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23 Jul 2013


by Fran Hoffart:

A circuit that properly charges sealed lead-acid batteries ensures long, trouble-free service. Fig 1 is one such circuit; it provides the correct temperature-compensated charge voltage for batteries having from one to as many as 12 cells, regardless of the number of cells being charged.

The Fig 1 circuit furnishes an initial charging voltage of 2.5V per cell at 25°C to rapidly charge a battery. The charging current decreases as the battery charges, and when the current drops to 180 mA, the charging circuit reduces the output voltage to 2.35V per cell, floating the battery in a fully charged state. This lower voltage prevents the battery from overcharging, which would shorten its life.

Charger extends lead-acid-battery life – [Link]

20 Jul 2013


Vladimir Rentyuk writes:

A TL431 shunt regulator is a perfect choice for many applications. You can use it as a comparator with hysteresis by taking advantage of its inner voltage reference along with few additional components. You can use this comparator with hysteresis, like a Schmitt trigger, as a simple battery monitor (Figure 1). You calculate the threshold voltage, VT+, of this comparator as VT+=VREF×(1+R1/R3), where VREF, the internal reference voltage of shunt-regulator TL431, is 2.5V.

Shunt regulator monitors battery voltage - [Link]

18 Jul 2013


This Design Idea describes a 9V battery-voltage monitor whose total parts cost less than 34 cents (Figure 1). You configure transistor Q1 as a 10-mA current sink. LED1, a Kingbright WP7104IT, is on when the battery voltage is good.

Configure a low-cost, 9V battery-voltage monitor - [Link]

13 Jul 2013


Texas Instruments is one of the most dominant technology companies ever. Behind Intel and Samsung, it is the world’s third largest producer of semiconductors. In addition, they are the largest manufacturer of digital signal processors and analog semiconductors. Young students may just know of TI as producers of their world famous graphing calculators. However, for the older, more experienced students, they quickly learn TI has technology that can be found everywhere. In fact, many of the ICs used for basic electronics are all created by TI.

There is also one additional area TI’s technology excels at. That would be in energy efficient electronics. One of the more popular devices is the MSP 430 microcontroller family. These MCUs allow developers to create embedded applications, which can manage power extremely efficient. The CPU can work with speeds up to 25 MHz or can be lowered to save power in applications. More importantly, the MCU has a low power idle mode. When working in this mode the CPU will draw as little as 1 micro-Amp of current. Along with the low power capabilities, this MCU can also work with all the usual embedded electronics communication protocols and peripherals.

Texas Instruments releases new battery saving technology – MaxLife - [Link]

5 Jul 2013


Inspired by trees scientists at the University of Maryland have developed a nanobattery that uses tin-coated wood fibers to store liquid electrolytes. Replacing the lithium found in many rechargeable batteries by sodium makes the battery environmentally benign. Sodium doesn’t store energy as efficiently as lithium, so you won’t see this battery in your cell phone – instead, its low cost and common materials would make it ideal to store huge amounts of energy at once, such as solar energy at a power plant.

Existing batteries are often created on stiff bases, which are too brittle to withstand the swelling and shrinking that happens as electrons are stored in and used up from the battery. The researchers found that wood fibers are supple enough to let their sodium-ion battery with an initial capacity of 339 mAh/g last more than 400 charging cycles. This puts it among the longest lasting nanobatteries. [via]

Rechargeable Wooden Battery - [Link]

3 Jul 2013


3D printing a battery itself is a remarkable achievement. A 3D printing a battery as small as a grain of sand is a giant hurdle forward in both, 3D printing and battery technologies. That is exactly what researchers working at University of Illinois and Harvard have done. To achieve this process the researchers had to create their own custom 3D printing technology. Although there are many types of materials 3D printers can use, most print objects using small liquid droplets, which build upon one another to create the object from the bottom up. For the researchers this process was not sufficient to achieve their goals. Therefore, they designed a 0.03mm nozzle, which releases the liquid materials continuously in a fashion, which is similar to toothpaste being squeezed from its tube. In addition, the researchers also invented a 3D printing material that is electrochemically active, which ultimately allowed the printed battery to store and release charges.

Micro-battery is 3D printed - [Link]

17 Jun 2013


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]

14 May 2013


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]

5 Feb 2013


mic @ wemakethings.net writes:

For a long time I wanted to enter the 21st century by stopping using NiCad or NiMH batteries and upgrading to Lithium accumulators as they provide more power per volume and are cool in general. Constant flow of obsolete cell phones provides a nice source of reasonably high-performance batteries for free – I felt compelled to tap into this resource for my battery operated projects.

Open source Lithium battery charger modules - [Link]

4 Feb 2013


Kennith needed a 1A constant current lead-acid battery charger for his HAM radios so he writes:

Since the SLAs are relatively small, and I only need them charged between radio outings, I opted to build a 1A constant current charger, based on the 555 Battery Charger which won first place in the 555 Design Contest Utility category. Using a 555 is a rather clever way to get two comparators and a Set-Reset latch in a single 8DIP package, which is needed for the high and low trip points. The major difference between my design and Mike’s is that instead of using a relay like him, I use an LM317 as a constant current source to limit my batteries charge rate.

555 based constant current lead-acid battery charger - [Link]





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