Rechargeable batteries need battery chargers to top up their capacity to provide electric power. There are many different types of battery chargers available in the market, ranging from the small battery charger for nickel-cadmium (Ni-Cad) or nickel-metal hydride (Ni-MH) batteries to the deep-cycle battery charger used for the bigger automotive and marine batteries. A battery charger is usually designed for specific types of rechargeable batteries.

The battery charger designed for the rechargeable batteries in your portable electronic equipment is particularly helpful. With the portable battery charger handy, you can move around with your laptop, camcorder, cell phone, and similar electronic equipment secure in the knowledge that you can recharge them anytime.

Battery chargers use different methods of recharging batteries. There are fast battery chargers, trickle battery chargers, and stepped-voltage battery chargers. A trickle battery charger is considered the most gentle on your battery, while the fast or quick-charger is the harshest type of battery charger. A fast battery charger gives a constant current at higher amperage to finish charging relatively quickly.

You may need to make sure there is a match between your rechargeable battery and the battery charger. It is not prudent to use a Ni-Cad battery charger to recharge Ni-MH batteries. Certain rechargeable batteries are designed for fast battery chargers, whereas other batteries are meant to be charged by a slow, trickle battery charger. Using a fast battery charger on a battery designed for a trickle battery charger could damage the battery and shorten its life span.

The danger associated with recharging batteries is that you could forget about it and the battery gets overcharged. This will damage the battery; more importantly, it may lead to some overheating and, in some instances, cause the battery to explode. Some battery chargers use any or all of four techniques to prevent battery overcharge: peak detection, timer, individual cell control, and temperature. The principles used vary, but the function is the same, that is, to stop the flow of current once the battery charger has fully recharged your battery.

More recently, battery chargers based on pulse techniques have also been introduced into the market. This type of battery charger sends charge pulses to nickel-based batteries, with intermittent discharge pulses to improve the battery capability to accept the charge. This battery charger comes with a conditioning button to fully discharge your battery if you wish to before you begin recharging.

Even more convenient for you, there are so-called smart battery chargers which have the capability to charge more than one type of battery. Not only that, you can set the smart battery charger to charge at different rates as well.

That means it can act as a fast battery charger, which you may need if you are out doing a job with your portable electronic equipment. It can also act as a slow battery charger when you are under more relaxed circumstances and have the time to wait until your battery gets fully charged.

Usually, though, the smart battery chargers will charge your batteries at a fast rate when it is just beginning. It has sensors that tell it when the battery is nearing full charge. It then slows down the rate of charging down to a trickle-charge until the battery is fully charged. The smart battery charger then shuts itself off to avoid doing damage to the battery being charged.

Bear in mind that doing a fast charge on a cold battery is a very dangerous hazard associated with Ni-Cad batteries and can result in a violent explosion. You must allow cold batteries to reach room temperature first before you connect it to a battery charger.