwise considerable power is wasted due to resistive losses in the length of wire required, typically 5-10 meters.

The reason for the solar controller is to condition the power from the solar panels (sometimes called a Photo Voltaic (PV) Panel) to be acceptable for lead-acid batteries. All solar panels have a Maximum Power Point (MPP) and manufacturers proudly give specifications for this. It's the “knee in the power curve” where the total power is maximized at a certain specific voltage and certain specific current output in brilliant sunshine. This point changes with the different solar panel technologies. The Morningstar and the Xantrex controllers discussed here are trying to hold the solar panels at that optimum point for max power, and also regulate the charge current for what the lead-acid battery really needs at the moment. The state of the battery is changing as it charges back up again, while the incident solar radiation is changing by the minute as well. Finally the netbook or “load” may or may not be in use. The controller then makes new and different decisions about the charge voltage and current applied. All this to help your battery live a much longer and healthier life before replacement while performing its work function as well.

The Low Voltage Disconnect (LVD) should be set in a manner that protects the netbook user from overusing the battery and potentially discharging the battery too far for a given daily charge/ recharge solar cycle. Equally important is the Low Voltage Reconnect (LVR) setting. Once the load is disconnected with a hard-worked battery, the user must be “blocked” from continuing to drain the lead-acid battery, until a suitable battery state is reached. We are suggesting here just below the standard “float” voltage or 13.6 volts, although the “Bulk” charge phase of the Xantex controller goes beyond this to 14.6 volts. Above the LVR point, the user could start working again or at least start charging the netbook's internal battery through the auto-adapter. See next section “Typical Charging Cycles”. Some consultants might consider a higher LVR setting. Obviously the user can still run, sometimes as long as 8 working hours, on the internal Li-Ion batteries of the netbook.

A very popular solar controller, and sold on many solar oriented web sites and stores. This is a sealed “potted” module with mounting brackets and terminal posts, making repair service a bit more difficult. JAARS Inc. also has these for sale at approximately US$ 50. Some very nice features are the smaller size and a solid “low voltage disconnect”, but unfortunately the built-in LVD setting at under 12.0 volts, is way too low for our purposes. See the section: “Lead-Acid Battery Life Issues” following. Because the cost of the batteries can easily exceed US$ 50 to replace, the Xantrex controller is favored. Never purchase the Morningstar SS-10 model as that does not do any LVD function at all.

However, there is a possible reason for the lower than expected LVD of the Morningstar Controller. In field testing many users are not using a proper gauge of wire, running from roof-top to controller, and especially from controller to battery. There can be a significant difference between the recorded voltage at the battery terminals and what is “sensed” by the controller, even for short wire run lengths. So for a desired LVD of 12.3 volts at the battery, the controller might have to wait for 12.0 volts at its terminals. This might explain the thinking of Morningstar, however their design is a compromise of possible conditions at best.

It might be possible that with experimentation we can alter the Morningstar LVD to be more usable, but this research has not happened to date by adding an appropriate external circuit.

Also, there is research in a “battery eliminator” circuit (removing the necessity for the Lead-Acid battery altogether) which for some field settings may be adequate. Obviously such users could no longer work in the evenings, nor run village house lights… however a system that used the Morningstar Controller that easily maintained the netbook's internal 8 hours lithium ion battery during the days with adequate sunshine,, would obviously reduce total system cost by well under US$ 150 from the total cost of the system. That might be worth the effort and the change of work life-style for the project. This also removes one extra maintenance concern (external battery) plus a prime object of theft in the village.

With a much larger physical dimensions (16.5 x 11 x 4 cm)⁵⁾) and a discrete circuit board with easily serviceable electronic parts⁶⁾) - the more expensive Xantrex C-12 controller (approx US$ 100) has significant advantages in ease of service, should something fail in the system. However one of its greatest and most desirable features is a programmable LVD cut-out of the netbook “load” when the operating voltage of the AGM battery falls below a user setting. This means that we can set the LVD to anything we want, and would suggest no lower than 12.5 volts as the maximum “depth of discharge” point. 12.6 volts would be much better. See section: “Lead-Acid Battery Life Issues” for more details on this issue. Note in the drawing (right), the five user setting controls, specifically the Low Voltage Disconnect and the Low Voltage Re-Connect. Best of all, the control knobs themselves can be removed to further discourage changes later.

