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- Half Watt polycrystalline (not amorphous) high efficiency photovoltaic panel.
- Six narrow angle high efficiency LEDs for task light illumination
- Three wide angle high efficiency LEDs for room illumination
- Three NiMH batteries - better for the environment. We no longer use NiCad batteries.
- High impact resistance ABS body & polycarbonate lens.
- Dimensions Length x Width x Thickness:
- Head/Body 9" x 3.8" / 2.4" x 2.3" / 1.3"
- Weight - 11 ounces / 300 grams
- SL2 - Full Data and Description
- Due to numerous detailed questions about the technical aspects of our new SL2 solar powered flashlight, our lead engineer has provided the following commentary, for those among us who really want to know everything they can about science and how things work. Enjoy, and we are pleased to field additional questions.
- The SL-2 Super BOGO light is intended to be a rugged, long life, solar rechargeable light whose primary purpose is for kerosene lantern replacement and task lighting in "developing world" applications. It's design brief was to provide wide angle illumination with more usable light than a kerosene "bottle lantern", for use in rooms up to 4 x 4 meters or as a study or work lamp over a table, while also providing a bright directional "task light" beam for when more directed light is required. In a kerosene lantern replacement role it can save users in excess of 20 to 30% of their disposable incomes while eliminating fine carbon particle inhalation (one cause of "hut lung") and eliminating injuries from burns due to kerosene spillage. And with hydrocarbon prices skyrocketing, kerosene prices are also way up, so what was a good deal six months ago, is now a great deal, purely from an economic standpoint.
- The features which make it suited to its primary role also make it a great light for use for camping, automobile use and as a light you can use in an emergency. Leave it where the sun shines on it and you will get hours of operation when needed. With a fully charged original battery the SL-2 will typically operate for 4 to 5 hours on full power, about twice that on its medium power settings and 4 times as long on low power.
- The SL-2 uses a high efficiency polycrystalline silicon phototovoltaic panel (or PV panel or 'solar panel') to charge its batteries. The charging capability is limited by the size of the panel would fit on the light. Depending on battery state it takes 8 to 10 "sunlight hours" (hours of direct full sunlight) to charge the supplied 800 mAh batteries. Users can choose to re-fit with larger capacity batteries which will take proportionately longer to charge. In African summer conditions a full charge will be able to be achieved in a single day. In less sunny conditions only a partial charge may be achieved in one day - it depends on the angle of light - your latitude at different times of the year, and how many hours of exposure you provide the panel. A light which is only occasionally used can accumulate a full charge over a number of days. When the light is in use every night (as it will often be in developing world use) the hours of use per night depends on daily sunlight hours. For cloudy days, the amount of light from the sun is reduced, however, so is the temperature in most cases, so the batteries work a little more efficiently - the lower the heat, the better the batteries work. The medium and low power modes allow users to reduce lighting levels to allow longer lighting times when charging conditions are poor. On full power users get about 30+ minutes of lighting per sunshine hour. On medium power they get about 1 hour of operation per sunshine hour. And on low power, about 2 hours operation per sunshine hour. So with 2 to 3 sunshine hours in a day a user can expect 4 to 6 hours of low level but useable light. And as with our SL1 light, placing the light at an angle to the sun, so the panel is tilted to receive the maximum amount of light available, instead of just setting it on it's face plate at 90 degrees, makes a big difference in power generation.
- When suspended vertically about 1 metre above a 2 x 2 metre (6 foot x 6 foot) table an SL-2 will provide enough light for reading or other work. The light levels are very low by mains lighting standards but surprisingly useable once your eyes adapt. On a smaller area, say 1m x 1m (3 foot x 3 foot) a number of people can still read or work usefully at substantially higher light levels. In all cases the light illuminates the surface better than a kerosene wick-lantern or bottle-lantern would.
- Unlike most other lights in its class, the light output of the SL-2 remains at the user selected level regardless of the state of battery charge (except as the battery nears the very very end of its capacity levels will fall off). To maximize battery life, operate the LEDs correctly and provide constant lighting levels the Sl-2 uses a "boost converter" - essentially an 'electronic gearbox', which takes the slowly dropping battery voltage and boosts it to a level suitable for providing a constant operating current for the LEDs. Unlike most LED lights the SL-2 operates its LEDs electrically "in series" so that the same current flows through all operating LEDs. This allows the current and thus the brightness to be closely controlled so that the LEDs are operated in the manner recommended by the manufacturers.
- When the battery capacity is almost exhausted the light will first dim, then flash, then the LEDs will turn off completely. A small amount of battery capacity remains and this is used to "keep alive" the control circuitry in a "standby mode". If a light which turns off due to a low battery condition is then exposed to sunlight it will charge its battery and then, when the sunlight is again removed, turn on again in the same mode as it was in previously. This feature allows the light to be used as an automatic pathlight, streetlight or nightlight. To achieve regular operation in this mode the light needs to be placed so that it is charged daily. (For 10 hours of night time, a light set on low will operate throughout the night when charged for 5 sunlight hours or more. If there are less than 5 sunlight hours available the light may turn off before dawn but will still usually operate well into the night. If the light is not charged the battery capacity will continue to drop. When it reaches too low a level the light will reset fully and the light will then draw no battery current but the last mode is no longer remembered. If a battery is removed or a battery "door" is unscrewed more than about 1/4 turn the light will turn off and the last mode will not be 'remembered'.
- When an operating light is placed in sunlight so that charging starts the LEDs will turn off. The light "remembers" what mode it was in and restarts in this mode when the sunlight is removed. If the light is charged for long enough to fully charge the battery charging stops to protect the battery from over charging.
- Battery capacity will decrease with time. Use of user installed larger capacity batteries can be expected to provide longer battery life both because of the extra initial capacity and because the batteries are not "deep cycled" so often in normal use. Battery capacity is measured in mAh (milliamp hours). Operating time on a fully charged battery is about mAh/200 hours. The initially provided batteries are 800 mAh capacity and will provide 4+ hours of full power operation. If users fit eg 2500 mAh batteries they can expect about 2500/200 = 12+ hours of operation. Charging time is about mAh/80 sunshine hours. So an 800 mAh battery will take 800/80 = 10 sunshine hours to fully charge and a 2500 mAh battery about 2500/80 ~= 30 sunshine hours. On a good day charging will exceed these levels but these are a good guide of what may be typically expected in full sunshine. Obviously it will take several days of full sunlight to fully charge a 2500 mAh battery. If desired batteries may be charged in an external charger - not something which will usually be required. Batteries will charge when light levels are lower than full sun, but charging will take longer. Charging starts with about 6% sunlight and increases approximately linearly with increasing light levels. A very bright but clouded sky can charge at 25% to 50% of maximum rate. When charging, to achieve maximum charge rate the panel should be angled to point as directly at the sun as possible. If leaving in the sun all day, angle the light so that it points at the "arc" in the sky that the sun travels over and so the light is pointing squarely at where the sun will be at midday. (Easier to do than describe). If desired the light can be moved several times during the day for best effect, but the gains are surprisingly small compared to aligning the light in its best position initially.
- Note that batteries MUST be inserted with all the positive ends DOWN (non-flat ends inserted first). The battery doors can be screwed home using a coin .
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