The most commonly used types of batteries today are the nickel-cadmium, the nickel-metal hydride, the lithium-ion, and the lead-acid battery. Each of these batteries is used in different applications.
The first three are usually used in devices like cell phones and laptops, whereas the lead-acid battery is used for heavier applications that require a strong surge of power, such as the battery in a car that is used to start the vehicle, as well as batteries that store the energy from a solar installation, or batteries that provide the backup power that keeps crucial equipment functioning when the mains power fails.
Each of these batteries requires a different reconditioning process.
You may wonder why this is so, but the answer is really quite simple. Each type of battery performs basically the same function - Each type of battery stores and releases electrical energy using chemical reactions. The reason why the reconditioning process is different in the case of different types of batteries is that the chemical processes that store the electrical energy are quite different in each case
Reconditioning the Nickel-Cadmium battery
In the case of a nickel-cadmium battery, the reconditioning process is really extremely simple. All that is needed to restore this sort of battery is to do a complete discharge, and ensure that the battery has little or no residual energy left. After this, you have to fully charge the battery, and the majority of nickel-cadmium batteries will return to normal function after this reconditioning process.
It is even better if you use the reconditioning process as a standard maintenance procedure, and apply this deep discharge-recharge cycle to the battery at least four times a year.
Reconditioning a Nickel-Metal Hydride battery
The nickel-metal hydride battery also responds to a similar reconditioning process to the one I've outlined above, so we won't dwell on it too much.
Reconditioning a Lithium-Ion Battery
Next, is the lithium-ion battery, which is really very unstable, and which requires a special charger if one is to recondition it successfully. One needs to apply a low trickle current to a lithium-ion battery that has gone dead, and this will bring the residual charge of the lithium-ion battery above a certain crucial threshold.
Once the inherent charge of the battery crosses this threshold, the battery will charge and function normally, without any problems at all.
Reconditioning a Lead-Acid Battery
A lead-acid battery is a complex piece of work, and also one of the oldest kinds of batteries on the market today. The lead-acid battery suffers from an issue called sulfation, in which a layer of lead-sulfate forms over the lead plates inside the battery, and which prevents the battery from functioning properly.
This sulfation needs to be broken down if the battery is to function again. The problem is that you have to do this without actually damaging the plates of the battery. This can't be done physically without dismantling the entire battery, so we have to do it chemically. We'll do this with a mixture of distilled water and Epsom salt.
Boiling (distilled) water needs to be mixed with Epsom salt, and then the cells of the battery need to be drained of their electrolyte, and then replaced with this boiling mixture of Epsom salt - this will break down the sulfation inside the battery, and thus return the battery to function. It goes without saying, that there are a great many safety procedures involved here, so you need to know exactly what you're doing.