Convenient Digital Voltmeter (DVM) probe points are provided to make accurate threshold settings.

Unlike the Morningstar Controller, it is now possible to compensate for field conditions. In reality, many users are not using a proper gauge wire, running from roof-top to controller, and especially from controller to battery. There can be a significant difference between the recorded voltage at the battery terminals and what is “sensed” by the controller, even for short wire run lengths. As high as 3 tenths of a volt. So for a desired LVD of 12.5 volts at the battery, the controller might have to wait for 12.2 volts at its terminals. Finally, we can accurately set the solar controller to maximize run times for the netbook, while at the same time, using the minimum Depth of Discharge (DoD see section below) to greatly extend useful life of the relatively expensive batteries. Once proper settings are established by an expert (consultant), the control knobs can be removed and front panel sealed, reducing “tinkering” later.

The Xantrex solar charge controller, like the older Trace Inverter chargers, follow a typical three phase charging method in three distinct phases: “Bulk, Absorption, Float”. The battery voltage will vary during the three stage charging process, as follows:

• BULK— The first stage of 3-stage battery charging. During this stage the PV (solar) array is allowed to charge at its full output. Once the voltage of the battery reaches the BULK voltage setting, the controller goes to the next stage. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no “correct” voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.
• ABSORPTION— The 2nd stage of 3-stage battery charging. During this stage the voltage of the battery is held at the BULK voltage setting until a timer accumulates 1 hour (C-12). Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts.
• FLOAT— The 3rd stage of 3-stage battery charging. During this stage the voltage of the battery is held at the FLOAT voltage setting. Full current from the PV array can still be delivered to the loads during this stage during the day powering the netbook. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging.⁷⁾

Both controllers here use PWM, or “pulse width modulation” where the controller or charger senses tiny voltage drops in the battery and sends very short charging cycles (pulses) to the battery. This may occur several hundred times per minute. It is called “pulse width” because the width of the pulses may vary from a few microseconds to several seconds.

If the voltage of the battery drops below the FLOAT setting for a cumulative period of one hour, a new BULK or ABSORPTION cycle will be triggered (C-12). This typically occurs during each night. If the battery is full at the start of the day, it will receive only an ABSORPTION charge for 1 hour and then be held at the FLOAT setting for the remaining period of the day unless the battery is discharged.⁸⁾ Note that the voltage levels of both the Bulk Mode and the Float mode are settings one can control, unlike with the less expensive Morningstar SS-10L model.

There are many different chemistries and construction types for lead-acid batteries. For the best information on your particular battery, please consult the manual from your particular manufacturer. Be particularly careful with Gel Cell models, since they have the largest variance from “normal” and are often abused, fail, overheat or worse, if not charged properly.

Sadly the chart on the right doesn't included “flooded lead acid” batteries, or the kind one typically finds in automobiles that need refills with distilled water from time to time. As of this writing, we are not sure what the correct charge voltages are for such a battery. See chart at right.⁹⁾ (Sb= Antimony; Ca= Calcium)

It is our opinion that SLA AGM batteries should not be equalized which means you should turn off the “auto-equalize” function on the Xantrex C-12 controller if you are using that style of battery. See “Battery Technologies” section.

A newer type of sealed battery uses “Absorbed Glass Mats”, or AGM between the plates. This is a very fine glass mat composed of Boron-Silicate fiber. These type of batteries have all the advantages of gelled, but can take much more abuse. Panasonic, Lifeline, PowerSonic, Yuasa and all the rest manufacture AGM batteries. These are also called “starved electrolyte”, as the mat is about 95% saturated rather than fully soaked. That also means that they will not leak acid even if broken - very important to the aviation industry, and therefore considered “non-hazardous” cargo. Therefore they are more easily transported.

AGM batteries have several advantages over both gelled and flooded (liquid filled), and were more expensive than gelled in the past. But recently prices have fallen such that now they are completely replacing gelled altogether, and rapidly closing in on “flooded” batteries.

Since all the electrolyte (acid) is contained in the glass mats, they cannot spill, even if broken. This also means that since they are non-hazardous, the shipping costs are lower. In addition, since there is no liquid to freeze and expand, they are practically immune from freezing damage, which is admittedly more important in northern Canada, not sub-Sahara Africa.

Nearly all AGM batteries are “recombinant” - that is - the Oxygen and Hydrogen recombine INSIDE the battery. These use gas phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis. The recombining is typically 99+% efficient, so almost no water is lost.

