Tag Archives: Battery

Rechargeable Magnesium Batteries – Safer And Cheaper Than Li-ion Batteries

Researchers at the University of Houston reported in the journal Nature Communications the discovery of a new design that significantly improves the development of a battery based on magnesium. Magnesium batteries are considered as safe resources of power supply – unlike traditional lithium-ion batteries. They are not flammable or subject to exploding – but their ability to store energy is very limited. But the latest discovery of the new design for the battery cathode drastically increases the storage capacity.

Energy diagrams for the intercalation and diffusion of Mg2+ and MgCl+
Energy diagrams for the intercalation and diffusion of Mg2+ and MgCl+ in magnesium batteries

In order to make magnesium batteries, the magnesium-chloride bond must be broken before inserting magnesium into the host, and this is very hard to do. Hyun Deog Yoo, the first author of the paper, said,

First of all, it is very difficult to break magnesium-chloride bonds. More than that, magnesium ions produced in that way move extremely slowly in the host. That altogether lowers the battery’s efficiency.

The new battery technology stores energy by inserting magnesium monochloride into titanium disulfide, which acts as a host. By keeping the magnesium-chloride bond intact, the cathode showed much faster diffusion than traditional magnesium batteries.

The researchers managed to achieve a storage capacity density of 400 mAh/g – a quadruple increase compared with 100 mAh/g for earlier magnesium batteries. This achievement even overpowered the 200 mAh/g cathode capacity of commercially available lithium-ion batteries. Yoo, who is also the head investigator with the Texas Center for Superconductivity at UH, confirmed this fact.

The cell voltage of a magnesium cell is only 1V which is significantly less than a lithium-ion battery which has 3.7V cell voltage. Higher cell voltage and high cathode capacity made Li-ion batteries the standard. Li-ion batteries suffer from an internal structural breach, known as dendrite growth what makes them catch fire. Being an earth-abundant material, magnesium is less expensive than lithium and is not prone to dendrite growth.

The magnesium monochloride molecules are too large to be inserted into the titanium disulfide using conventional methods. The trick they developed is to expand the titanium disulfide to allow magnesium chloride to be inserted rather than breaking the magnesium-chloride bonds and inserting the magnesium alone. Retaining the magnesium-chloride bond doubled the charge the cathode could store. Yoo said,

We hope this is a general strategy. Inserting various polyatomic ions in higher voltage hosts, we eventually aim to create higher-energy batteries at a lower price, especially for electric vehicles.

DIY Arduino Battery Capacity Tester

deba168 @ instructables.com writes:

I have salvaged so many old lap-top batteries ( 18650 ) to reuse them in my solar projects.It is very difficult to identify the good cells in battery pack.Earlier in one of my Power Bank Instructable I have told, how to identify good cells by measuring their voltages, but this method is not at all reliable.So I really wanted a way to measure each cell exact capacity instead of their voltages.

DIY Arduino Battery Capacity Tester – [Link]

Integrated 36V buck battery charger provides seamless backup power

By Graham Prophet @ eedesignnewseurope.com:

LTC4091 is a complete lithium-ion battery backup management system for 3.45V to 4.45V supply rails that must be kept active during a long duration main power failure. The LTC4091 employs a 36V monolithic buck converter with adaptive output control to provide power to a system load and enable high efficiency battery charging from the buck output.

Integrated 36V buck battery charger provides seamless backup power – [Link]

Carrageenan, a seaweed derivative, can stabilize lithium-sulfur batteries surprisingly

Lithium-sulfur batteries are suitable for both vehicle and grid applications as they are ultra-cheap, high-energy devices. Sulfur is a very low-cost material and the energy capacity is much higher than that of lithium-ion. So, lithium-sulfur is one chemistry that can possibly meet the demand for energy storage at a cheap price. However, the serious problem is, lithium-sulfur batteries suffer from significant capacity fading that makes them almost practically unusable. But, Lawrence Berkeley National Laboratory researchers’ recent surprising discovery could fix this problem.

Carrageenan is extracted from this red seaweeds
Carrageenan is extracted from this red seaweeds

The research team at Berkley Laboratory surprisingly found that carrageenan, a substance extracted from red seaweeds, acts as a good stabilizer in lithium-sulfur batteries. Better stability in a battery means more charge-discharge cycle and an extended lifetime. Gao Liu, the leader of the research team, said,

It (Carrageenan) actually worked just as well as the synthetic polymer—it worked as a glue and it immobilized the polysulfide, making a really stable electrode.

Lithium-sulfur batteries are already been used commercially in limited applications but the “critical killer” in the chemistry is that the sulfur starts to dissolve and creates polysulfide shuttling effect. Polysulfide shuttling is the primary cause of failure in lithium-sulfur (Li-S) battery cycling. To solve the problem, the research team was experimenting with a synthetic binder that holds all the active materials in a battery cell together.

