Battery Types

There are, in general, two types of batteries: primary batteries, and secondary storage or accumulator batteries. Primary types, although sometimes consisting of the same active materials as secondary types, are constructed so that only one continuous or intermittent discharge can be obtained. Secondary batteries are constructed so that they may be recharged, following a partial or complete discharge, by the flow of direct current through them in a direction opposite to the current flow on discharge. By recharging after discharge, a higher state of oxidation is created at the positive plate or electrode and a lower state at the negative plate, returning the plates to approximately their original charged condition.

What is the best battery?

What is the best battery? Many people want to know the answer. Below is a summary of the strength and limitations of today's popular battery systems. Although energy density is paramount, other important attributes are service life, load characteristics, maintenance requirements, self-discharge costs and safety. Nickel-cadmium is the first rechargeable battery in small format and forms a standard against which other chemistry are commonly compared. The trend is towards lithium-based systems.

Nickel-cadmium- mature but has moderate energy density. Nickel-cadmium is used where long life, high discharge rate and extended temperature range is important. Main applications are two-way radios, biomedical equipment and power tools. Nickel-cadmium contains toxic metals.

Nickel-metal-hydride- has a higher energy density compared to nickel-cadmium at the expense of reduced cycle life. There are no toxic metals. Applications include mobile phones and laptop computers. NiMH is viewed as steppingstone to lithium-based systems.

Lead-acid- most economical for larger power applications where weight is of little concern. Lead-acid is the preferred choice for hospital equipment, wheelchairs, emergency lighting and UPS systems. Lead acid is inexpensive and rugged. It serves a unique niche that would be hard to replace with other systems.

Lithium-ion- fastest growing battery system; offers high-energy density and low weight. Protection circuit are needed to limit voltage and current for safety reasons. Applications include notebook computers and cell phones. High current versions are available for power tools and medical devices.

What is a Battery?

"A battery can be any device that stores energy for later use. The word battery is limited to an electrochemical device that converts chemical energy into electricity, by use of a galvanic cell. A galvanic cell is a fairly simple device consisting of two electrodes and an electrolyte solution. Batteries consist of one or more galvanic cells. "

"A battery is an electrical storage device. Batteries do not make electricity, they store it. As chemicals in the battery change, electrical energy is stored or released. In rechargeable batteries this process can be repeated many times. Batteries are not 100% efficient - some energy is lost as heat and chemical reactions when charging and discharging. If you use 1000 watts from a battery, it might take 1200 watts or more to fully recharge it. Slower charging and discharging rates are more efficient. A battery rated at 180 amp-hours over 6 hours might be rated at 220 AH at the 20-hour rate, and 260 AH at the 48-hour rate. Typical efficiency in a lead-acid battery is 85-95%, in alkaline and NiCad battery it is about 65%."

Exam or ability

Nowadays when the graduated students set foot in society, they may face a big challenge in hunting a job. A large number of them may go to interviews with all certification. Although many people say that ability is more important than any kinds of certification, many companies will give the interview chance to the one who has more certification.

In my mind, the certification can not represent one’s ability in knowledge but the exam.

Now many students may try to pass a variety of exams in different areas that may help them in choosing jobs. Even if they have already passed the exam, they may not know it clearly. Some of them even totally lack of knowledge. On the opposite, some students know much more about it and have an ability to apply the knowledge, but they didn’t pass the exam.

Exam or ability, certification or ability, which will you choose?

laptop battery

When I was Fair and Young

--- Queen Elizabeth I

When I was fair and young, and favour graced me,

Of many was I sought, their mistress for to be;

But I did scorn them all, and answered them therefore:

"Go, go, go seek some otherwhere; importune me no more!"

How many weeping eyes I made to pine with woe,

How many sighing hearts, I have no skill to show;

Yet I the prouder grew, and answered them therefore:

"Go, go, go seek some otherwhere; importune me no more!"

Then spake fair Venus' son, that proud victorious boy,

And said: "Fine dame, since that you be so coy,

I will so pluck your plumes that you shall say no more:

'Go, go, go seek some otherwhere; importune me no more!'"

When he had spake these words, such change grew in my breast

That neither night nor day since that, I could take any rest.

Then lo! I did repent that I had said before:

"Go, go, go seek some otherwhere; importune me no more!"

laptop battery

AGM Absorbed Glass Mat Battery

Also known as Absorptive Glass Micro-Fibre

Its purpose is to promote recombination of the hydrogen and oxygen given off during the charging process. No silica gel is necessary. The fibreglass matt absorbs and immobilises the acid in the matt but keeps it in a liquid rather than a gel form. In this way the acid is more readily available to the plates allowing faster reactions between the acid and the plate material allowing higher charge/discharge rates as well as deep cycling.

This construction is very robust and able to withstand severe shock and vibration and the cells will not leak even if the case is cracked.

AGM batteries are also sometimes called "starved electrolyte" or "dry", because the fibreglass mat is only 95% saturated with Sulfuric acid and there is no excess liquid.

Nearly all AGM batteries are sealed valve regulated "VRLA".

This is an alternative recombinant technology to also used in VRLA batteries to promote recombination of the gases produced during charging. It also reduces the possibility of spillage of the electrolyte. Prone to damage if gassing is allowed to occur, hence charging rates may be limited. They must be charged at a slower rate (C/20) to prevent excess gas from damaging the cells. They cannot be fast charged on a conventional automotive charger or they may be permanently damaged.

SLI Batteries

This is the typical automotive battery application. Automotive batteries are designed to be fully charged when starting the car; after starting the vehicle, the lost charge, typically 2% to 5% of the charge, is replaced by the alternator and the battery remains fully charged. These batteries are not designed to be discharged below 50% Depth of Discharge (DOD) and discharging below these levels can damage the plates and shorten battery life.