The charging voltage profiles are the same as for any standard battery - no need for any special adjustments or problems with incompatible chargers or charge controls as with the older Gel Cell type batteries. And, since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents. Amazingly the AGM batteries have no charge or discharge current limits (not sure that one should test this however).

AGM's have a very low self-discharge rates - from 1% to 3% per month is usual. This means that they can sit in storage for much longer periods without charging than standard batteries. AGM batteries can be almost fully recharged (95% or better) even after 30 days of being totally discharged (but please don't do this, nonetheless, as discussed more fully in this paper).

AGM's do not have any liquid to spill, and even under severe overcharge conditions hydrogen emission is far below the 4% max specified for aircraft and enclosed spaces. The plates in AGM's are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery.

Even with all the advantages listed above, there is still a place for the standard flooded deep cycle battery. AGM's will sometimes cost 2 to 3 times as much as flooded batteries of the same capacity, although recently we have seen a dramatic price reduction. In many installations, where the batteries are set in an area where you don't have to worry about fumes or leakage, a standard or industrial deep cycle is a better economic choice. AGM batteries main advantages are no maintenance, completely sealed against fumes, Hydrogen, or leakage, non-spilling even if they are broken, and can survive most freezes. Not everyone needs these features.

No Equalization Charging. Unlike the more “Flooded” type batteries, equalization charging to extend the life-time of the batteries that some charge controllers allow for “automatically” are not to be used. In fact, this will decrease the lifetime of AGM batteries due to electrolyte loss via the vented valves supplied. Once electrolyte is expelled it is lost forever. However, this is one less maintenance headache that the user has to concern themselves with. Plus there is no need to ever refill the batteries with distilled water, for the lifetime of the battery.

So when considering solar systems for our national colleagues to use, the combinations of increased safety, easier transport, no-refilling and no equalization charging are considered great advantages.

Each manufacturer of lead-acid batteries has their own system of stamping on the unit the date of manufacture. This becomes important for AGM style batteries especially as their capacity generally degrades in time “just sitting around” on the shelf. This can be an important factor in a third-world setting, where the supplier in a port town, has had stock sitting around for a very long time, and the store- reseller has not taken the time to maintain a trickle charge of the batteries while waiting for sale.

If possible, contact the manufacturer of the given part directly on email and convince them (if possible) to tell you their system of date code stamping. Then you can easily verify the claim that the given stock you are about to purchase indeed has been manufactured recently.

All gelled (Gel Cell) are sealed and are “valve regulated”, which means that a tiny valve keeps a slight positive pressure. Nearly all AGM batteries are also sealed valve regulated (commonly referred to as “VRLA” - Valve Regulated Lead-Acid). Most valve regulated batteries are under some pressure - 1 to 4 psi at sea level.

“All deep cycle batteries are rated in amp-hours. An amp-hour is one amp for one hour, or 10 amps for 1/10 of an hour and so forth. It is amps x hours. If you have something that pulls 20 amps, and you use it for 20 minutes, then the amp-hours used would be 20 (amps) x .333 (hours), or 6.67 AH. The accepted AH rating time period for batteries used in solar electric and backup power systems (and for nearly all deep cycle batteries) is the “20 hour rate”. This means that it is discharged down to 10.5 volts over a 20 hour period while the total actual amp-hours it supplies is measured. Sometimes ratings at the 6 hour rate and 100 hour rate are also given for comparison and for different applications. The 6-hour rate is often used for industrial batteries, as that is a typical daily duty cycle. Sometimes the 100 hour rate is given just to make the battery look better than it really is, but it is also useful for figuring battery capacity for long-term backup amp-hour requirements.”¹⁰⁾

So what is our expected performance per average netbook? How long can we reasonable expect to supply power to a netbook while in use in the day? Consider this graph from Power-Sonic (right).¹¹⁾ Reading the chart to the right, let us consider a typical low power Asus 1101 HA netbook, that is running at 0.80 amps and while in use during the day. To reach the LVD point of 12.5 volts (see “depth of discharge”-next section) one would expect a “run time” of approximately 6 hrs. But this assumes that there is no supplemental solar energy also going to power the device even during heavily overcast days. Reality can yield much better performance than indicated in this pure load chart. With some of the new third generation solar panels, the “shade” performance is quite exceptional. It is not uncommon to see on an “overcast” day, enough solar energy to be completely sustaining a netbook, via the solar charge controller alone, while leaving a small “trickle charge” left over for charging the battery at the same time.

