The lamp

It is made up of 4 components: (1) LED bulb (2) switch (3) cellphone battery rechargeable in any cellphone (4) solar PV (5) locally available materials such as empty transparent bottles, which make it easy to build and repair by users at the village level. All the components are chosen in such a way that it doesn’t require a control system, which drastically reduces the price of the lamp, making it the world’s cheapest lamp.To increase trust in the lamp, we have developed a specific training method combined with a community approach, which empowers people with real understanding of sustainability and basic knowledge to build a solar lamp. Check out sample lamps.  Please read FAQ also. 

Caution:Making lamp without the training

If everyone starts making the lamp without going through the teaching/training, the lamp last only for 1+ year, it will lead to massive supply for mobile battery and solar PV which is harmful for the nature and also people will loose trust on solar technology, so instead of making them aware , it will destroy whole solar market. Also, without proper training of knowing components specification and taking safety precautions, this might be dangerous for the people, as battery and LED can explode.

Here is brief technical description:

LEDlamp is unique because of its simplicity.We were able to remove the battery controller, which reduces the cost drastically and also the complication to build it. All the components have been chosen in such a way that they nullify the requirement of extra components such as voltage controller, current controller, resistors, capacitors, charge controllers etc.

We use Li-ion mobile batteries (cell phone batteries), which need to be operated between 3-4 Volts to increase its life cycle. Further, it shouldn’t be charged beyond 4.2 Volts, to avoid overcharging. Considering these constraints, we use LED for lighting as it operates between 2.7-3.2 Volts and a current limiting resistor, hence it stops working (current through the LED below 1 mA) when the battery voltage is under 2.7 Volts, which gives indication for charging and also prevents the battery from deep discharge. Further, we use solar PV (Vmp=5 and Imp=100mA), which is ideal for mobile battery as we are using blocking diode which has drop of around 0.7 Volts, hence preventing from overcharging. Also, as the battery voltage approaches 4.3 Volts, solar PV current decreases to 5-10 mA. 

Further, we use STDP switches (Single throw double pole), which can act as both the switch of the lamp and when it is switched off, the charging circuit.

FAQ

Q: Why LEDsafari lamps are cheap?
A:  We use basic components, we do not have manufacturing costs (self-assembled) and we use material that doesn’t cost for the structure (e.g. PET bottles).

Q:  Why not make and sell these lamps instead of training? Since, it is cheap, people will buy it.
A: The price of solar lamps is not really an issue for the people. One professional lamp (e.g. D.Light) costs 10$ and people in Africa already spend 2$/week for kerosene. So in 5 weeks they have break even. On top of that, D.Light offers a 3 years warranty, so they have an amazing deal. The question is why they still don’t buy these professional solar lamps. It is because the people don’t understand what is so good about solar lamps and don’t trust the product (it comes from China and if it breaks they cannot repair it).

Q: How long lamp can last?
A: 1+ year and we are constantly working on improving the life.

Q:  Why dont you include some more components to make it last long?
A: The current lamp design (with 5 complimentary components) is suitable to make anyone understand how it works. If we increase the components, the understanding and assembling process will be complicated and it is outside of the LEDsafari framework. We are working on designing better lamps which will last long. Its an on going process. Thats why open-source is important because everyone can contribute to this idea.

Q: What is the worst thing that can happen if people handle the batteries in the wrong way?
A: Explosion or if it a short circuit then people might get burn.

Q: Am I correct to assume that these problems can’t occur with professional lamps where the battery is not removed?
A: This is hard with professional lamp because batteries are hidden and away from user control. In our case, user need to fix the battery.

Q: If so: could this problem be avoided in the LEDsafari design if the battery was integrated into the lamp in a way that makes sure that the battery cannot be removed?
A: Yes, could be but then its just a normal lamp. Its no more a Do-It-Yourself . We used mobile batteries because these batteries are available every where and people can just change the battery if battery has gone bad. We need to use different kind of battery. Our technical team is working on that.

Q:  How do you plan to take care of the waste materials? e.g. batteries etc.
A:  Regarding the recycling system for batteries, we are definitely looking into this. We are thinking on how to make sure that people recycle the batteries, not only from the lamp but from their cell phone or any other device. For this we are considering to partner with local NGOs or government organisations.