Friday, 15 January 2016

Simple 2.7V 200mA USB Battery Charger Circuit

Today we are going to learn how to make a 5V 200mA or more amperage USB Battery Charger circuit for NiCd battery or power source circuit

This is a simple charger circuit for nickel-cadmium battery (NiCd) that can be connected in your USB port of computer or laptop.

The charging scheme employs only a constant current charging.

The two NiCd cells are connected in series and charge at 200mA current. Charging current is controlled by zener diode D1 and resistor R1. We can increase or decrease the current by using the approximate equation:
Current = VD1/R1; where VD1 is the zener voltage.

The use of D2 diode is to limit the voltage across the battery terminals, thus protect the battery from damage. Charging time of the fully discharged battery is given by the formula:
Time = Battery rating / 200mA ; where Battery rating is in mAH.
Example: battery rating 220mAh;
Time = 2200mAH / 200mA = 11 hours; meaning do not let battery charged more than 11 hours.

Part List:-

D1, D2 - BZX84C2V7, 1N5223B, or any 2.7V zener diode 1Watt

R1 - 10 ohms 1/2Watt

R2, R3 - 2 kilo ohms 1/4Watt

Q - 2N2907, 2N4403, or any similar PNP transistor

Make the above circut and enjoy charging. For any further querry please ask them in the comment section, i will be happy to help.

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