So, does one need to specify an 18 Ah battery, or a 35 Ah battery for everyday use? The answer depends upon the number of expected work hours for the end user, and also the number of expected “totally overcast” days, per average week. If the realities of village life means that one can only expect 4 hours of good day-time work, due to village level obligations to family members, then probably an 18 Ah battery would suffice. If the user is going to truly work 8 hrs a day, and perhaps 3 of those hours will be into the evening, then certainly consider purchasing a 35 Ah battery instead. If 12 volt house lights are in the equation, then go further, but also go for larger solar panels than 40 watts.

Remember that if one constrains the work to only during the day, it is possible with a 30 or 40 watt solar panel to completely remove the battery from this circuit entirely (in theory). The panel, even in overcast conditions, would charge the netbook's internal battery, and certain netbooks are capable of running 8-10 hours now on their internal Lithium Ion batteries. Such a “battery eliminator” circuit might be advantageous to fight off potential familial demands to use the battery elsewhere, a perennial problem in the field.

A very important factor for battery lifetime is the average level of discharge over the lifetime of the project. Basically lead-acid batteries are designed to be fully charged at all times. While using the batteries, the overall level of discharge should be keep to a minimum, and still achieve daily work goals that are practical for the given work conditions. Consider this chart: ¹²⁾

A consistent “depth of discharge” (DoD) of 50% (above) will yield a standard lifetime of 1000 charge/ discharge cycles per battery. If the user is constantly using the system each day, and recharging via solar, one would only expect their lead-acid batteries to live for approximately 3 years. This discharge level corresponds to 50% of the usable electrolyte solution and an operating voltage at the terminals of 12.5 volts.

However, if the user consistently discharges to the 30% level, or approximately 12.7 volts then the battery lifetime jumps to 2000 charge/ discharge cycles. Suddenly lifetime moves out to 6 years without the need for battery replacement.

Since the price of solar and netbooks is rapidly decreasing, but lead-acid batteries are not, this DoD issue needs to be monitored closely. Note too that “total lifetime kWh” peaks at the 30% discharge level.

The goal of the solar controller is to protect the lead-acid battery, while allowing useful work to be done as required from the battery. As we have seen, the total number of solar cycles for the lifetime of the battery is dependent upon the average LVD cut-off (there are other factors as well). “Capacity” or the ability to store a given amount of energy is 100% for a newly acquired battery, but diminishes over time. Capacity can be monitored in the evenings for a “no load” situation. Using a Digital Voltmeter (DVM) at the battery terminals, turn off all loads including the netbook, any lights and anything else attached to the battery (you can leave the solar controller connected), and then refer to this chart on the right to see your present battery status.¹³⁾

So if my battery was held at a float voltage of 13.7 volts during the day in good sunshine, but at dusk with no load, the voltage at the terminals was found to be 13.0 volts or less, then one can conclude that your battery is at 80% of its normal capacity. It has “aged” that much, where age is relative term here, and not based on the actual number of days of use. Note that temperature has an effect here too, but is beyond the scope of this particular paper. See reference for such details.

A very interesting technology, yet to be fully tried in field situations, are NiMH (Nickel Metal hydride). They are considered far more expensive to implement than lead-acid chemistries. However, one must note that this chemistry can undergo a full, repeated and cycled discharge, up to a 1000 cycles and also discharge levels can be to practically the zero volt level without harm. Since lead-acid batteries must be “over-specified” to work successfully (LVD at 12.5 volts), and therefore greatly reduce their “working capacity”, it might be economically better to “under-specify” NiMH batteries since they have a much better “depth of discharge” capability.

In other words, we may be by-passing NiMH technologies because of an “apparent” cost differential that is perceived as way too high, when the reality is different for a given low power application. This would require further research and perhaps a different kind of solar controller.

Lithium Ion technologies - common in laptop computers themselves for their high energy density - are so far ignored due to safety issues. There are innumerable reports of charger circuits failing and abused Li-Ion batteries going up in flames. It would not do to promote these technologies at this time, and find whole village houses burned to the ground due to miss-handling of equipment. At present these are not recommended as an external battery option.