A binder is like a glue and battery makers want this glue to be inert. The synthetic polymer Liu experimented with, worked remarkably well. The reason is, by chemically reacting with the sulfur, the binder formed a covalent bonding structure and was able to stop it from dissolving. This finding motivated the researchers to find a natural material that would do the same thing. Finally, they discovered that carrageenan has similar chemical properties as the synthetic polymer they used in their initial experiments.

Bekley Lab's researcher is working with advanced light source
Berkley Lab’s researcher is working with advanced light source

With this discovery to stabilize lithium-sulfur batteries­ Liu now wants to improve the lifetime of lithium-sulfur batteries even further. The target of the researchers is to get thousands of cycles from lithium-sulfur chemistry. They are striving to find answers to questions like after this polymer binds with sulfur, what happens next? How does it react with sulfur, and is it reversible? Liu said,

Understanding that will allow us to be able to develop better ways to further improve the life of lithium-sulfur batteries.

As lithium-sulfur batteries are much more lightweight, cheaper, and have higher energy density compared to lithium-ion batteries, they are ideal for airplanes and drones. Hence, Berkeley Lab researchers’ surprising discovery may be a game changer in the world of batteries.

Cell Phone Can Make Calls Without a Battery

Vamsi Talla at the University of Washington in Seattle build a mobile phone that can rely only on energy that it could harvest from its surroundings. Imagine if you can send SMS or make a call when you are out of battery. That’s what’s the team trying to achieve.

Ambient light can be turned into a trickle of electricity with solar panels or photodiodes. Radio-frequency TV and Wi-Fi broadcasts can be converted into energy using an antenna. A hybrid system using both technologies might generate a few tens of microwatts.

Cell Phone Can Make Calls Without a Battery – [Link]

6V Lead Acid Battery Charger using BQ24450

6V Lead acid (SLA) battery charger project is based on BQ24450 IC from Texas instruments. This charger project takes all the guesswork out of charging and maintaining your battery, no matter what season it is. Whether you have a Bike, Robot,  RC Car,  Truck, Boat,  RV, Emergency Light, or any other vehicle with a 6v battery, simply hook this charger maintainer up to the battery. The bq24450 contains all the necessary circuitry to optimally control the charging of lead-acid batteries. The IC controls the charging current as well as the charging voltage to safely and efficiently charge the battery, maximizing battery capacity and life. The IC is configured as a simple constant-voltage float charge controller. The built-in precision voltage reference is especially temperature-compensated to track the characteristics of lead-acid cells, and maintains optimum charging voltage over an extended temperature range without using any external components. The low current consumption of the IC allows for accurate temperature monitoring by minimizing self-heating effects.  In addition to the voltage- and current-regulating amplifiers, the IC features comparators that monitor the charging voltage and current. These comparators feed into an internal state machine that sequences the charge cycle.

6V Lead Acid Battery Charger using BQ24450 – [Link]

Solar Power Module v2

Chip McClelland @ hackster.io published his solar li-po battery charger based on MCP73871 to manage the solar and DC charging of the LiPo battery, TPS63020 Buck-Boost Converter and Maxim 74043 LiPo Fuel Gauge. He writes:

I build connected sensor which are often deployed in local parks where there is no access to utility power. Over the past couple years, I have been refining and testing my solar power modules and have arrived at this compact integrated design. I have a number of these deployed and they have been in continuous service for up to two years. I wanted to share this design in case it might be helpful for your projects. I would also greatly appreciate any input or suggestions on this design so v3 will be even better.

Solar Power Module v2 – [Link]

Fuel gauge needs no battery characterization

by Susan Nordyk @ edn.com

The MAX17055 single-cell fuel gauge from Maxim not only eliminates battery characterization, but also keeps SOC (state-of-charge) error to within 1% in most scenarios. With its ModelGauge m5 EZ algorithm, the device provides tolerance against battery diversity for most lithium batteries and applications. It also allows system designer’s to decide when to shut down the device when the battery gets low, maximizing device runtime.

As the battery approaches the critical region near empty, the ModelGauge m5 algorithm invokes a special error correction mechanism that eliminates any error. In addition, it provides three methods for reporting the age of the battery: reduction in capacity, increase in battery resistance, and cycle odometer.

Fuel gauge needs no battery characterization – [Link]

Simple circuit indicates health of lithium-ion batteries

Fritz Weld @ edn.com proposes a simple circuit to check li-ion battery health. He 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]

Simple circuit indicates a low battery

@ edn.com writes:

The Design Idea in Figure 1 indicates a low-battery condition in an audio test instrument that is powered by four AA cells. As the instrument was otherwise an all-discrete design, this same approach seemed more in keeping with the spirit of the project than the use of a single-sourced integrated circuit.

Simple circuit indicates a low battery – [Link]