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This is a simple12 V Battery Charger Circuit Diagram is a high performance charger for gelled electrolyte lead-acid batteries. Charger quickly recharges battery and shuts off at full charge. Initially, charging current is limited to 2A. As the battery voltage rises, current to the battery decreases, and when the current has decreased to 150 mA, the charger switches to a lower float voltage preventing overcharge.

When the start switch is pushed, the output of the charger goes to 14 V. As the battery approaches full charge, the charging current decreases and the output voltage is reduced from 14 V to about 12 5 V terminating the charging. Transistor Ql then lights the LED as a visual indication of full charge.

The LP2951 regulator is manufactured by National Semiconductors. The choice of values is from an application note Battery Charging, written by Chester Simpson. Diode D1 can be any diode from the 1N00x series, whichever is conveniently available. It functions as a blocking diode, to prevent a back flow of current from the battery into the LP2951 when the input voltage is disconnected. Charging current is about 100+mA, which is the internally-limited maximum current of the LP2951. For those wondering, this is compatible with just about any single-cell li-ion battery since li-ion can generally accept a charging current of up to about 1c (i.e. charging current in mA equivalent to their capacity in mAh, so a 1100mAh li-ion cell can be charged at up to 1100mA and so on).

Li-Ion Battery Charger Circuit Diagram

A lower charging current just brings about a correspondingly longer charge time. IMHO 100mA is quite low, low enough that the schema can be used for an overnight charger for many typical single-cell li-ion batteries. The resistors are deliberately kept at large orders of magnitude (tens/hundred Kohm and Mohm range) to keep the off-state current as low as possible, at about 2?A. Resistor tolerances should be kept at 1% for output voltage accuracy. The 50k pot allows for an output voltage range between 4.08V to 4.26V - thus allowing calibration as well as a choice between a charging voltage of 4.1V or 4.2V depending on the cell to be charged. The capacitors are for stability, especially C2 which prevents the output from ringing/oscillating.

Parts List

IC1 = LP2951, voltage regulator
D1 = 1N4002, General purpose diode
R1 = 2M, 1%, metal-film
R2 = 806K, 1%, metal-film
P1 = 50K, potentiometer
C1 = 0.1uF, polyester
C2 = 2.2uF/16V, electrolytic
C3 = 330pF, ceramic

Mobile phone chargers available in the market are quite expensive. The schema presented here comes as a low-cost alternative to charge mobile telephones/battery packs with a rating of 7.2 volts, such as Nokia 6110/6150.

Mobile Phone Battery Charger Circuit Diagram

The 220-240V AC mains supply is down-converted to 9V AC by transformer T1. The transformer output is rectified by BR1 and the positive DC supply is directly connected to the charger’s output contact, while the negative terminal is connected through current limiting resistor R2. D2 works as a power indicator with R1 serving as the current limiter and D3 indicates the charging status. During the charging period, about 3 volts drop occurs across R2, which turns on D3 through R3.

An external DC supply source (for instance, from a vehicle battery) can also be used to energies the charger, where R4, after polarity protection diode D5, limits the input current to a safe value. The 3-terminal positive voltage regulator LM7806 (IC1) provides a constant voltage output of 7.8V DC since D1 connected between the common terminal (pin 2) and ground rail of IC1 raises the output voltage to 7.8V DC. D1 also serves as a power indicator for the external DC supply. After constructing the schema on a veroboard, enclose it in a suitable cabinet. A small heat sink is recommended for IC1.

This is a simple Electronic Rf Type Battery Charger Circuit Diagram. This type of charger couples RF from L2 to an external pickup coil. The pickup coil connects to a rectifier and battery to be charged. This idea is handy because no wire or contacts are required. L2 is 10T #24 wire and L3 is 10T #30 wire. Both coils are mounted on a 1 V ferrite rod.