For relatively long runs, such as the roof top solar panel to the solar controller inside the house, care must be taken to have a suitably large enough wire diameter. This is to minimize the loss of solar energy due to heat or resistance losses. The chart at the right¹⁴⁾ is for a 2% voltage drop for runs of copper wire as measured in feet. Other kinds of metal wire have a different resistance.

We are recommending #10 gauge (6 mm²) or #8 gauge (10 mm²) copper wire runs, but obviously this increases cost per foot or meter if you use more expensive #8 gauge wire. If you must use #12 or #14 gauge, then be sure to adjust the Xantrex C-12 controller accordingly to get the right results at the battery terminals, where it counts - NOT the controller terminals where it doesn't count. Feel free to adjust as necessary, the LVD, RVD, LVR and HVR levels for the battery type you are considering.

If you are purchasing wire from the USA, then diameter is measured by AWG number. However Europeans and other Commonwealth countries often sell wire by the square millimeter. Here is a rough conversion chart to help at right.¹⁵⁾

Circuit Breakers are designed to interrupt the circuit when a short-circuit of some kind has occurred. An example would be a wrench or screw-driver falling into powered electrical equipment. Or perhaps a short across the exposed Morningstar Controller connectors. Usually they are wired in series near the battery's positive terminal.

This 7 amp unit (at left) was found on the back panel of a broken UPS unit, and was greedily scrounged before heading to the rubbish tip.

Inline fuses are similar to what you see in automotive fuse panels. There is typically a style of holder with wires that can be attached. They are relatively common, but once they are used to protect equipment they must be replaced with spares. Not having a spare available, encourages one to bypass the fuse altogether to carry on with the work. Not recommended for sustainable national coworker systems.

Most netbooks are 19 volts input, however, in the beginning of the Asus line there were 12 volt input models. Originally this was thought to be a profound advantage, because perhaps an auto-style DC adapter might not be necessary. In the end, it was still required to clamp solar panel voltages to a solid 12.3 volts coming off the solar controller and battery. Such a suitable adapter was found for under $20, and could handle certain amounts of user abuse, such as short-circuits and reverse polarity.

All netbooks today are 19.5 volt models. It appears to be the product of easier rechargeable cell stacking, where cells do not have to be so tightly “matched” as in the 12 volt design. We have found a very nice inexpensive 3 amp, 19.5 volt auto-adapter for under $10, shown here. The goal of this final stage is further conditioning of the 10-14.5 volt output from the solar controller to the required 19 volts for the netbook to run and charge its batteries. This would be called a 12 volt DC to 19 volt DC converter in engineering terms.

The unit (right) is a relatively small box (3.25” L x 1.4” W x 1.1” H 85mm x 34mm x 27mm) with a charge indicator LED and found on eBay.¹⁶⁾ Just search for: “Battery Car Charger Cable for Asus Eee 1101HA”. The seller in the USA is “hey262mobile”; In Australia: “Lee262mobile” This unit has the correct DC connector for the machine's DC input jack (and those would be otherwise very hard to find). Rated: DC 11-14VDC OUTPUT: 19VDC 2.1A. We have stressed this to 2.8 amps and the box stayed cool to the touch.

From the beginning of the netbook phenomena Asustek has been producing their Asus Eee line of netbooks. CTS at PNG Branch (tech repair) had found these to be well built machines, and a PC-Magazine (on-line subscription) recently gave top honors to Asus with a mere 6% return rate by users, within the first year. This high reliability rate is exceeded only by Apple's line of notebooks. Meanwhile Dell and Toshiba lines continue with an approximately 23% return rate.¹⁷⁾)

Recently our CTS department has begun to look at the Dell line for overall construction and ease of repair, although still not yet popular at least by end user sales in the Branch.

A most important feature for the Asus line is that “Boot on SD Card” capability. Basically a suitably prepared SD card can have a complete Operating System environment on board, and if the SD Card is made properly the netbook can boot up a completely different OS with a custom and simplified user environment. See the discussion on BaLSA in another section.

Netbooks are ubiquitous now and countless makes and models are coming out from Asus to Acer… from Samsung to HP… from Toshiba to Dell to Lenovo. Name a manufacturer that doesn't make a netbook of some kind besides Apple? (which makes the iPad instead).

Assuming you've done your research - then on the Internet head for DealNews.com and a “Netbook” search.¹⁸⁾ Then look for all the “deals of the day” of all the online stores and all the makes and models of netbooks. The best system at the best price is a daily moving target.

