Here is circuit diagram of the Nicad Battery Charger. It use IC LM317T ( Hot IC) Control Current less 300mA, Size battery 2.4V,4.8V,9.6V.It Low cost circuit.
This is a NiCAD battery charger circuit. High-quality, Not necessary to have a full charge and cut, Because this circuit charges with constant current and voltage regulated. But this circuit is not difficult and cheap.
The basic principles of a NiCAD Battery charging. There are a number of ways, as follows.
1. A constant current.
The Nicad battery can provide current 500mA-hr charge rate that is 1/10 of the current capacity. Therefore should be charged with a constant current 50mA for 10 hours, but actually want to charge for 14-16 hours because when near full current to charge less. So lasts longer.
– In the NiCAD battery charger for fast charging current to about 100mA charging rate for 3-5 hours. But it has the disadvantage of charging, when the battery is fully charged, it must be removed, otherwise the chemical substances in the battery will be very hot and damage.
– But a slow charger will not do, because it can withstand heat.
2.A constant voltage or Fixed voltage regulator
The NiCAD battery, each battery has a voltage 1.2V, when it is fully charged voltage 1.25-1.3V. Therefore, we are charging a battery, the plus the voltage additive, such as 4 pieces, then the charging voltage 1.2×4 = 4.8V. But the charge like this, at first, a very high current flow. So, the voltage between NiCAD battery charger and very different, may have caused overheating and damage.
3. The Current and Constant voltage.
Like this charging, devices little more than the two first, but high quality. The safest way, and the battery the voltage is required by the specifications. When fully charged, the charger can be left in, because there is no current flow, Because the the voltage between the battery as well.
– I so chose the charging current and Constant voltage.
A constant current.
I am using LM317 as a constant current. Determined by the R6. In the circuit be defined output current (Iout) is about 50mA. If you want to current different from this, you can find out the R6. = 1.25V / Iout
this circuit is designed for charging multiple pieces. So it can select multiple the voltage levels is S1.
– 3.1V be applied to 2 battery (2.4)
– 5.5V be applied to 4 battery (4.8V)
– 10.3V be applied to 6 battery (9.6V)
Which we use Q1(TIP31),Q2(C1815) And other equipment. Included circuit is maintained at a constant voltage. LED1 is used for the power on. T1 transformer size is 300mA.
The other parts please look in the figure circuit.
How to build. Friends can place the part in perforated board. Because this circuit has a few devices. You should check diagram well before use charge battery. Good luck.
Now I add The copper PCB layout as Figure 2 and the components layout as Figure 3.
though this circuit very old or very ancient, But still useful.
However, if this error please tell me.
Related circuits about battery chargers