A battery charger is a device designed to push electrical energy through a secondary cell or a battery to recharge it.How does it work?A typical rechargeable battery can be charged many times. First you have to make sure you have the right type of battery that allows for recharging. From here, you connect the battery to the charger unit. Once a current starts to flow, the electrodes that have depleted out of the batteries are recharged and the battery’s energy is restored. It is important to cut off charging once maximum capacity is reached, or the batteries will have to expend the excess energy and will overheat, leading to risk of rupture, chemical leaks or sometimes even the explosion of the battery.Different types of rechargeable batteries respond best to different types of charging, therefore being able to pick a charger suitable for one type of battery may not work well with another. In other words, we should not charge a mobile phone with a car battery charger, but neither should we charge NiMH batteries with a nicad charger.Methods of Battery Charging:Lead- and lithium-based chargers operate on constant current constant voltage (CC/CV).Nickel-based batteries charge with constant current and the voltage is allowed to rise freely.There are battery chargers available for standard sizes, for example, AA, AAA, C, D and 9V. There are also battery chargers available for larger lead-acid batteries.Some battery chargers have slots for the smaller cells to be placed into for charging. These often fit straight into a plug socket for power. Other battery chargers come with crocodile clip connectors to connect to larger, lead-acid batteries.Features and benefitsCost effective: batteries can be reused multiple times, expanding their performance lifeEco-friendly for the environment as recharging batteries reduces the number going to landfillCharge several chemistries including lithium-ion, NiCd, NiMHSome will work in your car if they have an adapter, providing charging on the moveFast charging timesHandy lights that change colour to indicate completion