Be sure to work with a reputable store that you have worked with before: Good companies include: buy.com, bestbuy.com, newegg.com, frys.com, amazon.com, (any major office supply store), dell.com, tigerdirect.com, mwave.com and B & H Photo. There are others of course. Also look for deals that include extra installed main memory, especially if you are doing Windows and not Linux.

A wonderful early netbook entry was the Asus Eee 1000HE which represented a 12 volt input system, boot on SD card, but a potentially limiting 10 inch 1024 x 600 pixel screen. Backlighting was bright and LED powered, which helped it reach a standard steady-state operating current of 0.9 amps at 12 volts coming from the solar controller. It was based on the older Atom N270 series, which was a little bit more power hungry, but still very acceptable. Highly prized for its “matte” style screen, there was improved readability in high glare situations, such as those found in village houses. 10 inch netbooks are considered the minimum for comfortable touch typing with a slightly reduced keyboard than “normal”.

Problem: Discontinued Model end of 2009; replaced by newer models.

Even better was the Asus Eee 1101HA model which has a much better 11.6 inch screen resolution at 1366-by-768 pixels. This is important for Paratext users and anyone else trying to manage many open windows at one time to do real work. LED backlighting and the N280 processor produced even better power consumption as revealed with a 0.8 amp standard steady-state current as measured from the solar controller. Sadly, the one problem with the 1101HA was its “glossy” style screen. This is considered less desirable, but national coworkers seem to prefer the larger screen and keyboard, despite this limitation.

Problem: Discontinued model end of 2009; replaced by newer models.

In 2010 we witnessed the advent of significant new designs representing the convergence of mobile phones and netbooks, sometimes called “smart-books”. The best designs are ARM processor based which is the most popular mobile phone architecture and present in the wildly popular Apple iPhone and the just announced iPad. These “smartbooks” represent power consumptions of a mere 2 watts compared to the 8-10 watts of Intel Atom based Netbooks. Ultimately this would translate to much smaller solar panels and much lower costs per user.

One problem with the ARM architecture is that Windows will not normally be found there but another OS such as Linux, Moblin, Android or something else (for now). However, besides lower power consumption, these “smartbooks” feature an “instant on” capability, like mobile phones and for some that can be an distinct advantage.

Designed to be a complete software environment for lay men and women to complete aspects of the language development task, BaLSA or “Basic Language Software Appliance” is designed to have a very easy to use interface for people who have not had any prior experience with a computer before in their cultural frame of reference. The present popular Operating Systems such as Windows, Mac OS X, or Linux are considered way to complicated, demanding a knowledge and experience “bar” that is set way too high for average citizens of the third-world. All necessary language development software to assist in translation, literacy and language documentation tasks are present to use.

The environment is “bootable” and can be hidden from the user when placed in total onto an SD card and inserted into the machine. In fact, machines can be set up without the user even knowing the SD card is in place. Advantages to the environment include:¹⁹⁾

• Outside Mentor Adjustments
• Language Localization Capabilities
• Presentation Modifications (User Icons hidden or displayed)
• Robustness (When the system is corrupted, simply insert a new SD card)
• Extremely easy historical backup of data, in multiple places

Paratext is a popular Bible Translation tool in use in the field by SIL members and national coworkers alike. At present, it is only Windows based. A very exciting new collaboration feature in version 7.x allows for simultaneous work by more than one worker, across networks, the Internet and also pluggable USB “memory sticks”. When on a network the differential changes to the database are manageably small, hence updates to the database can be made using very slow communications links on the Internet. This has been shown to work across HF-Radio email links.

WeSay²⁰⁾ is a vernacular dictionary program designed from the beginning with “ease of use” in mind and for national citizens to utilize well, without significant prior training. Particularly targeted are vernacular users who may not have encountered a computer before to document their own unique language.

“WeSay helps non-linguists build a dictionary in their own language. It has various ways to help native speakers to think of words in their language and enter some basic data about them (no backslash codes, just forms to fill in). The program is customizable and task-oriented, giving the advisor the ability to turn on/off tasks as needed and as the user receives training for those tasks. WeSay uses a standard xml format, so data can be exchanged with linguist-oriented tools like FieldWorks. Users can collaborate via USB flash drive, email, and (soon) via network connections [or the Internet.] Users are able to make local, simple printouts for local use, checking, and PR work.”²¹⁾

The “ideal” Literacy Application has a similar targeted audience to WeSay. It is recognizing a huge need in counter-response to the software industry's pressure for more complex and powerful Desktop Publishing (DTP) systems. This is the opposite of our need here.

