Since rechargeable batteries usually involve a higher initial cost than their non-rechargeable counterparts, it is important to know how long the rechargeable batteries are likely to last prior to purchase. While the answer depends on many variables including the device it is powering and the conditions under which it is used, there are also some general rules that can be followed to make the most of battery life. These rules differ for different kinds of rechargeable batteries.
There are four main types of rechargeable batteries used for consumer applications, with other battery compositions becoming more popular every day. Each of these has different properties that makes them suitable for different uses. They can be found anywhere electronics are sold, as well as online on eBay. By understanding the various aspects of battery life, the differences in various battery composition types, and how to care for rechargeable batteries, a user can buy rechargeable batteries with the confidence that they are worth the price.
Understanding Battery Terminology
It is possible to buy and use rechargeable batteries without knowing anything about battery life, but knowing a few terms allows a shopper to compare different batteries and get the best deal. Some concepts to be familiar with include charge cycles, low self-discharge batteries, voltage discharge curves, and current ratings.
Charge Cycles and Life Expectancy
The overall lifespan of a battery is expressed in charge cycles. One cycle is a complete discharge followed by a complete charge. It stands to reason that the life expectancy in years varies depending on the use to which the batteries are put. In general, rechargeable batteries can stand from 500 to 800 charge cycles. While urban legend has it that rechargeable batteries need to be completely discharged before they are recharged, the truth is that fully discharging a battery can do more harm than good. For this reason, most devices are designed to turn off when the battery has discharged 90 per cent, thus avoiding doing damage to individual cells.
Low Self-Discharge Batteries
Self-discharge refers to the loss of charge in a battery when it is not being used. Most rechargeable batteries lose between 1 and 5 per cent of their charge each day that they are in storage. Low self-discharge batteries are made to lose less charge in storage.
Voltage Discharge Curve
Non-rechargeable batteries decrease in voltage over their lifetimes. The decrease in voltage when it is graphed is called the voltage discharge curve. Rechargeable batteries often have a very different curve. Many maintain a fairly consistent voltage until they are almost completely discharged, at which point the voltage goes down. This is called a 'flat' voltage discharge curve.
Batteries are often advertised with a current rating in milliAmpere hours (mAh). This number refers to the capacity of the battery. It can be divided by the current requirements of any device to give an estimate of the length of time the battery lasts when fully charged. For example, suppose a battery rated 2000 mAh is used in a flashlight that pulls 500 mA of current. The battery can be expected to last 2000/500= 4 hours.
Types of Rechargeable Batteries
The first rechargeable battery was invented as early as 1859. It was Gaston Planté's lead-acid battery, a version of which is still used in some cars today. In more recent times, nickel metal hydride batteries, nickel cadmium batteries, and various lithium-based batteries have become common. Each has properties which make it useful in certain situations and undesirable in others.
Lead acid batteries hold relatively little charge in comparison with their weight and volume. However, they make up for their bulkiness by supplying high surge currents. They are also fairly cheap to produce, making them ideal for motor vehicles.
Nickel cadmium batteries were once widely used in all kinds of portable devices from cameras to power tools. They offer good capacity, cycle life, and performance, especially in low temperatures. However, due to the toxicity of cadmium, a metal used in the manufacture of these batteries, they have been heavily restricted in the EU. They have been replaced by NiMH batteries.
Nickel metal hydride batteries came into the consumer market at the end of the 1980s. They offer two to three times the capacity of nickel cadmium batteries, and do not have the same problems of toxicity. However, they have a high rate of self-discharge, sometimes losing up to 20 per cent of their charge in the first day if they are not used. For this reason it is recommended that NiMH batteries be charged a few hours before they are used. Another option is the low self-discharge NiMH batteries available on the market. These usually have a slightly lower capacity.
Lithium-based batteries are fast becoming the most popular battery type since they have a high capacity and can be very light and slim. Lithium ion batteries are used in cell phones, laptops, and many other portable devices. Another type of lithium battery, the lithium ion polymer battery, is also becoming popular because it can be made in any shape and is flexible. It is often abbreviated 'Li-Po'.
