Here is a little help for organizing batteries for your photo/video equipment.
If your camera bag has an available pocket, perhaps you dedicate that pocket to loose batteries. If not, then maybe batteries haphazardly occupy nooks and crannies at the bottom of your bag. While I have often bundled four or more batteries using a simple elastic band, it has been unreliable; the band eventually breaks and the batteries randomly spill about.
My first solution is a filter pouch, which originally was included with a lens filter. Though the filter manufacturer never intended this little fabric pouch to hold a set of batteries, it functions well for that purpose. When empty, the pouch occupies almost no space in a pocket or in a bag. When full of eight Eneloop rechargables, it is still possible to loose the pouch entirely … which is my current dilemma. (I know it’s around here somewhere.)
The second solution is similar, but specifically designed to hold a set of batteries. The Indicator Pouch is divided into two compartments; each will hold four AA batteries or one camera battery, but a DSLR battery might be big enough that the Velcro closure isn’t entirely secure. Optionally, the green or red tag may be used to remind you whether the batteries are charged or discharged. Unlike my old filter pouch, the Indicator Pouch has belt loops on the back side.
Finally, I like Storacell plastic battery holders; see the introductory photo. Different models are designed specifically for different size batteries. Available in a variety of colors, I use orange for AAA and yellow for AA. The 12-cell AA holder is the perfect size to supply three speedlites.
A solution that I have not personally used is a plastic clamshell box for batteries. Vaguely, I imagine opening the clasp and then all the batteries simultaneously fall to my feet and roll across the floor.