by deba168 @ instructables.com:
One year ago, I began building my own solar system to provide power for my village house.Initially I made a LM317 based charge controller and an Energy meter for monitoring the system.Finally I made PWM charge controller.In April-2014 I posted my PWM solar charge controller designs on the web,it became very popular. Lots of people all over the world have built their own. So many students have made it for their college project by taking help from me.I got several mails every day from people with questions regarding hardware and software modification for different rated solar panel and battery. A very large percentage of the emails are regarding the modification of charge controller for a 12Volt solar system.
Arduino solar charge controller and energy monitor - [Link]
by Steve Taranovich @ edn.com:
I have been hearing about so many different and novel techniques for battery charging and cell balancing lately. Designers are working feverishly to optimize cell balancing and battery safety along with improved efficiency. I have been closely watching Sendyne for a while now, ever since the SFP100 was chosen to be one of 2013’s EDN Hot Products and UBM ACE Award finalist in the category of Ultimate Products in Analog ICs. This IC is a current, voltage and temperature measurement solution and can be configured for automatic compensation for resistance dependence of the shunt over temperature with a separate reference design board.
Unique battery pack architecture patented by Sendyne - [Link]
by pinomelean @ instructables.com:
Lithium based batteries are a versatile way of storing energy; they have one of the highest energy density and specific energy(360 to 900 kJ/kg) among rechargeable batteries.
The downside is that, unlike capacitors or other kinds of batteries, they can not be charged by a regular power supply. They need to be charged up to a specific voltage and with limited current, otherwise they turn into potential incendiary bombs.
And that’s no joke, storing such a high amount of energy in a small and normally tight packaged device can be really dangerous.
Li-ion battery charging guide - [Link]
We all know lithium-ion batteries need careful monitoring to prevent over-charging and ensure cell temperature remains within limits. We all thought we knew the best way to replace the charge as well: trickle charge, take it nice and gentle to keep the cell temperature down and prolong cell life. Turns out we may have got that last one wrong! New findings published in the Nature Materials Journal by a team of researchers at Stanford University indicate that by tweaking the battery design it may be possible to get faster charge/discharge rates and also increase the number of charge cycles.
Better lithium-ion Charging - [Link]
Integrated Device Technology has released what is said to be the world’s smallest 2W contactless-charging power receiver chip. In the future when all our internet-connected portable and wearable devices need a recharge after a busy day with their head in the cloud, contactless charging will be the way to go. The IDTP9026 wireless-charging receiver chip has a board footprint of just 30 square millimetres and is designed to charge a standard lithium-ion battery rated at 4.2 V. An AD pin allows the device to be switched out of the charging circuit when an external adapter is used for recharging. A separate enable pin is also available to turn the device off.
Receiver Chip for Wireless-Charging - [Link]
Stephen Evanczuk writes:
Lithium-ion batteries have emerged as a common energy-storage device in many energy-harvesting applications. For engineers, maximizing battery performance and lifecycle requires use of battery charging circuitry able to account for the specialized characteristics of Li-ion cells. Engineers can cost-effectively build in Li-ion-charging functionality using available ICs from manufacturers including Analog Devices, Diodes Inc., Fairchild Semiconductor, Fujitsu Semiconductor, Intersil, Linear Technology, Maxim Integrated, Micrel, Microchip Technology, and Texas Instruments.
Unlike many other battery technologies, Li-ion cells require a charging profile maintained within a tight envelope. An undercharged Li-ion battery simply cannot provide its full rated energy output. On the other hand, charging circuits cannot afford to push Li-ion battery voltage above recommended limits or apply charging currents that exceed manufacturer-recommended levels. In either case, application of overvoltage or excessive charging current begins to break down Li-ion cells, reducing overall battery life or even resulting in catastrophic failures. For engineers, the challenge is maximizing charging rate and cell voltage without overcharging the cells.
Constant-Voltage/Constant-Current Devices Optimize Li-Ion Battery Charging for Energy-Harvesting - [Link]
Here is a montage of photos that I took while modifying my iPhone 4s to build in wireless charging. There are wireless charging options out there such as the powermat system but they all involve slipping on a jacket around the iPhone. I wanted to internalize the technology so that the beauty of the iPhone is not hidden away! It’s taken a while to complete but it’s finally done.
iPhone 4s Wireless Charging Hack - [Link]
Don Scansen writes:
For any complete energy-harvesting system designed to provide power to anything but small, short-duration loads, storage batteries represent a necessary but significant portion of the initial expense. The cost of batteries over the lifetime of the system can have an even larger impact if care is not taken to maximize the useful life of the battery component. What’s more, if unit growth continues for photovoltaic and other energy-harvesting systems relying on large-capacity storage batteries, designs that fail to maximize battery life could have a negative environmental impact due to the extra material and energy consumption needed to manufacture replacement systems as well as dispose of exhausted units.
Charge Controller Design for Maximum Battery Lifetime in PV Systems - [Link]
Electrical engineers of the University of Princeton are working on a cheap solar-powered charging system that can be printed on plastic and that transfers the produced electricity wirelessly. The solar cells are made from amorphous silicon (a-Si), a non-crystalline form of silicon. Crystalline silicon (c-Si) is much more efficient when it comes to converting sunlight into electricity but a-Si has the advantage that it can be processed at much lower temperatures (75 °C against 300 °C for c-Si), allowing it to be printed on plastic sheets.
The electric circuit is made out of the same material as the solar cells. And although a-Si has a lower electrical performance than c-Si, when it comes to producing cheap electricity-generating plastic sheet which can be put up anywhere, a-Si is best. By making the charging system available at a large scale, the Princeton engineers aim to have wireless electricity everywhere. [via]
Omnipresent Sun-Powered Wireless Charging Stations - [Link]
A photoflash unit is a Resistor-Capacitor circuit. It utilizes a fundamental property of capacitors. A capacitor opposes an abrupt change in the voltage and this ability of a capacitor is put to use.
Circuit design of a photoflash unit:
A photoflash unit has a simple circuit design: a high-voltage direct current (DC) supply is connected in series with a high-resistance resistor (which we’ll call ‘R1′). This resistor limits the current flow. A capacitor ‘C’ is connected in parallel with a flash lamp. The resistance ‘R2’ of a flash lamp is of small value. The circuit contains a switch between the large resistance ‘R1’ and a small resistance flash lamp ‘R2’, such that it can connect either resistance at any time during the process.
How does it work?
When the switch connects R1, the capacitor begins to become charged. The charging of a capacitor is time consuming due to a large ‘time constant’. The time constant is the product of the resistance ‘R1’ and the capacitance ‘C’, given by the following expression:
Time Constant = Resistance of large Resistance * Capacitance
T = R1*C
During the charging process, the potential of the capacitor starts rising gradually. Initially it has the value of zero but by the charging it rises to a steady value of ‘Vs’. As the voltage increases, the value of the electric current passing through it decreases from peak value to zero. This limiting of current happens due to the large resistance R1. The charging time of a capacitor is approximately equal to five times the time constant. That is;
Charging time of capacitor = 5*Time constant
The discharging process of a capacitor takes place when switch connects with the flash lamp (with small resistance ‘R2’). The low resistance of the flash lamp allows a high discharge electric current to flow in a brief period of time. The discharging time is almost five times the product of small resistance ‘R2’ and the capacitance ‘C’, given by the following relation:
Discharging time of a capacitor = 5* (R2*C)
The photoflash unit circuit emits a high current pulse of short duration during the complete charging and discharging process of this simple Resistor- Capacitor Circuit. Such an RC circuit has many other practical applications, including Radar Transmitter Tubes and Electric Spot Welding.