Table of Contents
Battery Part 1: About Batteries
Not too long ago battery was not essential to photography. Many cameras can just click away taking great photos without any battery and most professional cameras can switch to mechanical mode when their battery runs out. Today without a battery the best digital camera is nothing more than an expensive paper weight. It is almost impossible now to find a camera that doesn't require battery to operate. Every single feature and function of a camera depends on battery for power.
At one time digital camera was marketed to new users as a cost-saving over film camera because it has no "running cost", but soon many new digital camera users discovered that their new digital camera literately EAT batteries and they ended up spending quite a sum on batteries for their new digital camera! Batteries are also becoming more intelligent: they always seem to know when you don't have a spare battery with you or you are without a charger. When those conditions met, the battery would fail you at that very moment when you desperately needed their services! So it is time we get to know them and understand their behaviour, their needs and wants in order to get the best from your camera.
A battery is a container of chemical with two electrodes of different conducting materials.
Before we go any further let's clarify some basic terms used in our discussion of battery. We call the first one energy capacity (for simplicity we use this term here; other technical manuals and websites may call it differently). This is how much energy a battery delivers and for how long, and is measured by mAH or milliampere-hours.
The battery power is produced by chemical reaction. If we draw current from the battery faster than the chemical reaction can take place the battery may produce so much heat that it wastes energy and shortens the battery life and results in lower overall mAH than what's stated by the manufacturer. At low current level some of the chemical reaction become wasted energy and not actually utilised to deliver the required current and the net result is also lower overall mAH than that stated. As such the mAH rating should only be used as a guide for rough estimate of how long a battery lasts or for comparison when selecting batteries.
The second term we define here is power density. This is how much usable power that can be called up quickly from the battery when required at any moment at a given voltage. For instance, in a set time frame if you can draw 1000 milliamp from battery "A" at a fixed voltage of 1.2V as compared to only 500 milliamp from battery "B" at the same voltage then, battery "A" is said to have twice the power density of battery "B".
Digital camera requires battery with good power density because the power requirement of a digital camera is high surge and high power drain. A mid-end digital camera consumes an average of 250 milliamp just to have it turned on. It consumes up to five times that amount if the LCD screen is also turned on and as much as 2000 milliamp during image processing immediately after a picture is taken. If a battery doesn't have the required power density to deliver this amount of power, it will result in over-heating of the battery. The voltage will drop below the minimum required to operate the camera and the battery likely to deplete its full power immediately.
If the last two paragraphs sound confusing for some of our readers, well, we'll try to rephrase and simplify it further here. Say we compare a digital camera to a car - the energy capacity is your fuel tank capacity so how far your car can travel depends on the capacity of your fuel tank and similarly, how many shots you can take with the battery depends on the battery's energy capacity. The power density is like the torque or "pick-up power" of your car. If you sit ten big fat people in your car and still manage to accelerate from 0 to 100MPH in 8 seconds then you would say the car or fuel has good "pick-up". So when your camera demands high power in a short moment like just as when a picture is taken and if the battery can deliver it instantly without any complaint then it is said that the battery has high power density.
We are almost done with defining the term with just one more to go - this last one is called the self-discharge rate. It is the natural loss of battery power or energy capacity when the battery is standing idle and not in use. The rate at which this takes place is called the self-discharge rate.
On Battery Part 2: Types of batteries we will take a look at the various types of battery available for photography and digital photography in general.
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