It is dangerous to charge an ordinary battery "Krona", "Korund" or similar. But rechargeable batteries are also produced in the same form factor. These include, for example, 7D-0, 125, "Nika" and numerous imported analogues.
Instructions
Step 1
Check out the pinout of the Krona battery. For the battery itself or a battery of this type, as well as for the power supply that replaces it, the large terminal is negative, the small terminal is positive. For the charger, as well as for any device powered by the "Krona", the opposite is true: the small terminal is negative, the large terminal is positive.
Step 2
Make sure the battery you have is actually rechargeable.
Step 3
Determine the charging current of the battery. To do this, divide its capacity, expressed in milliampere-hours, by 10. You get the charging current in milliamperes. For example, for a 125 mAh battery, the charging current is 12.5 mA.
Step 4
As a power source for the charger, use any power supply that has an output voltage of about 15 V and the maximum allowable current consumption does not exceed the charging current of the battery.
Step 5
Check out the pinout of the LM317T stabilizer. If you put it with the front side with the marking facing you, and the leads are down, then there will be an adjustment lead on the left, an outlet in the middle, and an inlet on the right. Install the microcircuit on a heat sink, which is isolated from any other live parts of the charger, since it is electrically connected to the output of the stabilizer.
Step 6
The LM317T microcircuit is a voltage regulator. To use it for other purposes - as a current stabilizer - connect a pull-up resistor between its output and the control output. Calculate its resistance according to Ohm's law, taking into account that the voltage at the output of the stabilizer is 1.25 V. To do this, substitute the charging current, expressed in milliamperes, into the following formula:
R = 1.25 / I
Resistance will be in kilo-ohms. For example, for a charging current of 12.5 mA, the calculation would look like this:
I = 12.5 mA = 0.0125A
R = 1.25/0, 0125 = 100 Ohm
Step 7
Calculate the power of the resistor in watts by multiplying the voltage drop across it, equal to 1.25 V, by the charging current, also previously converted to amperes. Round the result up to the nearest standard series.
Step 8
Connect the plus of the power supply to the plus of the battery, the minus of the battery to the input of the stabilizer, the regulating output of the stabilizer to the minus of the power supply. Between the input and the regulating output of the stabilizer, connect a 100 μF, 25 V electrolytic capacitor with a plus to the input. Shunt it with ceramic of any capacity.
Step 9
Turn on the power supply and leave the battery to charge for 15 hours.
