Solar Projects - Battery Boxes
There have been many turns in this project and lessons learned during our development program. As far back as 2010 when we began developing a solar infrastructure at MOH's "community development centers", Walter Brown and Paul Sigmund began collaboration on the concept of portable solar powered electric lighting, enabling villagers to charge a lantern at the MOH center, use it at home, and then return it to MOH's facilities for recharging.
We selected a commercially available rechargeable lantern, and after preliminary testing invested in 30 more. While designed to operate with it’s own mini-solar panel, we sought to charge the lanterns through our own solar centers. Our intent was to centralize our program, leasing the lanterns at a nominal cost, while maintaining connection to MOH.
The lanterns claimed to provide lighting up to 8 hours via a fluorescent bulb, and had the attractive feature that other devices could be plugged in to them, such as a cell phone, or small radio.
In 2011 we began our “Light-a-Village” program, and initially reported excellent results as the villagers experienced 8 hours of bright, well distributed lighting.
Our 2010 Light-a-Village fundraising campaign
After six months, we began receiving reports that the capacity of the lanterns was declining, eventually with villagers experiencing fewer than 3 hours of operation. During our next trip to Malawi we changed the batteries, but while initially restoring performance the lanterns eventually declined and failed once again. After two years the program was abandoned due to disuse.
During 2016 and 2017, we returned to our lantern dilemma, to give our considerable "fundraised" investment in lanterns one last chance. Removing the a circuit board, we designed an automated apparatus to cycle the lanterns through charging and lighting while recording voltages - each step involved hours of timing - too long to monitor manually. Our measurements again confirmed the lantern circuitry was both undercharging and under utilizing the batteries!
Not abandoning our vision, we began developing an entirely new concept. The 7.2 amp.hr batteries the lanterns employed were a optimal size in terms of “carry weight”, and capacity to provide 10 watts of power for 8 hours. What if we enclosed the same battery in a waterproof box with a handle, and the villagers could plug in one or two light fixtures they had installed at their home, to the box? But the battery charging would be controlled by our center controls. A "Battery-in-a-Box".
Other requirements:
4. Charge in 5 hours (Malawi effective sun power)
5. Provide 10 watts of power for 8 hours.
6. Work in conjunction with our MOH solar centers.
7. Charge at 14.2 vDC, with LVD set at 11.5 vDC.
We were able to source the components and assemble such a device for under $100, and after successful bench testing here in America, during 2017 we prototyped two units in Malawi. So far, after 8 months, we’ve been told by our Malawian friends that they are performing as designed. We will bring 12 more boxes online at Khwamba in September of 2018, and hope to expand to all of the centers in the future.
Working with Vladamir, we decided that the only answer, was the most simple one: bypass the lantern circuitry, and modify the lantern design to accommodate the newer and much more efficient corn LED bulbs. LED’s do not need the additional circuitry required to run a fluorescent bulb that the original lantern circuitry had to provide. We could simply utilize the lanterns as portable “lamps” that could be plugged into our new battery-in-a-box and retain have all of the originally envisioned functions to make village life easier.
To do this, we had to develop adapters to hold and elevate the LED bulbs to the necessary height in the lantern. These we machined from heat resistant polymeric roundstock. Measurement of illumination level appeared equivalent. Power requirement should be about 50% lower. We will be prototyping these retrofit lanterns in Malawi in 2018! Now our lantern investment can be recouped and used for a good purpose!
Through the wonders of the Internet, we recently discovered there is a commercial venture of “battery-in-a-box”, similar to ours in Kenya, through a consortium of Osram, and the European Union. How about that? Proof of concept?
lantern light for preparing an evening meal
In Malawi, our experience during overnight visits at the home of Khwamba director Felix Khonje clearly demonstrated how difficult life can be in the absence of electrical lighting. While kerosene lanterns are used, fuel is expensive, floods enclosed areas with polluting gases, and is a fire hazard.
camera flash shows what's really there
. . . . now imagine the scene with only a candle or flashlight?
Preliminary testing and evaluation of a lantern carried home revealed the built-in circuitry was not allowing the battery to fully change, and also that it was over-protecting the battery from excessive discharge by turning the lantern off prematurely. The manufacturer offered to replace the batteries, but we already had proven that not to be a viable solution.
While we continued installating solar generation to MOH’s facilities for lighting, we lamented failing in our objective of “carrying electricity home”.
It is known that 12 volt batteries must at least be charged at 14.2 to 14.5 vDC, and if not, their capacity will deteriorate by a process known as sulfation. Charging voltage levels are even printed on the battery case!
Our testing revealed the lantern’s built-in circuitry was regulating the charging voltage to the battery at only 12.8 vDC! As a result, not only were the batteries not being charged to their full storing capacity, but the low charging voltage was shortening battery life. Hence the shortened battery life would be expected!
Lanterns at Khwamba
2011
Battery powered devices must contain a circuit to prevent the battery from being damaged by removing too much of it's charge, i.e. drawing the voltage down too far. This protection function is called low voltage disconnect (LVD). For a 12 v battery, a safe low voltage cut-off is approx 11.3 to 11.5 vDC. Some systems are designed with a LVD as low as 10.7 vDC!
Our tests demonstrated the lantern circuitry was turning the lantern off when the voltage only had dropped to 11.8 to 11.9 vDC, much too high!
Because the operating voltage range of the batteries were too low, the light interval was too small.
In 2017 we reformulated a program we have long sought to accomplish: enabling villagers to carry home the electricity our solar installations are generating, making their homes and home life more pleasant and nightly tasks easier. We have developed a battery-in-a-box that integrates with our solar centers and allows up to 8 hours of operation of one or two LED lightbulbs that remain in a home, but may be plugged into the box. It is our objective to maintain MOH as the central connection to all that we do. Now with 8 months of successful operation of two prototype boxes at Khwamba village, we plan to expand the program in 2018 to a dozen boxes.
Each lantern's control circuitry is housed on an internal circuit board. Having confirmed the problem, could we (somehow) modify those circuits? We are not electronics experts but the Lord, through the Internet, led us to the assistance of an electronics engineer. Vladamir, who lives and has a workshop 30 kilometers East of Moscow, offered to help us! We mailed him one of the lantern circuit boards for testing, and together we concluded there was no way to modify the settings of the circuit. Nevertheless these experiences are "all part of the story!"
What else would be needed?
1. A switch to turn on the power
2. A fuse to protect against output shorting
3. An on-board low voltage disconnect (LVD) to protect the battery from over-discharge
Issue #1: Charging the battery
Issue #2: Protecting the battery
A new direction
But what about all those lanterns?
Another "side-story"
Yes, we will use the lanterns!
Our home team worked diligently to assemble and wire boxes for use in Malawi.
