Electronics-Lab.com Blog

Battery-Charging Controllers for Energy Harvesters by Jon Gabay:

Whether your energy harvesting application uses large solar panels with high voltages and currents or, more often the case, must make do with minute amounts of power derived from various other ambient energy sources, one thing is almost certain: some type of energy storage is on board, whether in the form of a small rechargeable lithium ion battery, a supercapacitor, or solid-state energy storage technology. For the engineer this means that not only do we need to design circuits to harvest and convert ambient energy, but we also have to include an energy-harvesting interface (and protection circuitry) as well as a charge controller. This article looks at single chip energy harvesting devices that also provide some form of charge control. It discusses the different conditions under which energy can be extracted as well as what to expect when trying to squeeze power out of the ambient environment. Finally, the article will present some typical integrated solutions for small-sized low-power energy-harvesting designs.

Battery-Charging Controllers for Energy Harvesters - [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]

New technology improves both energy capacity and charge rate in rechargeable batteries.

EVANSTON, Ill. — Imagine a cellphone battery that stayed charged for more than a week and recharged in just 15 minutes. That dream battery could be closer to reality thanks to Northwestern University research.

A team of engineers has created an electrode for lithium-ion batteries — rechargeable batteries such as those found in cellphones and iPods — that allows the batteries to hold a charge up to 10 times greater than current technology. Batteries with the new electrode also can charge 10 times faster than current batteries.

The researchers combined two chemical engineering approaches to address two major battery limitations — energy capacity and charge rate — in one fell swoop. In addition to better batteries for cellphones and iPods, the technology could pave the way for more efficient, smaller batteries for electric cars.

The technology could be seen in the marketplace in the next three to five years, the researchers said.

A paper describing the research is published by the journal Advanced Energy Materials.

“We have found a way to extend a new lithium-ion battery’s charge life by 10 times,” said Harold H. Kung, lead author of the paper. “Even after 150 charges, which would be one year or more of operation, the battery is still five times more effective than lithium-ion batteries on the market today.”

New technology improves both energy capacity and charge rate in rechargeable batteries - [Link]

KIT (Karlsruhe Institute of Technology) researchers have developed a new concept for rechargeable batteries. Based on a fluoride shuttle — the transfer of fluoride anions between the electrodes – it promises to enhance the storage capacity reached by lithium-ion batteries by several factors. Operational safety is also increased, as it can be done without lithium. The fluoride-ion battery is presented for the first time in the “Journal of Materials Chemistry” by Dr. Maximilian Fichtner and Dr. Munnangi Anji Reddy.

Lithium-ion batteries are applied widely, but their storage capacity is limited. In the future, battery systems of enhanced energy density will be needed for mobile applications in particular. Such batteries can store more energy at reduced weight. For this reason, KIT researchers are also conducting research into alternative systems. A completely new concept for secondary batteries based on metal fluorides was developed at the KIT Institute of Nanotechnology (INT). [via]

Fluoride increases storage capacity of rechargeable batteries - [Link]

By looking to Mother Nature for solutions, researchers have identified a promising new binder material for lithium-ion battery electrodes that could not only boost energy storage, but also eliminate the use of toxic compounds now used in manufacturing the components.

Known as alginate, the material is extracted from common, fast-growing brown algae. In tests so far, it has helped boost energy storage and output for both graphite-based electrodes used in existing batteries and silicon-based electrodes being developed for future generations of batteries.

The research, the result of collaboration between scientists and engineers at the Georgia Institute of Technology and Clemson University, was reported Sept. 8 in Science Express, an online-only publication of the journal Science. The project was supported by the two universities, as well as by a Honda Initiation Grant and a grant from NASA. [via]

Seaweed polymer may improve electrodes in Lithium-Ion batteries - [Link]

pocketBot – line follower from OStan on Vimeo.

PocketBot – a matchbox-sized line following robot – [via]

PocketBot project consists of three parts. The key part of the project is the robot itself – a tiny line following vehicle of a matchbox size. Furthermore, the robot is supported with an USB communication device and with a PC control application. Altogether, these three parts form a complex solution to the line following issue.

The robot was primary designed to fit into a matchbox. A homemade double-sided printed circuit board stands as the robot’s chassis at the same time. Robot is powered with two rechargeable lithium-ion button batteries wired in parallel (3.6V, 40mAh each). The Atmel ATmega8 microcontroller runs robot’s program, which is written in C. An 8-pin connector offers ISP and UART interface for programming and debugging, respectively.

PocketBot – a matchbox-sized line following robot - [Link]

California-based company Leyden Energy is currently working on developing a new type of chemistry for lithium-ion batteries. If these efforts succeed, then experts here may develop batteries that do not overheat like traditional ones do, leading to new applications.

One of the most exciting prospects is the use of Li-Ion batteries in electric vehicles. This could mean that the automotive industry might become more receptive to creating such vehicles in the near future. [via]

Non-heating lithium-ion batteries in the making – [Link]

Vane writes:

Today i created pcb for Lithium Ion / Lithium Polymer USB Battery Charger with MAX1811, and designed with eagle pcb software.

About Max1811

The MAX1811 is a single-cell lithium-ion (Li+) battery charger that can be powered directly from a USB port or from an external supply up to 6.5V. It has a 0.5% overall battery regulation voltage accuracy to allow maximum utilization of the battery capacity.

The charger uses an internal FET to deliver up to 500mA charging current to the battery. The device can be configured for either a 4.1V or 4.2V battery. The MAX1811 is available in a small 1.4W thermally enhanced 8-pin SO package.

PCB for USB Charger with MAX1811 – [Link]

Here is the simple Lithium Ion Battery Charger. Lithium Ion batteries pack a lot of power by weight compared to other types. There are 2 things that need to be handled differently than nicad on NiMH 1. They cannot be used as a direct substitute (even if they look like other AA’s) since they run at about 3.6 (or so) volts.2. They cannot be charged in the same way as nicad or NiMH. [via]

Lithium Ion Battery Charger – [Link]

This is a universal charger of Lithium Ion batteries based on Atmega8 microcontroller. As you may know, LiIon batteries have many advantages comparing to regular NiMh or NiCd. Main of them are: high capacity by weigh and volume, no memory effect, fast charge and so on. But these batteries require special charging algorithm. You cant plug to some voltage and expect them to charge. It needs non constant voltage and current during charging cycle. Charging generally follows these steps:

• Current control at the Max Charge Current is used until the battery voltage reaches the voltage threshold (normally 4.1 or 4.2 volts per series cell). The battery is about 70% charged at this point;
• The voltage is now controlled very accurately (this is very important) at the threshold voltage while the current drops off naturally. Once the current reaches the lower cutoff ( about 100 mA per parallel cell typically), charging is stopped after a top-off time delay.

Lithium ion battery charger for robotics - [Link]

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