• Remaining capacity
The first item is the remaining capacity of the installed battery. Special circuits and a memory chip in some batteries communicate the precise percentage of charge remaining in the battery, in 1% increments. Others use a graphic to indicate roughly how much is left.
• Shutter count
The second item on most screens is the ‘Shutter count’. This shows how many times the shutter has been fired for still images (movies are not counted) on this particular battery on this charge. When the battery is recharged the number is reset, so it cannot show you the total number of shots that the battery handled. The ‘Shutter count’ is useful as it shows you how many shots you are getting from a single charge of the battery. If this number starts dropping it is a sure sign that the battery condition is starting to deteriorate.
This feature is not included on the enthusiast camera models, such as the 800D.
• Recharge performance
The final and possibly most important information is the recharge performance. This shows the battery’s condition and its ability to supply power.
Photographers often think that you can buy a battery and it will last forever. This is not the case. Batteries have a finite number of times that they can go through a recharge and discharge cycle. There is no exact figure as lots of things influence the expected life of a battery, but it is generally agreed that they last for between 500 and 1000 recharge/discharge cycles.
One of the key factors that can affect battery life is constant topping up. Shooting a few images and then charging the battery will shorten its life far quicker than using the battery untilit is almost flat and then recharging it.