If that doesn't sound risky enough, the improper transportation of some batteries can be a federal offense. Of course, things aren't all bad.
In fact, rechargeable batteries are getting safer, cheaper, and more powerful all the time. For today's handheld DV camcorders, power requirements are about half that of older, shoulder-mount cameras, so batteries are smaller, lighter, and longer-lasting, too.
Nevertheless, when considering your power needs and matching them to products now on the market or soon to be, you should consider several factors, including the following:
• your equipment's technical requirements and operating parameters
• the technical, chemical and electrical specifications of the entire power system (batteries, chargers, accessories)
• the usual price/performance and warranty considerations. You may find that one—or more—power options are required.
The Type Cast
Each of the main rechargeable battery types has its own characteristics, be it Nickel Cadmium (NiCad), Nickel Metal Hydride (NiMH), Lithium Ion (Li-Ion), or hydrogen fuel cell. One of the biggest differences is the power/weight ratio. NiMH has about twice the capacity of NiCad—more power, less weight. Li-Ion batteries produce the same energy as NiMH batteries but weigh even less.
NiMH batteries are more environmentally friendly than NiCads. They do not contain toxic materials like cadmium or mercury.
NiCad (and even NiMH) batteries suffer from "memory effect." If only partially used (or discharged) before recharging, a battery "forgets" it can discharge anymore, and an artificial baseline is created. The battery still works, but may only hold a portion of its original capacity.
In the past, users were often encouraged to run through a battery's full cycle (charge, discharge, charge) every couple of weeks, usually by letting a device run on battery power until no more remains. More and more, however, sophisticated charger systems will do this for you, and eliminate most traces of false memory. It's a matter of some debate, in fact, whether the real cause is chemistry, poor manufacturing techniques, or improper charging techniques. In any case, new technology is addressing this once aggravating issue.
All batteries, however, do self-discharge (depending on battery type and storage conditions, primarily), so a good battery management system that involves some sort of charge/discharge, use/maintenance protocol is recommended.
NiCad batteries are very resilient, and few storage considerations are needed. They work well if fully charged a few days before use (watch for moderate self-discharging and adjust cycle times if needed). It's good if you can fully discharge them at least every five to seven uses.
NiMH batteries should be charged on shooting day (they have a fairly high self-discharge rate). They should be discharged every 30-odd uses, just to be safe. Store them charged, and charge them up every couple of months anyway, even if they have not been used for a while.
Li-Ion (and the older lead acid-type) batteries do not develop memory effect. They have a fairly slow self-discharge rate, so can be topped off a few weeks before use (they handle long-term storage well; keep them at around 40% capacity, and they can sit happily for months). Li-Ions probably charge up the slowest of all, however.
One of the newest battery types is based on hydrogen, a lighter-than-air gas. When hydrogen is properly mixed with oxygen inside portable cartridges, electricity is released—and lots of it. Hydrogen fuel cells offer extended runtimes at reduced weights in comparison with other solutions.
They are not so much recharged as refilled (hydrogen is also available in solid form, as metal hydride, and so cell packs can be swapped easily), and are considered a very "clean and green" power source.