Sam Davis writes:
Individual solar-panel systems produce dc power for remote applications while also storing energy in a rechargeable battery supported by a battery-charger IC.
In non-utility grid applications solar panels produce dc power for emergency roadside telephones, navigation buoys, and other remote loads. Virtually all 12-V-system solar panels comprise a series of photovoltaic cells that have a maximum output power of less than 25 W. In producing this power the solar-panel system uses a battery to provide power when the panel is “dark.” The rechargeable battery can supply power for long periods of time, requiring a charger that can properly operate a solar panel.
Meeting this need is Linear Technology’s LT3652 monolithic buck-charger IC, which operates with a single solar panel. The IC uses average-current-mode control-loop architecture to provide constant current/constant voltage (CC/CV) charge characteristics with a programmable charge current. The charger can be programmed to produce a 14.4-V float voltage. Housed in a 3- × 3-mm DFN-12 package, the IC can charge a variety of battery configurations, including up to three Li-Ion/Polymer cells in series, up to four Lithium Iron Phosphate (LiFePO4) cells in series, and sealed lead-acid batteries up to 14.4 V.
Power-Tracking Battery-Charger IC Supports Solar-Power Systems - [Link]
The LTC3115-1 is a synchronous buck-boost converter that delivers up to 2A of continuous output current from a wide range of power sources from single-cell Li-Ion to 24V/28V industrial rails to 40V automotive inputs. The LTC3115-1′s 2.7V to 40V input and output range provides a regulated output with inputs above, below or equal to the regulated output. The low noise buck-boost topology incorporated in the LTC3115-1 provides a continuous, jitter-free transition between buck and boost modes, making it ideal for RF and other noise-sensitive applications that must maintain a low-noise constant output voltage with a variable input power source.
LTC3115-1 – 40V, 2A Synchronous Buck-Boost DC/DC Converter - [Link]
This is a very simple capacity tester. It consists of single resistor that discharges battery. Arduino measures the voltage drop across resistor. According to Ohm’s Law current = voltage/resistance. Every second value of current is divided by 3600 and summed up to get the capacity expressed in Ah (Amp per hour).
I have used two parallel connected resistors that total resistance is 6.9 ohm. Make sure that they have proper power rating, if you don’t want them to convert to smoke. If voltage across 6.9 ohm resistor is 3.7 V, then current – 0.54 A, power ~ 2W.
Arduino Lithium-ion battery capacity tester/discharge monitor - [Link]
Accutronics has launched two new lithium-ion batteries in its Intellion series of credit card sized batteries. Designed to provide a high level of functionality and safety the CC2300 and CC3800 batteries allow integration of smart lithium ion battery into handheld portable products with minimal effort and cost.
The batteries feature an active electronic protection system that prevents them from being overcharged, over discharged or short circuited and to ensure that the battery will remain safe if externally abused. In addition, they have an impedance tracking fuel gauge that constantly tracks battery status, providing information such as remaining battery capacity, state of charge, run time to empty, battery voltage and temperature. [via]
Smart Li-Ion Batteries the Size of a Credit Card - [Link]
This is an app note from Maxim describing how to protect your Lithium Ion batteries from reverse insertion into the charger. The circuit is a Li-Ion battery charger with an added analog comparator designed to detect when then battery is inserted the wrong way and disconnect it from the charger. [via]
Combining a linear-mode single-cell lithium-ion battery charger (MAX1551) with a comparator (MAX9001) and n-channel FET adds a layer of reverse-battery protection that protects a single cell lithium-ion battery charger and battery from damage due to backwards insertion
Protect your batteries from reverse insertion - [Link]
The circuit uses both op-amps of an LM358 to control the charging of a single cell lithium ion battery. Charging automatically stops when the battery is full, and it is possible to charge batteries that have gone below the undervoltage limit. Power is provided through USB or any other 5V source.
Simple USB DIY Li-ion battery charger - [Link]
The Texas Instruments bq28550 battery gas gauge provides current and voltage protection, and secure, SHA-1/HMAC authentication for single-cell Li-Ion battery packs. Designed for battery-pack integration, the bq28550 requires host microcontroller firmware support for implementation. A system processor communicates with the bq28550 using one of the serial interface configurations to obtain remaining battery capacity, system run-time predictions, and other critical battery information.
The bq28550 uses an accurate gas gauging algorithm to report the status of the cell. The gauge provides information such as state-of-charge (%), run-time to empty (min.), charge-time to full (min.), battery voltage (V), and pack temperature (°C).
Single Cell Li-Ion Battery Gas Gauge and Protection - [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]
nabil’s blog: Bike Computer V0.1 Build - [via]
I’ve build the first prototype of my bike computer and have been developing the firmware for a couple of weeks now. Everything except the temperature sensor, accelerometer, servo headers, and Li-ion fuel gauge have been populated.
There have been a few minor electrical bugs like forgetting resisters for the ISP programmer, but nothing too difficult to fix for the next prototype. The bigger problems have appeared in the software world. First, the I’ve filled all 32K of the ATmega memory mainly because of lengthy sensor configurations, USB libs and FATFS. Second, RAM has become an issue when processing things like NMEA strings or drawing complex graphics. I’ve realized there is no point in having a vibrant TFT LCD screen if the 16MHz ATmega can only achieve millisecond refresh rates, which is why I’ll probably switch to some ARM processor for the next prototype. Maybe I’ll go with the STM32F4 series.
Bike Computer V0.1 Build - [Link]
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]