Low-tech Solar Lamp With Reused Batteries

This tutorial allows you to make a solar lamp equipped with a USB charger. It uses lithium cells that are reused from a old or damaged laptop. This system, with a day of sunlight, can fully charge a smartphone and have 4 hours of light. This technology have been documented during a stopover of the " Nomade des Mers " expedition on the island of Luzong in the northern part of Philippines. The association Liter of Light has already installed this system since 6 years in remote villages which don't have access to electricity. They also organize training for the villagers in order to teach them how to fix the solar lamp ( already 500 000 lamps installed).

The original tutorial, and many others to build low-technologies, are available on the Low-tech Lab's website.

Lithium is a natural resource whose stocks are increasingly used for electric cars, telephones, and computers. This resource is gradually being depleted over time. Its increased use in battery manufacturing is mainly due to its ability to store more energy than nickel and cadmium. The replacement of electrical and electronic equipment is accelerating and it is becoming an increasingly important source of waste (DEEE: Waste electrical and electronic equipment). France currently produces 14kg to 24kg of electronic waste per inhabitant per year. This rate increases by about 4% per year. In 2009, only 32% of young French people aged between 18 and 34 years old, have once recycled their electronic waste. In the same year 2009, according to Eco-systèmes, from January to September 2009, 113,000 tonnes of CO2 were avoided through the recycling of 193,000 tonnes of DEEE, one of the four eco-organisations in the DEEE sector.

However, this waste has a high recycling potential. In particular, lithium present in the cells of computer batteries. When a computer battery fails, one or more cells are defective, but some remain in good condition and can be reused. From these cells it is possible to create a separate battery, which can be used to power an electric drill, recharge your phone or be connected to a solar panel to operate a lamp. By combining several cells it is also possible to form larger device storage batteries.

Supplies

• Used laptop battery
• Solar panel 5V-6V / 1-3W Charge and discharge regulator (ex: 4-8V 1A Mini Li-ion USB Arduino Battery Charger TP4056)
• DC/DC tension converter DC/DC booster MT3608 (electrical component that will transform the 3.7 V of the batteries into 5 V)
• High power LED Lamp (ex : LED boutons 3W )
• Switch (to open the circuit and cut off the light)
• Electric tape
• Box

Tools

For cells extraction:

• Gloves (to avoid cutting with the plastic of the computer battery or with the nickel ribbons that connect the cells)
• Hammer
• Chisel
• Cutting pliers

To build the lamp itself:

• Glue gun (and glue sticks)
• Heating gun or small torch
• Wood saw
• Screw driver

This tutorial shows how to recover computer cells to make a new battery. Powered by a solar panel, or by a USB port, it will allow you to light an LED lamp.

The system works around three modules:

• the energy reception module: the solar panel and its charge controller
• the energy storage module: the battery
• the module that gives back the energy: the LED lamp and its voltage regulator

Energy Receiving Module: Photovoltaic Panel & Charge Controller

The photovoltaic panel concentrates the energy of the sun. It allows to recover its energy in order to store it in the battery. But be careful, the amount of energy received by the panel is irregular depending on the time of day, the weather... it is important to install a charge/discharge regulator between the panel and the battery. This will be protected against overload, among other things.

Energy storage module: the battery

It is composed of two lithium cells recovered from a computer. To put it in a nutshell, a battery is a bit like a box containing several batteries: each of them is a cell, a unit that supplies power to the device by electrochemical reaction.

The cells found in computers are lithium cells. They all have the same capacity to store energy, but their ability to make it is different for each. To form a battery from cells it is important that they all have the same ability to deliver energy. It is therefore necessary to measure the capacity of each cell to compose homogeneous batteries.

Module that renders the energy: the LED lamp, the 5V USB port and its voltage converter

Our battery supplies us with 3.7V power and the LED lamps we used operate at the same voltage. In addition, the USB ports provide a voltage of 5V. We therefore need to transform the cell energy from 3.7V to 5V: using a voltage converter called DC/DC booster

Here are different steps necessary to build the lamp :

1. Removing the cells from the computer battery
2. Measure voltage of cells
3. Realisation of the 3 modules (solar panel + charge regulator battery LED light + charge regulator)
4. Linking the 3 modules
5. Building a box
6. Integration of modules in the box

For this part we suggest you to look at the following tutorial : Batteries recycling.

1. Put on gloves to protect your hands
2. Put in place the battery, and open it with a hammer and a chisel
3. Isolate each cells by removing every other parts (as shown on the photo).

• Measure voltage:

We start by measuring the voltage of each cells in order to check if they are working properly. Every cells that have a voltage lower than 3V will not be able to be used in this project and should be recycle.

Using a multimeter, in DC mode, measure each cells and check the one that are usable ofr the project.

Be carreful : If the computer battery seems to have liquid on the outside, do not open the box, lithium is harmful in high dose.

• Measure capacity :

To measure the capacity of a cell, we have to charge it to the maximum and then discharge it. Those cells are lithium based, and need a specific charge and discharge system, ususally the maximal charge is 4,2 V and the minimum is 3V. Going over those limits will damage the cell.

1. Use a PowerBank : it will alow you to charge many cells at once with a USB port.
2. Charge the cells and wait until the charge is complete (all the light should be on), it will be done in about 24 hours. (image)
3. The cells will be charge at their maximum (4,2V), now we have to discharge them. You should use an Imax B6 : a tool that allow to discharge the cells and check their capacity. How to use the tool :
   1. the voltage : it will ask you which type of cells you would like to check, you should choose the lithium one. It will automatically regulate the discharge at 3V minimum.
   2. the intensity : set to 1A in order to have a quick and secure discharge. In this condition, the discharge should take between 1 hour and 1 hour and half.
   3. Connect the magnet to the crocodile clips, then connect to the cell, the magnet help to let the current pass through the Imax B6 to the cells. (image)
   4. Discharge the cells until they are completely empty.
   5. Note the capacity on the cell. The higher the better.
   6. Sort your cells by capacity : <1000 mA, between 1000-1300, 1300-1500 and >1800 mA.