Taking Care of Rechargeable Batteries
By following a few simple rules, battery users can make their rechargeable batteries last much longer. Using the correct battery charger is just the first step. Next, it is important to account for the break-in period with new batteries, and learn to store batteries correctly. The battery memory effect, and the effects of overcharging and deep discharge are also worth mentioning.
Use the Correct Charger
Using the wrong type of charger is dangerous and can potentially cause the batteries to explode. This is because different battery compositions need to be charged in different ways. Some batteries can be charged with fast chargers, while others are better off being charged with trickle chargers. Always make sure the charger is compatible with the battery composition.
New rechargeable batteries often have a break-in period during which they do not perform at full capacity. In particular, the charger may indicate that the batteries are fully charged when they are only partially charged. This is normal and does not mean the charger or the batteries do not work. In general, rechargeable batteries can take up to four full charge and discharge cycles before they perform at full capacity. The exception are LSD (Low Self-Discharge) batteries which ship fully charged. Always follow the manufacturer's instructions when charging for the first time.
Lithium ion batteries can be left unused for much longer than other battery types. However, all batteries self-discharge over time. When using batteries that self-discharge rapidly, such as regular NiMH batteries, make sure to charge them at intervals of a few months in order to maintain their capacity.
Battery Memory Effect
The so-called "memory effect" applies mainly to Ni-Cd batteries, although the term is now used for all kinds of rechargeable batteries. It refers to the decline in capacity that a battery may exhibit over time. As the theory goes, batteries decline in capacity faster if they are only partially discharged when they are recharged. However, the memory effect has only been reproduced with aerospace-style sintered-plate nickel cadmium cells, a special kind of cell not used in consumer applications.
What is often referred to as battery memory, is probably actually due to a number of other characteristics of rechargeable batteries, and has little to do with recharging partially discharged batteries. In particular, repeated overcharging can cause a similar effect to occur.
Overcharging Rechargeable Batteries
Overcharging batteries may cause voltage depression, which causes the battery to act as if it has lowered capacity. Voltage depression occurs when the voltage of the battery suddenly drops even though it is fully charged. Trickle chargers tend to often overcharge batteries, so make sure to remove the batteries at the right time to avoid this inconvenience.
Deep Discharge Issues
The 'memory effect' legend has caused many people to frequently discharge the battery completely before recharging. Unfortunately, this type of behaviour can be potentially harmful to the battery over the long term. Deep discharge causes cumulative damage to individual cells and should therefore be avoided. Fortunately, most devices shut off before the battery is completely discharged, in order to avoid repeated deep discharge from occurring.
How to Buy Rechargeable Batteries on eBay
Buying rechargeable batteries on eBay can be made to be easy and fast. Simply go to any eBay home page and enter the search term 'rechargeable batteries' in the search box. Follow the links to the appropriate subcategory where you can search using advanced search criteria. These criteria include brand, type, chemical composition, and quantity among other criteria. By checking the appropriate boxes, you can find just the batteries you need for any applications.
eBay's public seller feedback scores make it easy to find reputable sellers. Just click on the seller's name, or feedback score, to see their feedback history. Sellers with high scores typically have an award icon next to their names, and are labelled as 'eBay top-rated sellers'. You can even refine the search to show only listings by top-rated sellers, to ensure that you only do business with sellers who offer excellent customer service and fast shipping. As with any transaction, make sure to check the return policy and read the entire listing carefully.
Buying rechargeable batteries involves taking the plunge and spending more on batteries and a charger than one would spend on regular non-rechargeable batteries. However, rechargeable batteries typically turn out to be more affordable over the long run, since they can easily last for several years. Battery life depends on various factors that must be noted prior to purchase. Before shopping for rechargeable batteries, one should know the terminology used to describe the battery life of rechargeable batteries. Next, one has to become familiar with the various battery types, from lead acid batteries to lithium ion batteries.
Finally, there are several guidelines to help batteries to perform at their very best, and to get the most life out of them. Once these techniques have been understood, anyone can search for and find rechargeable batteries on eBay without too much effort at all. eBay makes it easy on potential customers to find the right rechargeable batteries, with advanced search options and seller feedback scores made easily available to the shopper. By understanding the factors that affect battery longevity, one can buy rechargeable batteries knowledgeably and with confidence.