This app would create a low-training, high-output system where mother tongue speakers and their advocates work together to foster both community authorship and access to external material in the vernacular.²²⁾

Like WeSay, there are two intended users:

• The primary user is a Mother Tongue Literacy Worker. He/She has basic computer skills, and little access to technical help.
• The secondary user is the Advisor/Advocate. He or she has more advanced computer skills and lots of access to technical help.

Templates: Keeps things simple by replacing many of the operations of normal Page Layout applications (flow, size, format, crop, etc.) with ready-made templates. Templates can be “blank” or content based on standard templates can be brought to the work for re-use or for making derivative works.

Library: Works by others can be accessed easily in a re-usable library. Derivative works can be published with concern based on a Creative Commons license for the work. All worked entered into the Library have all permissions granted for re-use.

Citation Management: Necessary author permissions are recorded for future reference (and proof of Creative Commons license permission, when asked).

Text Sizing: Designed with easy to use controls, for both text and illustrations, to facilitate composition differences between languages.

Illustrations: Royalty free illustrations can come from a pre-existing library, although custom drawings can easily be incorporated with simple to use controls. New illustrations must be “free” before re-submission into a common library.

Publishing Mode: Various common printing and collation formats are supported, and again with ease of use in mind. Example: Half A4 center stapled, with backed sides (duplex).

Created by John Wimbish, and sponsored by “The See Company”, “OurWord! is a Bible Translation software program designed for national translators, who are translating the Scriptures into the world's minority languages, and who typically have not had significant computer experience.”²³⁾

“Using a concept called 'manual adaptation' to refer to OurWord's process. the computer replaces words from one language with words in the other language in order to produce an initial draft. The translator still relies on the source language, but rather than receiving word-by-word suggestions from the computer, the translator crafts the translation himself ” mostly at the paragraph level filling in a prearranged form template with fields to fill in. “Thus he is able to address such things as resolving collocational clashes, deciding on appropriate idioms, etc.. By using a good source text, many man-years are saved that would otherwise be spent on activities such as exegesis and decisions on how to represent concepts within the language family and culture.”

Created by Teus Benschop, this GNU license program²⁴⁾ has many similar features as Paratext, but is less refined at this point. There would not be the collaborative team features of Paratext 7.x, for instance. However, it is the best Bible Translation software for Linux at the moment and the only tool of its kind to be found in the BaLSA system since BaLSA is based on Linux and a “free to give away” unencumbered” system. A companion tool is “BibleTime” a Bible Study program.

Adapt It was originally created by Bruce Watters. It is a Windows-based package that provides tools for translating either text or scripture from one language which you know, to another related language known to you or a coworker. No linguistic analysis is performed. Thus it can be an appropriate tool for native speakers who have no linguistic training. It has an easy-to-use interface designed for users not normally familiar with computers before.

We are on that threshold where appropriate and robust technology may launch us into a new era of involvement by third-world nationals that would not otherwise be able to participate in the work of vernacular Language Development. The dream is to provide the tools (and training) necessary to encourage native speakers of a given vernacular to take pride in their own language and culture; to begin to document their mother tongue for themselves and to consider the translation task as well. Given in the harsh realities of our limited expatriate man-power to complete the task, it is time for the citizens of the third-world to enter into this exciting work as well. In new ways, it may be possible for national citizens to be encouraged to join us in the work.

Brian Chapaitis originally studied electrical engineering at Cornell University, USA. He is comfortable with programming embedded micro-controller systems, and thus is a “hardware and software” man, although he considers “real programmers” to only work in assembly code <grin>.

Together with wife Helen (physician), they have served in a variety of positions in the SIL Papua New Guinea Branch for over 20 years.

Brian presently works out of the Language Software Services office in the SIL LCORE department building at Ukarumpa, in the Eastern Highlands Province, Papua New Guinea. He can often be found way off center, ministering within the church in the local village context. He shares the growing vision of empowering national counterparts to do aspects of the Language Development task hitherto thought impossible, with self-sufficiency, using the latest new appropriate technologies, both hardware and software.