Bryon Moyer writes:
The development of wireless sensing technology has made possible tasks that would have been unthinkable in years past. Sensors can be installed where it is impractical or impossible to run a communication wire; their ability to communicate wirelessly, as long as they are within range of a hub, means that it is possible to gather data in places or situations that were previously inaccessible.
The inability to run a communication wire to the sensor also means no power line as well. Sensors need power both to sense and to communicate, so that has typically meant using a primary battery. While you would presumably select a battery with as long a life as possible, the battery is still unlikely to outlast the life of the sensor, meaning that someone will have to go out and replace the battery at some point – which can be expensive.
Managing the Energy and Lifetimes of Thin-Film Batteries - [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]
This is a simple li-ion charger without a dedicated li-ion charger IC. This circuit can be used to efficiently and intelligently charge any single cell Li-ion battery pack like mobile battery, digicam battery, etc.
- Charging via mini-USB connector which is very common.
- Charging status display by LED
- Simple circuit by using opamp, resistor, and not by any complex dedicated IC or micro-controller.
- Charges completely drained (0V) battery packs.
- Max charging current 500mA (limited by USB supply), depending on battery.
Simple USB DIY Li-ion battery charger - [Link]
Planning on powering that next über-low-power board of yours from a measly CR2032 coin cell? Read this app note to understand exactly what the limitations of coin cells are: [via]
When designing a small wireless sensor node to be powered by the popular CR2032 coin cell, some sources claim there is a 15mA “limit” and that drawing more current is not possible or will “damage” the battery. This may give the impression that at 15mA everything works perfectly and battery capacity is great, while at 16mA nothing works. There is little public information available to explain why such a limit exists (if it indeed does exist), and little information explaining why 15mA would be a “magic number”.
Understanding Coin Cell Limitations - [Link]
Maxim describes various SMPS regulator topologies for battery powered systems. Isolated and non-isolated topologies are covered:
This tutorial presents an overview of regulator topologies for battery-powered equipment. The discussion covers linear regulators, charge pumps, buck and boost regulators, inverters, and flyback designs. The importance of peak current is explained, and schematics of each topology are shown.
Switch mode regulators for battery powered systems - [Link]
Steven Keeping writes:
Lithium-ion (Li-ion) batteries have become popular for portable electronics such as laptop computers and smart phones because they boast the highest energy density (capacity per unit volume) of any commercial battery technology. Other benefits include thousands of recharges and no occurrence of the “memory effect” that plagued early nickel cadmium (NiCd) rechargeable cells.
However, it has been a tough design challenge to get the technology to where it is today. Lithium is a highly reactive material that can, for example, burst into flames if it comes into contact with water. Engineers and scientists have worked hard to develop novel compounds that can leverage the advantages of lithium while producing inexpensive, reliable, and safe batteries.
A Designer’s Guide to Lithium Battery Charging - [Link]
Brian Chu writes:
Batteries often serve as the main energy source for portable electronic devices. Although they depend on batteries, portable consumer electronic products, such as GPS devices and multi-media players, often consume energy directly from an ac-dc wall adapter or accessory power adapter (or “Auto Adapter”) when the battery is low or the device is in a stationary mode. Due to their cost effectiveness over their useful life, rechargeable batteries are often used for the power source of the portable electronic device. Attributes such as “relatively high energy density” and “maintenance free” make Lithium-Ion (Li-Ion) batteries popular in the portable consumer electronic products. Refer to the application note, AN1088, “Selecting the Right Battery System For cost Sensitive Portable Applications While maintaining Excellent Quality” (DS01088) for characteristics of Li-Ion batteries. Some examples of how to properly design with Li-Ion batteries will be discussed in this application note.
Designing A Li-Ion Battery Charger and Load Sharing - [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]
A little known feature of Arduinos and many other AVR chips is the ability to measure the internal 1.1 volt reference. This feature can be exploited to improve the accuracy of the Arduino function – analogRead() when using the default analog reference. It can also be used to measure the Vcc supplied to the AVR chip, which provides a means of monitoring battery voltage without using a precious analog pin to do so.
Secret Arduino Voltmeter – Measure Battery Voltage - [Link]
A Switch Mode Power Supply circuit collection from Linear Technology. It covers 12 basic SMPS circuit categories: Battery, Boost, Buck, Buck-Boost, Flyback, Forward, High Voltage, Multioutput, Off Line, Preregulator, Switched Capacitor and Telecom. [via]
Switching regulator circuit collection - [Link]