By Steven Keeping:
Power management in portable devices is one of the toughest challenges faced by electronic engineers. The consumer demands instant response from their device, lots of functionality, and a large, bright and colorful touchscreen. Moreover, many of these portable devices now incorporate wireless connectivity that places further demand on the cell. And yet, the user expects the battery, a sensitive lithium ion (Li-ion) cell that requires careful recharging from a number of sources including USB sockets, to last for at least a day and then refresh quickly.
Designing a power management system to meet these conflicting problems is tough. However, there are some proven design techniques that help extend battery life. Moreover, the key semiconductor vendors have made life a little easier by offering power management units (PMUs) that integrate some, or even all, of the functionality needed for the efficient power supply of portable devices.
Design Techniques for Extending Li-Ion Battery Life - [Link]
This application note describes how to recycle lithium-ion (Li+) batteries from older devices for use in other electronic devices, such as toys. This can all be done without the need for a microcontroller (or the required software). One challenge is that the battery charger in these older devices cannot usually be reused. The designer needs to create their own charger circuit, which this application note explains how to do in detail.
Lithium-Ion Battery Recycling Made Easy - [Link]
This collection of circuits provides step-up voltage regulation for single cell and dual cell Alkaline, NiMH, and Li+ battery driven applications. Regulate your battery driven app with an efficient converter from Maxim.
Your battery-powered application needs regulation. This collection of circuits provides step-up voltage regulation for single- and dual-cell Alkaline, NiMH, and Li+ battery-driven applications.
A simple 1A step-up converter in a tiny WLP package that can be used in any single-cell Li-ion application. This IC provides protection features such as input undervoltage lockout, short circuit, and overtemperature shutdown.
The input voltage of these circuits range from 0.7V to VOUT and they have a preset, pin-selectable output for 5V or 3.3V. The outputs can also be adjusted to other voltages using two external resistors.
MIT has designed an ultra-low cost “flow” battery that it claims will store 10-times as much energy as lithium-ion while consuming 10,000 times less power, making it a candidate to meet the Department of Energy’s target of less than $100 per kilowatt-hour for grid-scale deployment. [via]
MIT’s flow battery simplifies rechargeable technology by eliminating the ion-exchange membranes. The lower solid graphite electrode reduces liquid bromine to hydrobromic acid, while hydrogen is oxidized at the upper porous electrode.
Flow Batteries Go Mainstream - [Link]
A team at the University of Illinois has unveiled a battery design which offers 10 times the energy density and 1000 times faster recharge time compared to current cell technology according to a paper in the Journal Nature Communications.
The battery uses a LiMnO2 cathode and NiSn anode but the real innovation is in the novel electrode design. The electrodes are fabricated using a lattice of tiny polystyrene spheres which are coated with metal. The spheres are then dissolved to leave a 3D-metal scaffold onto which a nickel-tin alloy is added to form the anode, and the mineral manganese oxyhydroxide forms the cathode. In the last stage the glass surface is immersed into a liquid heated to 300˚C (572˚F). The resulting structure massively increases the electrode surface area and reduces the clearance between the electrodes. [via]
New Battery Technology Charges 1000 Times Faster - [Link]
Fritz Weld writes:
Lithium-ion batteries are sensitive to bad treatment. Fire, explosions, and other hazardous condition may occur when you charge the cell below the margin that the manufacturer defines. Modern battery chargers can manage the hazardous conditions and deny operation when illegal situations occur. This fact doesn’t mean, however, that all cells are bad. In most cases, you can replace the discharged battery and increase your device’s lifetime. Figure 1 shows the circuit for testing battery packs.
Simple circuit indicates health of lithium-ion batteries - [Link]
Peter T Miller writes:
Like other simple, single-cell lithium-ion battery chargers, Microchip’s MCP73812 provides no means of indicating the charging status. You can remedy this situation by adding four components (Figure 1). Add one more LED, and you also get a charging-complete indication. This two-LED configuration has the added benefit that one of the LEDs is always on, providing an indication that the charger is powered.
Add charging status to simple lithium-ion charger - [Link]
Testing laptop battery: pinout, SMBus, charge capacity @ KuzyaTech.
As a result of visiting Hamfest, I ended up with a laptop to take apart – a fairly new Toshiba Satellite C675D with a broken screen. It’s not a Hamfest if you don’t bring home something to take apart of course! Today we’ll be testing the battery it came with to see if it’s salvageable.The date code says it was made in 11/2011.
Testing laptop battery: pinout, SMBus, charge capacity - [Link]
The LT3651 enables fast charging of Li-Ion/Polymer batteries by delivering up to 4A of continuous charge current with minimal power loss. This is due to its high efficiency switchmode topology, including on-chip synchronous MOSFETs. Its autonomous operation means no microcontroller is necessary and the device integrates an onboard C/10 or timer charge termination. The LT3651’s programmable input current limit with PowerPathTM control regulates charge current to maintain a constant supply current, preventing the input supply from collapsing.
- Wide Input Voltage Range: Up to 32V (40V Absolute Maximum)
- Programmable Charge Current Up to 4A
- Selectable C/10 or Onboard Timer Termination
- Dynamic Charge Rate Programming/Soft-Start
- Programmable Input Current Limit
LT3651 – Monolithic 4A High Voltage 1 Cell Li-Ion Battery Charger - [Link]
State-of-Charge Measurement for Lithium-Ion Batteries is an advanced task, but can be simplified using specific ICs able to measure accurate SOC of Li-Ion batteries. Stephen Evanczuk writes:
All energy-harvesting-based systems need energy storage for times when the energy cannot be harvested (e.g., at night for solar-powered systems). Rechargeable batteries ‒ known as “secondary” cells to differentiate them from “primary” or single-use cells ‒ are usually specified for this task.
For rechargeable batteries, however, battery management depends on the best possible measurement of what is known as the state-of-charge (SOC) of battery cells. For lithium-ion batteries, the characteristics of Li-ion cells complicate SOC measurement and can challenge engineers looking to maximize Li-ion battery lifetime. To simplify design of Li-ion battery management systems, engineers can leverage a variety of SOC measurement techniques supported in ICs from Atmel, Linear Technology, Maxim Integrated Products, STMicroelectronics, and Texas Instruments.
Advanced ICs Simplify Accurate State-of-Charge Measurement for Lithium-Ion Batteries - [Link]