Home page » Digital Cameras

Search:

Refine search for Digital Cameras

Nickel-Metal Hydride
One of the most popular alternatives to NiCd is Nickel-Metal Hydride (NiMH), first developed in the 1980s and in widespread use today. NiMH technology is similar to NiCd, but uses a special alloy in place of the highly toxic cadmium metal for the negative electrode. This is less environmentally damaging when the battery is eventually discarded, and also gives them an energy density as much as three times higher, making them ideal for many portable devices, as well as some of the latest generation of electric vehicles.

NiMH batteries are available in all common sizes, with the most popular being the AA and AAA sizes used in hand-held devices. As popularity of mobile gadgets has grown over the past few years, the charge capacities of NiMH batteries have increased dramatically, with 2700mAh (milliamp-hour) AA-sized cells now widely available, which is a huge improvement over the 600-800mAh capacity of a typical AA-size NiCd battery. Anecdotal evidence suggests that NiMH batteries are less prone to the “memory effect”, especially if charged up using a special electronic charger that monitors the battery’s performance and occasionally “refreshes” it.

NiMH batteries are not without their disadvantages however. Their “shelf life” when fully charged is lower than most other rechargeables, losing as much as 10 percent of their charge within 24 hours, and then around one percent per day thereafter, with the highest capacity batteries having the poorest shelf life. However there are newer types of NiMH batteries that have been introduced over the past couple of years that have vastly improved long-term storage, with as much as 85 percent of charge being retained after 12 months. These types of batteries are often sold fully charged as an alternative to alkaline primary batteries.

NiMH batteries are not as durable as some other types, with a lifespan of around 500-1000 charge cycles, with a wide variation depending on how the batteries are used.

There is also a potential problem when a group of NiMH batteries are used together, as is usually the case in electronic devices such as digital cameras. If one battery of a group becomes fully discharged before the others, it may become permanently damaged by an effect called “polarity reversal” where the other batteries in the group drive the drained cell in reverse. For this reason it is important never to use NiMH batteries of different capacities together, and any group of batteries that is used together should be charged together.

NiMH batteries suffer from dramatically reduced performance in cold conditions, often appearing to be drained until warmed up, which limits their usefulness in gadgets that are commonly used outdoors.

Add your comment

© 2003-2009 TrustedReviews & IPC Media
About Us | Contact Us | Legal | Privacy | RSS