Not every battery can be charged with a homemade charger. For example, it is dangerous to charge lithium-ion, lithium-polymer and similar batteries in this manner. But for nickel-cadmium and nickel-metal hydride batteries, such devices are quite suitable.
It is necessary
- - two batteries size AA or AAA;
- - double battery compartment, corresponding to the size of the batteries;
- - 5 volt power supply unit;
- - soldering iron, solder and neutral flux;
- - multimeter;
- - a light bulb for a voltage of 3.5 volts and a current equal to one tenth of the battery capacity.
Instructions
Step 1
Make sure you are actually rechargeable batteries, not batteries, and that they have a HiCd or NiMH electrochemical system.
Step 2
Correctly select the rated current of the light bulb. Divide the capacity of the batteries, expressed in milliampere-hours, by ten, and you will find out the current of the bulb in milliamperes. If the capacity of the batteries is converted into amperes before dividing, then the rated current of the bulb will also be obtained in these units.
Step 3
Connect the positive pole of the power source to the positive pole of the battery compartment through the light bulb. Connect the negative terminal directly to the negative terminal of the battery compartment. In the open circuit, turn on a multimeter operating in the DC milliammeter mode.
Step 4
If necessary, discharge the batteries so that there is one volt per battery. It is best to discharge them separately. To do this, use a load composed, for example, of bulbs suitable for voltage and current. In no case should the batteries be discharged with a short circuit and generally exceed the discharge current specified in their passport.
Step 5
Insert the batteries into the compartment, and they will automatically be connected in series. Turn on the power supply - the current-limiting lamp should light up. Check with a multimeter that the charge current is indeed equal to one tenth of the capacity. If this is not the case, select a light bulb with a correspondingly lower or higher charging current.
Step 6
Replace the multimeter with a jumper. Keep the batteries energized for fifteen hours. They are then ready to use.
Step 7
If it turns out that the batteries have lost their capacity, that is, even after fifteen hours of charging with a current equal to one tenth of their capacity, they are quickly discharged, they should be trained. To do this, it is necessary to carry out several alternating cycles of full charge and full discharge with a current equal to the charging current. Each time, the batteries should be discharged to such an extent that one volt is required for each of them.
