Li-Ion/Polymer Shunt battery charger system with low battery disconnect (PDF!) app note from Linear Technology:
The LTC®4071 allows simple charging of Li-Ion/Polymer batteries from very low current, intermittent or continuous charging sources. A near zero current low battery latching disconnect function protects even the lowest capacity batteries from deep discharge and potentially irreparable damage. The 550nA to 50mA operating current makes charging possible from previously unusable sources. With its low operating current the LTC4071 is well suited to charge low capacity Li Ion or thin film batteries in energy harvesting applications. The unique architecture of the LTC4071 allows for an extremely simple battery charger solution, requiring just one external resistor.
Li-Ion/Polymer Shunt battery charger system with low battery disconnect – [Link]
Perhaps the most frequently used rechargeable batteries on the market nowadays – Lithium-Polymer (Li-Po) can be found also in our offer.
From the beginning of electronics, the world searches for an “ideal” rechargeable battery. So far such a battery doesn´t exist (maybe supercapacitors in the future), but Li-Po (Li-Pol) cells are quite near to an ideal in some aspects.
Very low self-discharge (approx. 5% / month), high voltage of a cell (3,7-3,8V average), high energy density and a low weight, considerably stable discharge voltage and a possibility to recharge anytime are one of the main advantages of Li-Po cells. Another benefits are advantageous flat shape, high variability in dimensions and a long lifetime. No wonder, that Li-Po cells have become no. 1 in consumer electronics, hand tools and in many industrial devices.
Perhaps the only drawback of these cells is their lower chemical stability at overcharging (in a corner case ending up with a fire). But that´s the case which is practically eliminated at a common operation with a suitable charging circuit (chip or a charger intended for Li-Po).
Basic principle at usage is not to exceed approx. 4.25V charging voltage and the battery is almost discharged at a voltage below approx. 3.0V (2.75V). On the very end of a discharge cycle, the inner resistance slightly increases, what can cause a slight heating of a battery at higher currents – it is a normal behavior. Charging is usually based on a method constant voltage/ limited current. In principle it´s possible to use the same chargers and charging circuits for Li-Ion as well as Li-Po cells.
At a usual usage and discharging to say 20-80%, Li-Po cells will reward you by a reliable operation and a long lifetime. Flat shape is ideal for various handheld equipment, as well for usage in flat enclosures. In respect to a low self-discharge it´s possible to use Li-Po cells even as a backup energy source.
In our offer can be found several several Li-Po types from company EEMB with a capacity of 130 mAh to 2000 mAh. Exact list of available types and datasheets can be found below this article. Upon request, we´re able to provide you also many other types.
Try the most favorite type of batteries – [Link]
Limpkin wrote this blog article about his tiny NFC Reader with a TRF7970A build, and he will be giving a few of them away:
The main components are:
– the USB-enabled ATMega32U4
– a connector for the NRF24L01
– a Lithium-Ion battery charger
– an NFC transceiver
– a proximity sensor
The main idea of this platform is to read NFC tags while keeping its power consumption low. The microcontroller is communicating with the NFC transceiver so you can use the platform as a standalone device or computer peripheral.
You could therefore control a switch (using the expansion header), send the tag data via RF (using a NRF24L01 you’d connect) or simply have the ATMega32U4 forward the read/write commands sent from your computer. The original idea was to support libnfc.
Tiny NFC reader with a TRF7970A – [Link]
I bought recently on yahoo auctions a set of 4 gameboys (1 brick, 2 colors and 1 pocket 1st gen) because I had a plan to hack them and I needed some guinea pigs. I have already 2 at home but … well, it was a total of 1,500 JPY (10 euro w/ delivery) so. Got them yesterday morning, quick check: all working modulo the inevitable sticky buttons or gunk that went everywhere after 15 years. Dismantle, wash (water & soap), remove glue (ugly pokemon stickers) and marker (acetone), dry, reassemble. Working fine, nice looking and that vomiting man-sweat smell is gone (previous owner must have had very sweaty hands).
Gameboy battery upgrade – [Link]
by Dario Borghino @ gizmag.com:
Scientists at the Nanyang Technological University (NTU) in Singapore have developed a smart window that is able to tint itself blue, partially blocking incoming light, without the need for an external power source. The device also functions as a small transparent battery that recharges on its own simply by interacting with the oxygen in its surroundings.
Self-tinting “breathing” window doubles as a transparent battery – [Link]
by EEVblog @ youtube.com:
Want to include a small Lithium Ion or Lithium Ion Polymer battery into your next project? It’s easy! Dave gives you the low down on how they work and how to charge them and select a suitable charging IC.
NOTE: For safety you should always use circuit protected cells as per the larger cell I was holding up. It protects against over-discharge, over-voltage, shorts etc.
(BTW, the reference to Lithium Ion Polymer being the same as Lithium Ion is in terms of charging, if that was not clear. The Ion Polymer type have polymer anode material and hence a different construction that allows the small pouch type cells shown in the video, and other thin odd shapes shown toward the end)
EEVblog #176 – Lithium Ion/Polymer Battery Charging Tutorial – [Link]
Jason over at Rip It Apart did a teardown of a Kentli PH5 1.5 V Li-Ion AA battery:
The PCB that holds the 1.5 volt regulator is inside the end cap, with the rest made up of the Li-ion cell itself. Curiously enough, the cell inside is labeled “PE13430 14F16 2.66wh” which is interesting in more than one way. First of all, the rated energy content of the cell is less than what’s on the outside label (2.66 watt-hours versus 2.8), and the cell inside is actually a Li-ion polymer (sometimes called a “Li-Po” cell) type; I was expecting a standard cylindrical cell inside. Unfortunately, my Google-fu was unable to pull up any data on the cell. I might attempt to do a chemistry identification cycle on the cell and see if TI’s battery database can bring something up.
Teardown of Kentli PH5 1.5 V Li-Ion AA battery – [Link]
by w2aew @ youtube.com
The Humanalight is a simple single-cell flashlight kit that will produce usable light, even from a “dead” AA battery. Circuits like these are often called a Joule Thief. This term has been applied to just about any circuit that allows you to boost the voltage from nearly depleted batteries for some other low-power application – such as lighting an LED. Strictly speaking, a Joule Thief circuit is an Armstrong style blocking oscillator that uses a bifilar wound transformer and relies on the saturation characteristics of the core to produce oscillation. This flashlight uses a simple two-transistor relation oscillator. A description of the circuit is given, and its operation is examined by viewing the waveforms on an oscilloscope. The proceeds from the sale of this kit benefit the “Ears To Our World” charity which provides self-powered radios and other technology to rural, impoverished and remote regions of the world.
Circuit Walkthrough: A single cell LED light – [Link]
by Afrotechmods @ youtube.com
A beginner’s guide to different battery chemistries and how to choose the right battery for your project.
How to choose a battery: A battery chemistry tutorial – [Link]
by Solarcycle @ instructables.com:
Power Stacker is a portable, modular, USB rechargeable lithium-ion battery pack. Stack them together for power hungry projects or separate them for smaller projects with this modular system. The Gerber, BOM, and .STL files are available below.
Power Stacker does what other USB rechargeable batteries have failed to do, and that’s the ability to combine together for increased battery capacity or separate in to many small batteries for smaller projects. You can literally use the same Power Stacker batteries for many years across many applications!
Stackable USB Rechargeable Battery System – [Link]