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]
The LTC4120 from Linear Technology is an all-in-one receiver chip for wirelessly charging battery-powered devices. It measures 3 x 3 mm and requires a pick-up coil at its input and a rechargeable battery at its output. A voltage is induced in the coil when it is in close proximity to the transmitter coil of a separate charging unit.
As well as the convenience of just placing your cell phone on a charging pad, this method is also ideal for hand-held devices that can’t use a conventional plug-in charger for reasons of hygiene or harsh/volatile atmospheres.
The battery charging functions allow for both constant current and constant voltage modes and a programmable float voltage level between 3.5 and 11 V accommodates a wide range of cell chemistries. An external resistor sets the charge current up to a maximum of 400 mA. It senses cell voltage and can initiate a low-voltage preconditioning phase if necessary. [via]
LTC4120 – Novel Contactless Battery Charger Chip - [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]
kmpres @ instructables.com writes:
My urge to build this project came when my wife’s car refused to turn over after a three day weekend away. Here in Tokyo, during winter, the temperature can drop to the low 20’s (F) at night and since we have no garage, her car just has to endure the cold as best it can. Many people don’t realize that you don’t have put up with repeated jump-starts or run to the nearest garage and plunk down 7,500 yen ($85) for a new battery every time this happens. Your old battery may just have built up a layer of lead sulphate crystals on its plates and that is preventing the acid from contacting them over their full surface area. This is caused by subjecting the battery to long periods of insufficient charge, as in the cases of unplugged golf carts over the winter, infrequently used automobiles, and PV systems that don’t get enough sunlight to charge their batteries. The result is a great reduction in the battery’s ability to produce electricity.
Desulfator for 12V Car Batteries, in an Altoids Tin - [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]
Abel Raynus writes:
Rechargeable NiCd (nickel-cadmium) cells are widely used in consumer devices because of their high energy density, long life, and small self-discharge rate. As a part of one project, I needed to design a reliable and inexpensive charger for a battery pack containing two NiCd AA-size 1200-mAh cells. In the process of the charger design, I needed to solve two main problems: first, setting a proper charge-current value, and second, stopping the charging process when the cell is full to avoid overcharging. This Design Idea describes a way to overcome both problems.
Charge a nickel-cadmium cell reliably and inexpensively - [Link]
by Abhijeet Deshpande:
Properly maintained rechargeable batteries can provide good service and long life. Maintenance involves regular monitoring of battery voltage. The circuit in Figure 1 works in most rechargeable batteries. It comprises a reference LED, LEDREF, which operates at a constant current of 1 mA and provides reference light of constant intensity regardless of battery voltage. It accomplishes this task by connecting resistor R1 in series with the diode. Therefore, even if the battery voltage changes from a charged state to a discharged state, the change in current is only 10%. Thus, the intensity of LEDREF remains constant for a battery state from a fully charged state to a fully discharged state.
Simple battery-status indicator uses two LEDs - [Link]