Different types of primary or disposable batteries -- such as carbon zinc, mercury, alkaline, lithium, zinc air and silver oxide batteries -- are used to power different devices. Carbon zinc batteries are used to power toys, watches, flashlights and cameras. Mercury batteries and zinc air batteries are used in small electrical devices like pagers and hearing aids while lithium batteries are used to power memory storage devices, cardiac pacemakers and calculators. Silver oxide batteries are used in backup lighting, alarms and analog devices.
Power backup is important in case of power blackouts from the main power supply line or in remote areas where there is no power. Secondary or rechargeable batteries are used as alternative energy storage devices. This is because they can preserve lots of energy, commendable low-temperature performance and draw large amounts of energy. The energy drawn is used as power backup for electric vehicles, portable electronics and power tools like drills. These batteries provide backup for aircraft and automotive systems and UPS power sources. Fuel cells are used to power space crafts and their energy is used as an alternative power source.
Charging electrical devices can be done even in the absence of main power supply electricity. You can efficiently charge portable electrical devices like cell phones or cameras while traveling. You can do this by connecting the electrical device to the fuel cell of a vehicle using a charger.
Because a lot of energy is extracted at the same time from secondary cells like nickel-cadmium cells, charging portable electrical devices is simplified. Though the batteries and cells can charge portable electrical devices like cell phones, only a specific amount of energy can be extracted. It is therefore only possible to charge one electrical device at a time before the cell is recharged. Storage of fuel for these cells is external, which makes it easy to replace.