Rechargeable batteries wear out both during active use and simply during long-term storage. The way in which the battery capacity is restored depends on its electrochemical system.
Instructions
Step 1
Lithium batteries differ from all others in that they wear out least of all if they are constantly kept in a charged state. They do not have a memory effect, so feel free to put them on charge, without waiting for a full discharge. It is best to keep a phone with such a battery connected to the charger all the time while it is in the room - the controller built into the device will maintain the charge at maximum, but at the same time, prevent overcharging. Leaving home with your phone, unplug the charger from the mains so that it does not waste energy, and when you come in, put it back on charge again, regardless of the state of the battery. When it is worn out anyway, it cannot be restored. In a number of communication salons, having handed over an old battery for recycling, you can purchase a new one at a significant discount. The device for charging such a battery must be factory-supplied.
Step 2
Any other batteries must be discharged before charging to the voltage indicated in the passport, but in no case below it. Whether it is discharged too deep or when charging is started prematurely, capacity will be lost. If this happens, rebuild the battery by performing several slow charge / discharge cycles. Find the nominal (not the maximum!) Discharge current in the battery passport and connect a load to it that consumes just such a current. Monitoring the voltage at the battery terminals with a voltmeter, wait until the voltage drops to the minimum value specified in the passport. Immediately disconnect the load and start charging with the current specified in the passport for slow charging. Withstand the period indicated in the passport, then repeat the cycle several times. If the battery is not too worn out, its capacity should be restored to nominal.
Step 3
If the battery is accidentally discharged to a voltage below the minimum voltage, your further actions also depend on its electrochemical system. It is dangerous to charge a lithium battery in this state - it is possible for particles of lithium metal to form and ignite. And the charge controller, most likely, will not allow it to be charged. Take the battery to a recycling center. Batteries of other systems can be restored by connecting to a power source that allows adjusting not only voltage, but also current. Set the voltage a little more than the nominal voltage of the battery, and the current equal to the nominal charge current. Switch on the ammeter in series with the battery. It is possible that at the beginning, charging will not occur at all - the ammeter needle will not deviate even by one division. It's okay, leave the battery connected to the source for a day, periodically glancing at the device. If the current starts to increase, this can be considered a success. If it gradually increased to the nominal, and the source switched from voltage stabilization mode to current stabilization mode, the battery can be considered "cured". It remains to restore its capacity, as indicated in the previous step.
