by T.K. Hareendran:
Here is a tried and tested sample circuit of a Li-Ion battery charger that can be used to charge any 3.7V Li-Ion battery using a 5VDC (USB, Solar Panel…) power supply. At the heart of the circuit is one microchip MCP73831, available in SOT-23-5 package. MCP73831 is a highly advanced linear charge management controller for use in space-limited, cost-sensitive applications. This IC employs a constant current/constant voltage charge algorithm with selectable preconditioning and charge termination.
3.7V Li-Ion Battery Charger Circuit – [Link]
Standalone Linear Li-Ion battery charger with thermal regulation in ThinSOT application note (PDF!) from Linear:
The LTC4054 is a single cell lithium-ion battery charger using a constant-current/constant voltage algorithm. It can deliver up to 800mA of charge current (using a good thermal PCB layout) with a final float voltage accuracy of ±1%. The LTC4054 includes an internal P-channel power MOSFET and thermal regulation circuitry. No blocking diode or external current sense resistor is required; thus, the basic charger circuit requires only two external components. Furthermore, the LTC4054 is capable of operating from a USB power source.
App note: Standalone Linear Li-Ion battery charger with thermal regulation – [Link]
The bq2510x series of devices are highly integrated Li-Ion and Li-Pol linear chargers targeted at space-limited portable applications. The high input voltage range with input overvoltage protection supports low-cost unregulated adapters.
The bq2510x has a single power output that charges the battery. A system load can be placed in parallel with the battery as long as the average system load does not keep the battery from charging fully during the 10 hour safety timer.
The battery is charged in three phases: conditioning, constant current and constant voltage. In all charge phases, an internal control loop monitors the IC junction temperature and reduces the charge current if an internal temperature threshold is exceeded.
BQ25101H – 250-mA Single Cell Li-Ion Battery Charger, 1mA termination, 75nA Battery leakage – [Link]
Spacewrench over at Dorkbotpdx published a new build, a Power Playground project:
It’s a PMOS/NMOS H-Bridge with FETs that can handle 3 amps or so, plus a SPI current sensor, some switches & a rotary encoder (not stuffed yet), and a 7-segment display, all controlled by a Teensy-3.1 running FreeRTOS.
I made this because I’m always running into battery, power, inductor and transformer issues I don’t have any experience with. The idea is to use the H-bridge configuration and current sensors to experiment with moderate-current PWM, motor control, power-line synchronization, battery charging and discharging, etc.
Power playground project – [Link]
by Vladimir Rentyuk @ edn.com
Suppose that you need to test a 1.5V, AA-size alkaline battery. You can apply a short circuit and measure current, or you can measure open-circuit voltage, but neither method properly tests the battery. A suitable test current of approximately 250 mA gives you a more reasonable test. You can use a 6Ω resistive load at 1.5V, which produces an output voltage of 1.46V at an ambient temperature of 25°C if the battery is in excellent condition. A poor battery might produce less than 1.2V. Given the load, the output current at 1.2V will be 200 mA instead of 250 mA. The battery will have just 80% of a full load current. Instead, you can use the circuit in Figure 1 to produce a constant-current load.
Circuit provides constant-current load for testing batteries – [Link]
by DIY Hacks and How Tos @ instructables.com:
A “Joule Thief” is a simple voltage booster circuit. It can increase the voltage of power source by changing the constant low voltage signal into a series of rapid pulses at a higher voltage. You most commonly see this kind of circuit used to power LEDs with a “dead” battery. But there are many more potential applications for this kind of circuit.
In this project, I am going to show you how you can use a Joule Thief to charge batteries with low voltage power sources. Because the Joule Thief is able to boost the voltage of a signal, you are able to charge a battery with a power source whose output voltage is actually lower than the battery itself.
This lets you take advantage of low voltage power sources such as thermoelectric generators, small turbines and individual solar cells.
Joule Thief Low Voltage Battery Charger – [Link]
The LTC®3305 balances up to 4 lead acid batteries connected in series. All voltage monitoring, gate drive, and fault detection circuitry is integrated. The LTC3305 is designed for stand-alone operation and does not require any external control circuitry.
The LTC3305 employs an auxiliary battery or an alternative storage cell to transfer charge to or from each individual battery in the stack. A mode pin provides two operating modes, timer mode and continuous mode. In timer mode, once the balancing operation is completed, the LTC3305 goes into a low power state for a programmed time and then periodically rebalances the batteries. In continuous mode, the balancing operation continues even after the batteries are balanced to their programmed termination voltage.
LTC3305 – Lead Acid Battery Balancer – [Link]
If you´re deciding whether it´s worth to use a backup battery, we bring you a few remarks why to go for it or not.
Lithium battery Xeno Energy with a lifetime of over 10 years and rules for their usage were brought to you in our article „10 years of operation for 1 battery?”. They´re usable as a “main” power source for low power consumption devices and the second main field of their usage is a power supply backup. In contrast to the smallest cells used for PC memories backup (BIOS) for example, the types, which we keep in stock feature capacity of several Ah and they´re also able to provide a relatively decent current. That enables to use such battery also for a real operation of the device (MCU) during the power supply dropout.
Probably the main reason why not to use a backup battery is a doubt about higher production costs of a given device. However, when we look at the sales price in our e-shop, we find, that common PCB types like for example XL-050F AX (LS14250CNA) or XL-060F AX (LS14500CNA) are available for the price of max. 4 Eur/pce. At the same time, using this type of batteries eliminates the need for a battery holder, charging chip, etc.
The newest contribution on the field of PCB lithium batteries in our stock is the type XL-210F/STD 5,5mm, what´s the disc with 33mm diameter and only 6.6mm height, with leads to be soldered to PCB (THT). Low profile enables usage even in slim devices and everywhere, where common cylinder types are not suitable.
Further information will provide you the Xeno short form catalogue as well as detailed datasheets of Xeno batteries. In the Xeno production portfolio can also be found special batteries with a higher pulse capacity and type for extra high temperatures -55 to +130°C.
Backup battery soldered directly to a PCB? – [Link]
by micahmelnyk @ instructables.com:
In short: I developed a portable, battery powered device that sounds an alarm when your bag or purse is moved. Once armed, can only be turned off by your secret code.
The device is built off an Arduino compatible Trinket Pro, using an off-the-shelf project box with PCB.
Bag movement alarm for theft prevention – [Link]
by David Nield @ gizmag.com:
The batteries inside our smartphones and laptops are fighting a losing battle when it comes to keeping these devices juiced up, but researchers from ETH Zurich have discovered a new type of glass material that could make a major difference: vanadate-borate glass. The glass can be used as an electrode material in lithium-ion batteries to almost double the amount of time they last between charges.
A new type of glass could double your smartphone’s battery life – [Link]