While having extras of these will save your tail in a pinch, it presents a problem on how to keep track of their usage. It does you no good to swap out a dead battery for another dead battery, or a full memory card for another full card. Here is a simple tip that I have learned along the way that can help you keep track of both batteries and memory cards. This is a top secret, professional tip. Are you ready? The answer is direction.
DirectionAll batteries and memory cards have a direction that orients it as being up or down, front or back. For example, typical round batteries have a positive and a negative terminal where the positive usually has a nipple and is considered to be the top. Camera batteries tend to have their terminals on one end and not the other. With batteries, keeping track of directions is easy enough, positive terminal on commercial batteries is up and terminals on camera batteries is up. Now that you understand this, this system will become easy. If the batteries are oriented up, they are good and ready to go. If the orientation is down, they are depleted and need recharging.
Memory cards can be tracked much the same way, terminals up or terminals down. My concern is that I like to protect the terminals, to a certain extent, on my memory cards. For these I tend to prefer the terminals pointing down and tracking them by their labels. Label up or label down. Just like batteries if the label is up it's ready to go. If the labels are down they are full. Just keep these in mind for now because we'll get back to them.
Storage SystemsThe easiest method of controlling batteries and memory cards is by utilizing some kind of container to keep them organized. Plastic cases and zippered wallets are two commonly used products. You can buy inexpensive plastic cases for just about any kind of battery. Zippered wallets are handy for storing both batteries and memory cards. I strongly suggest a zippered wallet for memory cards as their small size makes them real easy to lose.
"Aha!" I hear you exclaim in understanding. In other words, the storage system should have some mechanical means of being able to track what state the memory card or battery is in when stored. With a zippered wallet the tracking is fairly easy. Most wallets contain a pocket for storing batteries or memory cards. The opening become the control. If battery terminals are up, the batteries are charged and ready to go. If they are down into the pocket you know they are dead.
With Memory cards you should get pockets that are meshed as that will allow you to see if the labels are up or down. If labels are up you know you have a fresh card. If labels are down you know that card is full. While it seems obvious, having a consistent system will save time and aggravation when push comes to shove during a photo shoot. It also makes it easier when you get home. A quick glance tell you what batteries or cards to pull out and take care of.
In the illustration at right you can see the cases have been labeled with a blue marker. An arrow with the word charged let's you know that if a battery is in the up position the same as the label, that battery is fresh. A battery facing opposite the direction of the label and you have a spent cell.