Remark : It is important to do homogeneous batteries, with cells that have a similar capacity

Module 1 : Solar panel and charge regulator

• Use a black and a red wire, use a pliers to stripe the wires.
• Solder the red wire on the positif side of the panel and the black on on the negative side.
• The charge regulator has 2 inputs : IN- and IN+ (which are indicated on the component) : Weld the red wire (positive) with the IN+ input of the charge regulator and the black wire (negative) with the IN- input (image 5).

Module 2 : Battery

• Insert the lithium cell in the battery holder.

Module 3 : LED / USB converter

The voltage converter DC/DC has two inputs and two outputs : Inputs : VIN + and VIN - / Outputs : OUT + and OUT -. The LED has two input wires : one positive and one negative.

• Take two wires (red and black).

• Weld the red wire with the VIN+ input of the voltage converter and the black wire with the VIN- input.

• Caution: Wire polarity is not indicated on the LED. In order to identify it, use an ohmmeter. The wire is positive when it displays a null value. When it displays a higher value, the wire is negative.

• Weld the LED positive wire to the OUT+ output of the voltage converter and the LED negative wire to the OUT- output. (image)

The charge regulator has 2 inputs : IN- and IN+ (which are indicated on the component).

1. Weld the red wire of the solar pannel (positive) to the IN+ input of the charge regulator and the black wire (negative) to the IN- input.
2. The charge regulator has 2 inputs : B- and B+ (which are indicated on the component). Weld the red wire of the battery holder (positive) to the B+ input of the charge regulator and the black wire (negative) to the B- input.
3. Weld the red wire (positive) of the USB/LED converter module to the OUT+ output of the charge regulator. Weld the black wire (negative) to the OUT- output. Remark : The electric circuit is now closed and the light turns on.
4. Cut the positive wire connecting the regulator to the converter in order to open the circuit and weld the switch in series. It will be used to open and close the circuit.

Version 1 : Tupperware

This design originates from Open Green Energy, do not hesitate to consult the original tutorial. We are sharing it because it seems really interesting. However, the case shall be adapted to our circuit, in particular for the USB output. We will propose soon our own model inspired from this design.

Version 2 : Large size thermoformed bottle

This model allows the circuits to be completely waterproof, but requires specific materiel :

• One 5L water can
• Plywood boards (or raw wood) between 1 and 2cm thick
• A cleat, minimum length 80cm, width between 3 et 5 cm

Building the two bases:
These are the two ends of the lampe, the upper hosts the solar panel on one side and the electric circuit on the the other. The lower end is used to close the lamp and seal it impermeably.

1. Cut out 2 boards of 15/13cm and 2 boards of 11/13cm.
2. Overlay each small board on a biger one, paying attention to place it at the exact center of the big board. Each pair of boards will be screwed later.

Remark: For waterproofness, it is better to varnish the boards beforehand.

Building the mold:

1. In the cleat, cut out 4 portions of about 20cm.
2. Place them in each corner of one of the already cut small boards (11/13cm) and screw each cleat portion with the board.
3. Place the other small board at the other end of the four portions and screw them in the same way. The result is a cuboid of dimensions 11/13/20, which will be used to thermoform the plastic bottle.

Thermoforming the lamp envelopp:

1. Cut out the bottom of the 5L bottle and insert inside the mold vertically (the 20cm side of the mold should be parallel to the side of the bottle).
2. Heat slowly with a thermal stripper each side of the cuboid. The stripper should be approximately 10 cm far from the bottle. If you don't have a thermal stripper, it is possible to use any other kind of flame source (such as a gaz heater for example).
3. Once the bottle obtains the same shape than the mold, continue to heat in order to erase the bottle patterns and to stretch the plastic properly. Be careful not to heat to close to the plastic or too long in the same place, otherwise bubbles will form at the plastic surface.

4. Leaving the formed bottle on the mold, cleanly cut level with the mold the upper part of the bottle, and cut again the bottle about 17cm below.

5. Once the cutting is done, unscrew the cleats on each side of the mold in order to separate the mold from the plastic.

6. At each end of the formed bottle, fold 1cm wide tabs at 90° towards the inside. Each tab should be bevelled on both sides (such as shown on the photo). The tabs will slip between the two boards (the big and the small one) at each side of the bottle, to improve the lamp's sealing. In order to fold easily the tabs, trace a thin line with the cutter on the inside of the bottle and fold it with the hand.

Fixing the solar panel :

1. Place the panel on the bigger board, mark the position of the + and - outputs of the pannel and drill a hole of 5mm in both boards. (If any component is already in this place, the hole should be moved).
2. Put the wires from the charge controler in these holes, and weld them to the corresponding outputs on the solar panel.
3. To attach the panel, the ideal is to use a thin layer of fabric sticked to the board and to glue the panel on the fabric (using strong glue for example).
4. For the lamp base, repeat the same operation at the other end of the plastic.
5. Place the small board on the inside of the envelope and screw it to the bigger board, with the 4 plastic tabs between the two boards.
6. To ensure the USB plug sealing, you can staple a small piece of bicycle innnertube.

Don't hesitate to post any questions or improvement you may think of. And don't forget to share your lamp once you've done it, with #solarlamp #lowtechlab !